GH4169D is an age-strengthened nickel-based superalloy designed according to the improved GH4169 superalloy, which has become a remarkable candidate material for aero engines' hot-end components. However, large columnar grains and obvious anisotropy of mechanical properties often occur in this superalloy, which is fabricated by conventional wire and arc additive manufacturing (WAAM). To solve these problems, hybrid arc and micro-rolling additive manufacturing (HARAM) has been proposed. HARAM operates by combining WAAM with the rolling process. Herein, GH4169D superalloy samples were fabricated by WAAM and HARAM. Further, microstructures and mechanical properties of the samples under different heat treatments were investigated. Results show that with micro-rolling applied, large columnar grains became finer. In addition, the tensile strength of HARAM-ed GH4169D was significantly improved compared with WAAM-ed GH4169D (48 MPa in the X direction and 90 MPa in the Z direction), and the anisotropy of mechanical properties of HARAM-ed GH4169D was effectively eliminated. Homogenization plus solution plus double aging heat treatment effectively eliminated Laves segregation phase and induced the recrystallization of HARAM-ed GH4169D, leading to more finer and uniform grains than those without heat treatment, thereby, making the comprehensive properties optimal (the tensile strength and elongation were 1366 MPa and 25.0% in the X direction and 1354 MPa and 24.6% in the Z direction, respectively).
The performance requirements for copper alloys are increasing with the rapid development of transportation, electrical, aerospace, and electronics in modern industry. Cu-Cr-Zr alloy has exceptional strength and electrical conductivity as typical precipitation strengthening copper alloy. Strength and conductivity are mutually exclusive properties. The goal of realizing the high strength and conductivity of copper is a crucial subject in modern copper industry development. In this study, the effects of cryorolling on the microstructure, mechanical properties, and electrical conductivity of Cu-1Cr-0.2Zr-0.25Nb alloy were examined and the effects of numerous aging processes on the type, morphology, and distribution of precipitates were investigated. The findings depict that the Cu-1Cr-0.2Zr-0.25Nb alloy primarily comprised the Cr phase, Zr-rich phase, Cr2Nb phase, and Cu matrix phase. The fcc Cr nanoprecipitates can be precipitated in Cu-1Cr-0.2Zr-0.25Nb alloy after aging at 450oC for 30 min. The bcc Cr nanoprecipitates can be formed after aging at 450oC for 300 min. After cryorolling and aging treatment, the mixed structures, such as nanoprecipitation phase, nanodeformation twins, and dislocations in the Cu-1Cr-0.2Zr-0.25Nb alloy are produced and this alloy demonstrates remarkable comprehensive properties. The tensile strength of 700 MPa and electrical conductivity of 73.29%IACS were attained for the cryorolled Cu-1Cr-0.2Zr-0.25Nb alloy after aging at 450oC for 30 min; after aging at 450oC for 300 min, the conductivity can reach 79.81%IACS, and the corresponding tensile strength, yield strength, and hardness are 646 MPa, 606 MPa, and 212 HV, respectively. Combining the experimental findings with the computations of contribution to strengthening, it can reasonably be inferred that dislocation and precipitation strengthening were the primary strengthening mechanisms of Cu-1Cr-0.2Zr-0.25Nb alloy.
TiAl alloys are highly promising for high-temperature structural applications in the aerospace and automotive industries because of their low density, excellent high-temperature strength, and resistance to creep and oxidation. Nevertheless, low-temperature brittleness and poor deformability are the main factors severely restricting the widespread application of TiAl alloys. The process of β-solidifying γ-TiAl alloys results in alloys that consist primarily of α2, γ, and B2 phases, and have superior hot workability. Further thermomechanical treatments are applied to achieve a fine microstructure and enhance the inherent ductility of γ-TiAl alloys. In this work, Ti-44Al-5Nb-1Mo-2V-0.2B alloy sheet with ultrahigh plasticity at 800oC was achieved by cross hot-pack rolling (CHPR) and one-step annealing processes. SEM, EBSD, TEM, and tensile methods were used to investigate the hot deformation behavior, and the effects of different rolling processes and heat treatments on the microstructural evolution and mechanical properties of the alloy. The results show that the CHPR sheet had a more highly uniform deformation microstructure along the thickness direction and sheet plane compared with that of a unidirectional hot-pack rolled (UHPR) sheet, which consisted of residual lamellar colonies and equiaxed γ, α2, and B2 grains at colony boundaries. The size of the residual lamellar colonies was significantly smaller and the content was lower in the CHPR sheet compared with the UHPR sheet. This was due to a large number of broken residual lamellae and complete recrystallization under the combined action of a bidirectional shear force and compressive stress during the CHPR process. The high-temperature flow-softening mechanisms of TiAl alloy in the CHPR process mainly included bending and kinked lamellae, β/B2 coordinated deformation, phase-transformation decomposition of α2/γ lamellar, and dynamic recrystallization induced by primary and secondary twinning. To achieve further grain refinement, subsequent annealing of the CHPR-processed TiAl alloy was performed at 1200-1340oC. A multiphase equiaxed microstructure with fine lamellar colonies was obtained at 1200oC and a nearly complete lamellar microstructure was obtained at 1340oC. Moreover, the room-temperature and high-temperature tensile properties of UHPR and CHPR sheets in the horizontal and vertical directions were compared with samples annealed at 1200oC. The tensile properties of the CHPR sheets were more uniform in both directions. The multiphase equiaxed microstructure obtained in the CHPR alloy annealed at 1200oC had the best strength-plasticity balance with a tensile strength of 624 MPa (515 MPa) and elongation of 1.32% (107.0%) at room temperature (800oC). According to the fracture behavior, the fracture mode of these alloy sheets was translamellar or cleavage fracture at room temperature. Conversely, the fracture mode changed to ductile fracture at 800oC, and the failure mechanism was mainly via microhole coupling. The fractures in the annealed sheets (1200oC) had small and deep dimples, indicating optimal tensile elongation. The uniform and fine lamellar structure and equiaxed microstructure can hinder crack propagation and achieve enhanced mechanical properties.
An AZ31 Mg alloy sheet with bimodal non-basal texture exhibits good formability at room temperature. However, its initial yield stress (YS) is relatively low during uniaxial tension along the rolling direction (RD) at room temperature, which limits its potential for further application. Recent studies have demonstrated that introducing {101¯2} extension twin (ET) through predeformation can improve the mechanical properties of Mg alloy sheets with a basal texture at room temperature. However, the predeformation process for Mg alloy sheets with non-basal texture has rarely been investigated, along with their subsequent plastic deformation behavior at room temperature. Therefore, to investigate the room temperature deformation behavior and microstructure evolution of an AZ31 Mg alloy sheet with bimodal non-basal texture after predeformation, this work exerted a 5% thickness reduction on the sheet via cryogenic rolling. Then uniaxial tension experiments at room temperature and microstructure characterization experiments were conducted to illuminate the effect of predeformation on the mechanical behavior and microstructure evolution of the fabricated sheet. The findings indicate that when loaded along the RD, the YS and fracture elongation (FE) of the predeformed sample are 212.5% larger and 56.9% smaller than those of the non-predeformed sample. When loaded along the transverse direction (TD), the YS and FE of the predeformed sample are 6.7% smaller and 37.9% larger than those of the non-predeformed sample. The difference in YS in the predeformed samples is primarily attributed to easier activation of basal <a> slip in grains with a TD texture component in the TD sample than in grains with a bimodal non-basal texture component in the RD sample. The difference in FE in the predeformed samples is due to the inhibition of the expansion of preexsiting {101¯2} ETs in the RD sample, resulting in the early occurrence of {101¯1} compression twins (CTs). In comparison, the expansion of preexsiting {101¯2} ETs can be effectively performed in the TD sample. Additionally, some {101¯1}-{101¯2} double twins (DTs) would be activated at the later stage of tensile deformation to sustain and/or accommodate local plastic strain.
Oil and gas resources have become strategic assets, highlighting the need to improve production efficiency. Segmented fracturing technology effectively addresses the challenge of low fracturing efficiency and is widely used in oil and gas extraction. Therefore, the demand for degradable fracturing materials has increased rapidly to enhance oil and gas production efficiency. Rapidly degradable fracturing materials must achieve high degradation rates, while maintaining strong mechanical properties to ensure effective petroleum fracturing operations. Building on previous research on as-cast Mg-8Li-4Gd-1.5Ni alloys that are known for their high corrosion rates, this study performed hot rolling at 250 oC, with deformations of 30%, 50%, 70%, and 90%. Further, SEM, TEM, tensile mechanical performance testing, electrochemical testing, and hydrogen evolution measurements were used to examine the microstructure, mechanical properties, and corrosion behavior of the alloys. Results indicated that the microstructure underwent continuous elongation during rolling, and the networked long-period stacking ordered (LPSO) phases gradually transformed into parallel fibrous structures. At a deformation of 90%, the elongated fibrous LPSO phases were fractured into shorter segments, accompanied by an increase in the size and number of gaps between the LPSO phases. Recrystallized structures developed during hot rolling, accompanied by the refinement of GdNi3 particles and an increase in the dislocation density. As the deformation increased, the tensile strength of the alloy initially increased and then decreased. The alloy exhibited the highest tensile strength of 217 MPa and an elongation of 17% at a deformation of 70%. In a 3%KCl solution, the mass loss rate, hydrogen evolution volume, and hydrogen evolution rate of the alloy increased steadily, as the deformation increased. At a deformation of 90%, the alloy exhibited the highest corrosion rates at 25 and 93 oC, with mass loss rates of 0.47 and 3.63 mg/(cm2·min), respectively. Compared with the as-cast alloy, the weight loss rate of the hot-rolled alloy at 25 oC increased by 30.55%, whereas at 93 oC, it was 7.72 times greater than at 25 oC. The corrosion current density reached a maximum of 5.34 mA/cm2 at 25 oC. The corrosion began with pitting and gradually transitioned to filiform corrosion. The corrosion extended along the rolling direction at higher deformations. The parallel distribution of LPSO phases inhibited alloy corrosion. However, at a deformation of 90%, the fracture of the LPSO phases increased the number of galvanic corrosion sites. This fracture and the larger gaps between the LPSO phases reduced the protective effect. In addition, the bending of the LPSO phases, fragmentation of the secondary phases, recrystallization, and increased dislocation density enhanced the chemical reactivity of the alloy, resulting in a gradual increase in the corrosion rate. Hot rolling increased the dislocation density, reduced the grain size, and induced recrystallization in the alloy. These microstructural modifications resulted in work hardening and grain refinement, thereby improving the mechanical properties of the alloy.
Compared with high-grade electrical steel, low-grade electrical steel has the advantages of low cost and high production quantity but low profits. Therefore, researchers often focus on studying high-grade electrical steel without phase transformation. The microstructure evolution of low-grade electrical steel is more complicated compared to high-grade steel due to the three transformation stages— casting, hot rolling, and final annealing—that are present between austenite and ferrite during their processing. During continuous casting, the <100> columnar grains commonly formed in the low-grade electrical steel cast slabs with phase transformation illustrate the characteristics of the pronounced transformation delay and suppression. In such conditions, the change in hot rolling temperature will cause diversity in hot-rolled microstructures and textures and affect the subsequent cold rolling and annealing microstructure and texture. Based on the previous studies on the effect of hot rolling processes on the transformation texture of industrial low-grade electrical steel and the observation of the transformation delay and suppression of columnar grains in cast slabs, this work further investigates the influence of the initial microstructures before cold rolling and cold rolling reduction on the transformation texture and explores the law of texture inheritance. In particular, the idea of retaining {100} texture using metastable ferrite hot rolling is proposed to improve magnetic properties. The results show that there are more {100} deformed grains in the hot-rolled plate heated at low temperature, and the {100} texture inheritance is obvious after cold rolling and transformation annealing, which effectively improves the magnetic properties. The {100} transformation texture is weakened with the increase in rolling reduction because the initial {100} grains gradually disappear with increasing rolling reduction. An analysis shows that although the {100} transformation texture induced by the surface effect is hindered by the alloying Al and P elements in the used industrial electrical steel, the favorable initial {100} texture produced using low-temperature hot rolling promotes the memory-type transformation texture. In addition, the transformation texture obtained at a high annealing temperature is still better than the recrystallization texture obtained at a low annealing temperature. The significance of these results lies in the possible future practice of enhancing {100} texture in hot rolled plate by metastable ferrite rolling to improve magnetic properties in final annealed sheets.
Eddy current loss, which produces Joule heat and reduces transmission efficiency, is inevitable when the magnetic coupling is running. Magnetic couplings with high electrical resistivity alloys, such as titanium alloy, have been proven to be effective in suppressing the eddy currents. The Ti-6Al-3Mo-2V-1Cr-2Sn-2Zr alloy sheet was a α + β titanium alloy for marine engineering with high specific strength and electrical resistivity, which was used in magnetic couplings to suppress the eddy currents. In this study, the effect of annealing temperature on the microstructure, mechanical properties, and electrical conductivity of the Ti-6Al-3Mo-2V-1Cr-2Sn-2Zr alloy sheet was investigated. The results revealed that the band structure was arranged along the rolling direction (RD), and the as-rolled titanium alloy sheet showed a typical T-type texture with the c-axis of the α phase approximately parallel to the transverse direction (TD). A considerable increase in tensile strength and decrease in elongation after α ＋ β region (850-920oC) annealing was thought to result from the strengthening of secondary α/β interfaces in the bimodal structure. Simultaneously, the α phase showed both T-type and R-type textures, which also resulted in higher yield strength along the TD of the sheet. Additionally, when the sheet suffered a β phase region annealing (950-1000oC), the elongation immediately decreased due to the coarseness and precipitation of the secondary α and grain boundary α phases, respectively. Meanwhile, the annealed sheet showed an R-type and a new B-type texture components with basal poles rotated 20°-30° away from the normal direction (ND) toward the RD under the influence of variant selection of secondary α phase. However, the yield strength along the TD was still higher than that in the RD, indicating that the effect of texture on yield strength anisotropy was reduced. Finally, the electrical resistivity analysis of the titanium alloy sheet indicated that the electrical resistivity along the RD of the sheet was higher when the band structure was formed and the c-axis of the α phase was concentrated in the TD. However, the disappearance of the band structure and the increase in the volume fraction of the R-type texture will reduce the anisotropy of electrical resistivity.
An AZ31 magnesium alloy sheet with bimodal non-basal texture exhibits better rolling performance at room temperature compared with that with a typical basal texture. However, the rolling performance of bimodal non-basal texture sheets under medium temperature conditions remains unexplored. Therefore, this study aims to elucidate the rolling behavior and deformation mechanism of bimodal non-basal texture sheets at 200 oC. Employing EBSD characterizations, the microstructural characteristics of rolled sheets with initial basal and bimodal non-basal textures throughout a multipass rolling process were systematically investigated. Results showed that at medium temperature, the rolling performance of sheets with bimodal non-basal texture improved only slightly compared with those with basal texture. Especially, edge cracks were observed in deformed bimodal non-basal texture sheets after the fifth rolling pass, with a corresponding accumulative thickness reduction of approximately 48.0%. In contrast, sheets with basal texture exhibited edge cracks after the fourth rolling pass, with a corresponding accumulative thickness reduction of approximately 43.6%. A large number of basal <a> and non-basal dislocations (including prismatic <a> and pyramidal <c + a> dislocations) as well as a small number of {1011}-{1012} secondary twins were activated during the rolling deformation of basal texture sheets. These dislocations cause extensive dynamic recrystallization (DRX) near grain boundaries and twin interfaces, with the corresponding DRX volume fraction reaching as high as 47.9%. For bimodal non-basal textured sheets, in addition to the activation of high-density dislocations at the beginning of rolling deformation, an extensive {101¯2} extension twins (ETs) were activated to carry plastic strain. With increasing rolling passes, {101¯2} ET boundaries migrated toward the matrix region and absorbed a large number of dislocations, thereby reducing the dislocation density within deformed grains. This phenomenon would delay the DRX onset, resulting in a small DRX volume fraction of approximately 11.4%. The pronounced difference in the DRX behavior between bimodal non-basal texture sheets and basal texture sheets at medium temperature primarily accounts for their similar rolling performance, with mere 4.4% difference in accumulative thickness reduction.
High nitrogen austenitic stainless steels have emerged as crucial materials in the steel industry due to their excellent comprehensive properties and their cost-effective and ecofriendly characteristics. However, the yield strength of those alloys at room temperature is limited and fails to meet the requirements for high stress loads. Therefore, high nitrogen austenitic stainless steels having high strength and good ductility are urgently needed. This study focuses on a high nitrogen austenitic stainless steel with a nominal composition of Fe-18.87Cr-10.09Mn-1.12Ni-0.53N-0.18Si-0.04C (mass fraction, %). The steel plate was subjected to cryogenic rolling at the liquid nitrogen temperature with a thickness reduction of 10%, achieving exceptional comprehensive mechanical properties, including a yield strength of 947 MPa, a tensile strength of 1051 MPa, and a uniform elongation of 36%. These results are comparable to the optimal strength and ductility obtained by traditional thermomechanical processes including cold rolling and its subsequent annealing. The substantial enhancement in yield strength, which is 1.86 times than that of the homogenized state, is primarily attributed to the dense dislocation substructures and complex lamellar structures composed of ε-martensite laths, the deformation twins, and local chemical order lath structures introduced during the cryogenic rolling process. The structures induce a synergistic effect of multiple strengthening mechanisms. Moreover, the material maintains good uniform elongation and work hardening ability, which can be attributed to dislocation slip and the significant twinning-induced plasticity effect during plastic deformation. The cryogenic rolling technique demonstrated offers remarkable advantages in cost-savings, process simplification, and efficiency improvement in the preparation and production of the high nitrogen austenitic stainless steel.
The core issue in the study of giant magnetostriction of Fe-Ga alloy thin sheet is to obtain preferential texture through secondary recrystallization. In this work, the evolution of the texture, precipitation, and grain boundary characteristics of an Fe-Ga alloy thin sheet during the annealing process were investigated using XRD, SEM, EBSD, and TEM. The mechanism of the secondary recrystallization of the Goss ({110}<001>) texture in the Fe-Ga alloy thin sheet was analyzed. The results show that the primary recrystallized thin sheet is composed of strong γ-fibers and has a weak Goss texture. Moreover, high-density MnS and NbC precipitates of size 20-40 nm are dispersedly distributed in the matrix grains after primary recrystallization. The coarsening of the precipitates and a decrease in the volume fraction and density weaken the inhibiting force during the annealing process. The density of the precipitates inside the Goss grains is lower than that of the precipitates in the matrix grains with γ-texture during the process from primary recrystallization to secondary recrystallization. Before the occurrence of secondary recrystallization, Goss grains do not exhibit a number and size advantages over the matrix grains but are surrounded by higher-energy grain boundaries than the matrix grains. The differences between the Goss and matrix grains in terms of precipitation and high-energy grain boundary characteristics during primary recrystallization provide an additional driving force for the secondary recrystallization of Goss grains. Therefore, a perfect secondary recrystallization of the Goss texture with a saturation magnetostriction coefficient of 250 × 10‒6 is produced in the Fe-Ga alloy thin sheet without the introduction of the surface energy effect using a special annealing atmosphere.
The Mg-Al-Zn-Mn-Ca magnesium alloy, after hot rolling, forms an elliptical texture, providing good application prospects. However, challenges such as poor symmetry, similar to basal textures, persist in elliptical texture formation. This study explores optimizing the texture of Mg-2Al-02Zn-0.4Mn-0.5Ca Mg alloy sheets using a hot rolling-shearing-bending (HRSB) treatment to improve their room temperature mechanical properties. The research systematically investigates structural evolution during the annealing process and the mechanism behind nonbasal texture formation, using EBSD, XRD, and other characterization techniques. The results show that after annealing at temperatures above 350 oC following hot rolling, the sheets develop an elliptical texture extending toward the transverse direction (TD). Following HRSB treatment and annealing at 400 oC annealing, the {101¯2} extension twins generated during deformation remain uncrystallized, leading to an increase in the relatively symmetrical texture components between 20° and 70°. This also results in the formation of a ring texture. However, as the annealing temperature increases to 450 oC, the {101¯2} extension twins nearly disappear, precipitation phases increase, and the nucleation of randomly oriented grains during recrystallization causes the circular texture characteristics to disappear. During the HRSB deformation process, the pyramidal <c + a> slip becomes significantly activated, dominating the primary dislocation density. The low-energy grain boundaries caused by the co-segregation of Al and Ca atoms at the grain boundaries, as well as the orientation gradient induced by the non-basal slip, jointly contribute to the formation of the non-basal texture.
Slight variations in the Al content can considerably affect the solidification path of TiAl alloys. Consequently, these variations influence the location of phase regions during the hot deformation process of TiAl alloys. In this study, Ti-(43-45)Al-4Nb-1Mo-0.2B (TNM, atomic fraction, %) ingots were synthesized via arc melting and labeled as 43Al, 44Al, or 45Al depending on their Al contents. Subsequently, TNM sheets were fabricated via hot-pack rolling, and the influence of Al content on the microstructure evolution and mechanical properties of these sheets during the rolling process was systematically investigated.Results indicate that TNM alloys with different Al contents are located in different phase regions when deformed at 1250 oC. After preheating for 1 h, the 43Al alloy is mainly composed of equiaxed α/α2 grains. In contrast, the 44Al alloy exhibits a unique core-shell-like structure with α2/γ lamellar colonies in the core and α/α2 grains surrounding it. Compared with the 44Al alloy, the 45Al alloy demonstrates a lamellar structure with larger α2/γ lamellar colonies. Furthermore, the initial structure remarkably influences the microstructure evolution of TNM sheets during the rolling process and determines the final microstructure composition of these sheets. With increasing Al content, the microstructure of TNM sheets transitions from nearly lamellar to duplex, eventually tending toward a near-γ structure. Additionally, two types of α2/γ lamellar colonies—newly formed and initially present—are observed in the 43Al and 45Al sheets, respectively. Owing to its unique core-shell-like structure, the 44Al sheet simultaneously contains both types of α2/γ lamellar colonies. Furthermore, the mechanical properties of TNM sheets with different Al contents were tested at room temperature. Results show a gradual decrease in the tensile strength of TNM sheets with increasing Al content. The 43Al sheet exhibits the best performance, which is attributed to the presence of newly formed lamellar structures. Meanwhile, the 44Al and 45Al sheets develop fractures rapidly because of the increased, clustered, and abnormal growth of equiaxed γ grains or presence of residual α2/γ lamellar colonies.
Face-centered-cubic high-entropy alloys have attracted extensive attention due to their comprehensive mechanical and other properties. However, these alloys suffer from low yield strength, making it imperative to develop alloys with high yield and tensile strengths. This study systematically investigates the microstructural characteristics and tensile mechanical properties of the Fe50Mn29-Co10Cr10Cu1 high-entropy alloy processed by rolling at three temperatures (-196, 25, and 300 °C) followed by annealing. The aim is to elucidate the deformation mechanisms associated with different processing routes and their influences on strength and ductility. During uniaxial tensile deformation, deformation twins produced by liquid-nitrogen and room-temperature rolling along with lath-like reversed austenite impede dislocation slip, thereby improving the yield strength of the alloy. In contrast, the alloy processed by warm rolling and annealing shows few deformation twins, with dislocation slip and stacking faults dominating as the deformation mechanisms. The alloy processed by liquid-nitrogen rolling followed by 500 oC annealing exhibits high yield strength but poor plasticity. Conversely, alloys rolled at room temperature and 300 oC followed by 500 oC annealing demonstrate higher yield strengths and certain degree of work hardening capability, showing corresponding yield strengths of 752 and 604 MPa, tensile strengths of 917 and 784 MPa, and uniform elongations of 11.2% and 26.2%. The differing microstructures resulting from processing at varied temperatures and subsequent annealing lead to significant differences in mechanical behavior under tensile testing.
Cu/Al laminated composites combine the lightweight advantage of aluminum with the high electrical and thermal conductivity of copper, and are widely used in the new energy, communication, electric power, and related industries. Traditionally, cold rolling has been the primary method for producing these composites; however, it often results in poor interfacial bonding and promotes the formation of oxides at the interface. In contrast, the high-temperature oxygen-free rolling process can significantly improve composite preparation by enabling precise layer temperature control and creating an anaerobic environment. This process typically forms a mechanical bonding interface, necessitating subsequent annealing to achieve a metallurgical bond that enhances interfacial integrity and optimizes performance. Therefore, developing an annealing process that complements the rolling method is essential. Based on this context, a Cu/1060Al/Cu three-layer composite was fabricated using T2 copper and 1060 aluminum as base materials. The effects of rolling passes and annealing parameters on the mechanical properties and conductivity of the composite were investigated. In addition, the current density distribution within the composite was simulated using Ansys software. After annealing at 350 oC for 2 h, the interface layer of the Cu/1060Al/Cu composite became uniform and continuous, with microcracks in the rolled interface layer effectively eliminated. According to strength-plasticity product calculations, the composite exhibited optimal overall performance after two rolling passes, achieving a yield strength of 107 MPa, tensile strength of 178 MPa, and elongation of 67%. Under the combined influence of the interface layer and the constraining effect of the copper layers on both sides of the aluminum core, the composite displayed a collaborative tensile fracture mode. The measured conductivity of the Cu/1060Al/Cu composite reached 70.1%IACS satisfying the requirements for conductor applications. The current density distribution in the annealed Cu/1060Al/Cu composite primarily varied with current frequency, demonstrating the skin effect characteristics typical of alternating current. The current density decreased with increasing frequency and increased with a higher proportion of the copper layer. Notably, increasing the copper layer proportion does not always lead to better performance. It is necessary to comprehensively consider electrical conductivity and material usage when determining the copper layer proportion. An appropriate range for the single-sided copper layer proportion is 10.0%-17.5%.
Ti2AlNb alloys are a type of lightweight material that has excellent high-temperature performance exceeding that of titanium alloys. Manufacturers often use rolling as a major method to obtain a Ti2AlNb sheet. After rolling, the mechanical properties of the resulting Ti2AlNb sheets exhibit evident anisotropy, but the anisotropic mechanism remains unclear. In view of the anisotropic tensile properties of Ti2AlNb sheets, this study investigates the microstructure, texture, and tensile properties of Ti2AlNb sheets, as well as to explore the main factors affecting the anisotropy of sheet tensile properties. Results indicate that the microstructure of Ti2AlNb alloy sheets consists of α2, B2, and O phases, with each phase exhibiting a strong texture. The B2 phase forms a slightly rotated cubic texture, whereas the O phase develops a distinct <100>//ND (normal direction) phase transformation texture, which is related to the orientation of the α2 and B2 phases. The α2 phase exhibits a strong rolling thermal deformation-induced {112¯0}<uvtw> texture. The tensile properties of the sheets at room temperature (24 oC) and 650 oC exhibit remarkable anisotropy, with the transverse tensile strength being higher than the longitudinal strength. However, the longitudinal elongation is higher than the transverse elongation. This result is attributed to the near-T-type strong texture of the α2 phase and <100>//ND phase transformation texture of the O phase, which make the respective prismatic <a> slip more difficult to activate in the transverse direction of the sheets. As the tensile testing temperature increases to 700 oC, the activation of pyramidal <c + a> slip in the α2 and O phases markedly reduces the anisotropy of the tensile properties.
Recent advancements in grain boundary engineering have revealed that the {111}/{111} near singular boundary (NSB) exhibits superior resistance to corrosion attacks than the random boundary in aluminum and its alloys. Thus, understanding the influential factors and formation mechanisms of the {111}/{111} NSB, as well as regulating such boundaries, is crucial for enhancing the resistance performance of aluminum and its alloys against intergranular corrosion attacks. To intrinsically comprehend the formation mechanism of the {111}/{111} NSB in aluminum alloys, this study used high purity aluminum (99.99%) as the experimental material. Initially, the starting samples were synthesized through multidirectional forging at room temperature (25 oC), followed by recrystallization annealing at 370 oC. The as-synthesized starting samples exhibited uniform microstructures with an average grain size of 20 μm and random grain orientations. Subsequently, two parallel starting samples were rolled at 25 oC and at the cryogenic temperature (-196 oC), respectively, with an 80% thickness reduction, followed by immediate recrystallization annealing at 370 oC for 30 min. Later, a quantitative grain boundary inter-connection characterization method based on EBSD and five parameter analysis was employed to statistically analyze the grain boundary character distributions within the samples. The results revealed that the cryo-rolled and recrystallized sample featured a higher proportion of the {111}/{111} NSB compared to the 25 oC-rolled and recrystallized sample. Specifically, the {111}/{111} NSB fraction in the former reached 6.0%, 2.22 times that in the latter. XRD analysis, hardness testing, and EBSD measurements revealed the development of a strong {011}<111¯> deformation texture in the samples rolled at 25 oC or the cryogenic temperature. In particular, cryo-rolling was found to impede dynamic recovery; hence, the sample rolled at this temperature featured higher levels of residual compression stress, increased grain fragmentation, and higher stored energy compared to the sample rolled at 25 oC. Owing to the higher driving force and more active {011}<011¯>-oriented growth, the cryo-rolled sample formed larger grains and stronger {011}<011¯> recrystallization textures during the subsequent recrystallization annealing. Statistical analysis based on grain boundary tracing demonstrated that the grain boundaries between {011}<011¯>-oriented grains and other oriented grains contained higher proportions of the {111}/{111} NSB compared to the grain boundaries between two randomly oriented grains. Moreover, boundaries between the {011}<011¯>- oriented grains and their diffusive orientations featured notably high proportions of the {111}/{111} NSB. This explains the higher content of the {111}/{111} NSB observed in the cryo-rolled and recrystallized sample than that in the 25 oC-rolled and recrystallized sample.
Oil casing steel plays a critical role in the oil and natural gas industry, and its performance is significantly influenced by non-metallic inclusions. Rare earth (RE) elements can effectively modify these inclusions. In this study, industrial experiments were conducted to investigate the effects of rare earth metal alloying on inclusion characteristics during the refining, continuous casting, and hot-rolling processes. The evolution of inclusion morphology, quantity, and size was analyzed using SEM-EDS, FactSage 8.3 thermodynamic software, and an OTS One Bond inclusion analysis system. Results show that when the rare earth content was 4 × 10-6, the total oxygen content decreased to 7 × 10-6. In addition, rare earth microalloying transformed Ca-Al-O inclusions into Ca-RE-Al-O inclusions. Following alloying, the inclusion number density in continuous casting billet samples increased from 44 mm-2 to 46 mm-2, with the number density of 0-2 μm inclusions rising from 13 mm-2 to 18 mm-2, while the number density of 5-30 μm inclusions fell from 7 mm-2 to 5 mm-2. Overall, the average inclusion size decreased after rare earth metal addition. XRD and XRF analyses revealed the formation of rare earth phases in the refined slag after vacuum degassing rare earth alloying. Thermodynamic calculations indicate that at 1600 oC, the Gibbs formation energies of CaO and CeAlO3 in steel were -357088.82 and -86892.89 J/mol, respectively, supporting the formation of these inclusions upon rare earth addition. In RE-free furnaces, both thermodynamic calculations and experimental results showed that CaS inclusions formed during solidification, with CaS precipitating around the edges of Ca-Al-O/Ca-RE-Al-O inclusions. In RE-containing furnaces, the addition of rare earth reduced the precipitation of calcium aluminate inclusions, leading instead to the formation of CaO·REAlO3 inclusions, which likely serve as nucleation sites for CaS precipitation during solidification. During hot-rolling, long strip inclusions were observed in steel without rare earth; however, rare earth alloying improved the deformation ability of inclusions, preventing the formation of long strips due to inclusion crushing. Notably, the modifications induced by rare earth were independent of the inclusions’ Ca content. In hot rolled tube samples without rare earth, only inclusions with moderate Ca content exhibited good deformability. The low yield of rare earth metal was primarily attributed to reactions between the molten steel and refining slag, as well as the removal of rare earth inclusions from the molten steel to the slag.
Traditional austenitic stainless steel (ASS) faces challenges in operating safely under low-temperature sliding wear conditions because of its relatively low strength and hardness. To address this issue, this study focused on high-nitrogen 316LN ASSs. Through controlled rolling and annealing, three microstructures were designed: non-recrystallized, heterogeneous, and fully recrystallized microstructures (marked by NG, HS, and CG structures, respectively). The influence of environmental temperature and microstructure on the tribological behavior and wear mechanisms of high-nitrogen 316LN ASSs was investigated. The results demonstrate that the HS structure exhibits the lowest friction coefficient because the reduced number of abrasive particles limits the direct contact between the worn surface and the counterpart, outperforming the NG and CG structures. As the environmental temperature decreases, the wear rates of all the structures decrease, with the lowest wear rate observed at -120 oC. At this temperature, the CG structure exhibits the lowest wear rate—surpassing the NG and HS structures—attributed to its low stacking-fault energy, inducing martensitic transformation and forming a nano/submicron crystalline hardened layer. This layer effectively prevents crack propagation and enhances wear resistance. Although martensitic transformation and surface hardening also occur in the HS structure, the wear debris generated during sliding acts as a third-body abrasive, accelerating wear and degrading wear resistance. In contrast, the CG structure, which exhibits excellent low-temperature plastic deformation ability, shows only mild abrasion during the wear process.
Zirconium alloy sheets exhibit limited formability at room temperature, often leading to cracking during the fabrication of spacer grids in nuclear reactors. This study presents stamping experiments conducted on Zr-4 sheets, with microstructure and texture characteristics measured at various positions along the longitudinal section using EBSD. The in-grain misorientation axes method was employed to analyze deformation mode selection. Supported by finite element method simulations, a visco-plastic self-consistent model was applied to quantify the activation of deformation modes and elucidate the relationship between texture evolution and slip/twin activity. In addition, the effects of strain paths on crack formation mechanisms were investigated. The results indicate that cracking primarily occurred around the punch radius. Positions near the punch radius followed a plane strain path, whereas regions along the slope wall and die radius exhibited a uniaxial tension path. Prismatic <a> slip was found to dominate deformation across all loading strain paths. Near the die radius, pyramidal <c + a> slip and tensile twinning were activated to accommodate stamping deformation, resulting in the formation of new texture components aligned along the rolling direction. The increase in basal texture strength around the punch radius was attributed to basal <a> slip, serving as a secondary dominant slip system. Furthermore, prismatic slip, in coordination with basal slip, facilitated the texture transition from a double-peak structure to a basal texture.
