National Key Research and Development Program of China(2022YFE0110800) National Natural Science Foundation of China(52201011) National Natural Science Foundation of China(51922054)
Incorporating metastable austenite is the one of the key strategies for achieving synergistic improvement in the strength and ductility of high-strength steels. Through in situ deformation-induced martensitic transformation during tensile loading, metastable austenite can delay necking while enhancing work-hardening capacity. Concurrently, ultrahigh-strength steel components are facing increasing demands in terms of lightweightness and service in complex environments; hence, they will be required to have a higher fracture toughness without compromising strength. Research has focused on incorporating the tougher austenite phase in high-strength steels to improve their fracture toughness and preserve ductility. Metastable austenite contributes to enhanced fracture toughness through transformation toughening and its interactions with cracks, which can deflect or blunt cracks. However, freshly formed martensite, a product of martensitic transformation, can reduce the toughening effect or even deteriorate fracture toughness due to its inherent brittleness and effect on the local stress state. This paper reviews recent research progress on the relationship between metastable austenite and fracture toughness of high-strength steels, examining the toughening and embrittlement mechanisms of the phase. In addition, it outlines future design principles for metastable austenite incorporation in high-strength steels to achieve synergistic improvements in strength and toughness.
TANG Jingtao, YAO Yingjie, ZHANG Youyou, WU Wenhua, LI Yubo, CHEN Hao, YANG Zhigang. Research Progress on the Influence of Metastable Austenite on the Fracture Toughness of High-Strength Steels[J]. Acta Metallurgica Sinica, 2025, 61(1): 77-87 DOI:10.11900/0412.1961.2024.00142
Fig.2
Transformation zone schematics of energy adsorption theory (a) and crack tip shielding theory (b), crack propagation resistance curve predicted by transformation toughening theory (c), and the dependence of toughening behavior on the critical transformation stress (d) (h—semi-major axis of the elliptical transformation zone, βh—semi-minor axis of the elliptical transformation zone, r—distance between the edge of transformation zone and the crack tip, θ—angle between the line which originates from the crack tip connecting the transformation-zone edge, and the crack plane, ΔKI—increment of the stress intensity factor resulted by phase transformation, —critical value of ΔKI, Δa—crack length, —type I stress intensity factor, σM—critical stress for martensitic transformation)
Fig.3
Contour maps of strain triaxiality distributions exposed to different TRIP treatments and with varying carbon concentrations[57] (—through-thickness strain, I'—axis: horizontal distance from the crack tip, h'—vertical distance from the crack tip)
(b) martensite-martensite interfacial cracking[57] (c, d) martensite-matrix interfacial cracking[56,57] (Where orange arrows in Fig.4d point to martensite-matrix interface decohesion while green arrows show martensite cracking)
Fig.5
Changes of energy release rate () due to phase transformation, corresponding evaluated from energy adsorption theory, and the carbon concentration in retained austenite varying with quenching & partitioning process[77] (The sample axis represents the quenching & partitioning parameters, e.g. QP260(60) indicates partitioning at 260 oC for 60 min)
总体而言，目前面向高韧性的亚稳奥氏体成分和结构设计理论尚不清晰，其关键点在于阐明脆化效应与韧化效应之间的竞争关系。① 新鲜马氏体的脆化效应与裂纹偏转之间的竞争关系。虽然新鲜马氏体的板条块及板条束边界在裂纹扩展前端可以偏转裂纹，但新鲜马氏体与基体之间的界面较为薄弱[56]，当裂纹尖端扩展到较薄弱的界面时由于阻力较小而快速生长，导致整体的脆化效应。② 新鲜马氏体的脆化效应与裂纹钝化之间的竞争关系。当新鲜马氏体-基体界面较弱或特定晶面解理断裂倾向很大时，裂纹在钝化之前就会快速扩展。Wang和Huang[87]研究提出，如果新鲜马氏体的流变应力较低，则裂纹可以发生钝化；反之如果新鲜马氏体-基体之间的界面强度较低，则裂纹不发生钝化，将沿晶界处快速扩展，因此TRIP效应能否增韧取决于马氏体的流变应力与新鲜马氏体-基体之间的强度匹配度。③ 亚稳奥氏体的微观结构与裂纹偏转/钝化能力之间的关联。不同形貌、尺寸的奥氏体在相变时产生的应力状态差异较大，对裂纹的偏转/钝化能力也不尽相同。虽然目前普遍认为薄膜状亚稳奥氏体对裂纹的钝化能力更强，但尚缺乏系统的研究。在超高强度钢中，裂纹钝化能力是决定断裂韧性的重要因素之一。Handerhan和Garrison[88]在研究HP9-4-20二次硬化钢时，通过调控回火温度及时间得到可以将裂纹平滑钝化(即裂纹尖端为圆弧过渡)及顶点钝化(Blunting to vertices，裂纹尖端以方形或三角形过渡)的不同样品，在具有相同碳化物析出密度及间距的情况下，相较于平滑钝化的直接淬火态样品，顶点钝化的时效样品可以将临界裂纹尖端张开位移增加约一倍。
Ultra-high strength steels have been widely used in the critical engineering structures in both military and civilian applications due to the combination of ultra-high strength and excellent toughness. In this paper, firstly, the typical ultra-high strength steel grades that have been employed were introduced, and their compositions, mechanical properties, application and histories of development were summarized with the emphasis on their microstructures and strengthening/toughening mechanism; secondly, the latest progress on the emerging ultra-high strength steel grades was reviewed, including their compositions, microstructures, strengthening mechanism and mechanical properties; thirdly, the newly emerging demands on replacing the currently employed ultra-high strength steels in China were defined, including steels for low-density but ultra-strong armors, the large ball grinding mill, cutters of tunnel boring machine and high pressure fracturing pump; finally, recent research results on ultra-high strength and high-toughness medium Mn steel were presented, which overcame the trade-off of strength and toughness to a greater extent; on this basis, some suggestions were put forward for the future development of these steel grades to meet the urgent national demands.
Cellular microstructure is a unique feature in alloys fabricated by selective laser melting (SLM). Abundant efforts have been made to reveal the formation mechanism of cellular microstructures and its influences on mechanical performances, while its potential role in microstructure architecting during post-heat treatment is rarely explored. In this work, we investigated the features of cellular microstructures in an SLM-fabricated 18Ni(300) steel and revealed how this microstructure influences austenite reversion upon aging. Segregation of Ti and Mo is experimentally detected at cell boundaries. It is interestingly found that a distinctive reverted austenite network forms rapidly along cell boundaries during aging, whereas much less austenite is found in conventionally treated 18Ni(300) steels. The rapid austenite reversion in SLM-fabricated material proceeds mainly via the growth of retained austenite on cell boundaries while the nucleation and growth of new austenite grains is negligible. Phase-field simulations suggest austenite grows in a fast, partitionless manner along cell boundaries where the chemical driving force for austenite reversion is substantially enhanced by Ti and Mo segregations, but in a sluggish, partitioning manner towards cell interiors. Contrary to conventional views that austenite fraction should be confined to avoid strength reduction, current SLM-fabricated 18Ni(300) steel containing ∼13% cellular austenite is found to have higher tensile strength compared to its counterparts with negligible austenite. The design of austenite also shows its potential to enhance fracture toughness. The current study demonstrates that cellular structures could substantially alter austenite reversion behavior, providing a new route for microstructure architecting in additively manufactured steels.
WangB, NiuM C, WangW, et al.
Microstructure and strength-toughness of a Cu-contained maraging stainless steel
An increase in strength often leads to a decrease in the ductility and toughness of maraging stainless steels; this phenomenon is known as the strength-ductility/toughness trade-off dilemma in structural materials. Some studies have found that the introduction of submicro/nanometer-sized retained or reverted austenite could mitigate the strength-ductility/toughness trade-off of high-strength maraging stainless steels. In this work, a novel strategy to accelerate austenite reversion by Cu addition in a Fe-Ni-Mo-Co-Cr maraging stainless steel was studied. In addition, the aging behavior and its effects on the mechanical properties of a Cu-containing Fe-Cr-Co-Ni-Mo maraging stainless steel were systematically studied. Transmission electron microscope characterizations showed that Cu- and Mo-rich phases precipitated from the steel matrix in sequence during the aging process; more specifically, a part of Mo-rich phase nucleated at the Cu-rich phase and then grew. Moreover, along with the segregation of Cu and Ni, reverted austenite was formed gradually. With an increase in the aging time, the stability of the reverted austenite increased, resulting in a substantial increase in its toughness. After aging for 90 h, the yield and tensile strengths of the steel reached 1270 and 1495 MPa, respectively, and the impact energy and fracture toughness were 81 J and 102 MPa·m1/2, respectively, showing an excellent match of strength and toughness compared with commercial maraging stainless steels.
Quantitative evaluation of the contribution of carbide-free bainite, lath martensite, and retained austenite on the mechanical properties of C-Mn-Si high-strength steels
Owing to the excellent combination of specific strength and ductility, medium Mn steels (MMSs) with Mn contents of 3%-12% (mass fraction) are considered the most promising candidates for the third-generation advanced high-strength steel. The combination of excellent strength-ductility is mainly attributed to the active transformation-induced plasticity effect of the metastable retained austenite during deformation. Therefore, producing a considerable amount of retained austenite with reasonable stabilities in the steel by various heat treatment schedules is always important. In this study, granular- and lamellar-structured retained austenites were developed in a cold-rolled 0.15C-5Mn MMS by introducing a technical process of precontrolling ferrite recrystallization in the annealing schedule. The microstructures of the annealed samples were analyzed using SEM, EBSD, and TEM. The results show that duplex microstructures comprising various amounts of recrystallized ferrite and fresh martensite can be obtained in the cold-rolled MMS when controlling the occurrence of recrystallization at different intercritical temperatures by a preannealing process. When this microstructure is used for the final austenite reverted transformation annealing, the resultant ultrafine duplex microstructure with recrystallized ferrite and two types of heterogeneous retained austenite, i.e., lamellar and granular, is produced. The heterogeneous-structured austenite shows more sensitivity to increasing strain, i.e., various mechanical stabilities, which enable an excellent strength-ductility combination and reduced Lüders strain in the cold-rolled medium Mn steel.
Recently, medium-Mn steel, used in the automotive industry, has attracted increasing attention as the one of the most promising candidates for the third generation of advanced high strength steels owing to its reasonable cost and excellent mechanical properties. In this study, the effect of intercritical annealing temperature on the microstructure and mechanical properties of a new composition steel was investigated, and its strengthening mechanism and related reasons were analyzed. In addition, a ultra-high product of strength and plasticity (> 70 GPa·%) of hot rolled medium manganese steel with a segregation band was eventually obtained. The results show that the grain size and orientation in the packet (defined by the original austenite grain boundary) significantly affect the mechanical properties and deformation microstructure of the material obtained under different temperatures. The obvious precipitation and dissolution processes of carbides occur at higher temperatures, and thus influence the mechanical stability of reversed austenite. During the tensile process, because it is easier to deform, the favorable packets in the non-segregation zone form an elongated-strip fine-grain zone along the loading direction, while the unfavorable packets form fragmentary grain regions. Moreover, martensite transformation preferentially occurs at the obvious orientation inside the austenite grain and the boundaries where large strain is accumulated. Through coordinated deformation, the adjacent packets eventually tend to form alternate distribution of the two kinds of micro-zone substructures, which is accompanied by the significant evolution of low-angle grain boundaries related to the dislocation activity. Due to the wide distribution of grain size in one packet, the reversed austenite in the non-segregation zone can withstand large deformation, which makes the austenite in the segregation zone undergo sufficient strain-induced martensitic transformation (SIMT), to obtain excellent combination of strength and toughness.
Twinning-induced plasticity (TWIP) steel has received significant research attention because of its superior mechanical properties, including uniform elongation, ultimate tensile strength, and fracture toughness. However, it has a relatively low yield stress, which limits its industrial application. Increasing the dislocation density has been proved to be an effective method for enhancing the yield stress. In this work, a simple warm rolling (WR) route was applied at 700oC to manufacture partially recrystallized TWIP steel with a high yield stress (1250 MPa), good total elongation (24%), and exceptional fracture toughness (KJIC of approximately 125 MPa·m1/2). The steel manufactured using WR was characterized using SEM, EBSD, and TEM at different length scales. Compared to the steel microstructure obtained after hot rolling or cold rolling (CR), this WR TWIP steel exhibits a distinct heterogeneous structure. The matrix has numerous dislocations with twinned coarse grains (approximately 75%) and nearly defect-free recrystallized fine grains (approximately 25%), which form during the reheating period of the WR process. The in situ tensile tests of the WR and CR steels show that the deformed coarse grains provide high yield stress with negligible deformation, whereas the recrystallized fine grains can undergo considerable plastic deformation, which results in a good work hardening capacity during tensile deformation. The fracture toughness tests of the compact tension (C(T)) samples indicate that the recrystallized grains in the WR steel can enhance the crack tip blunting and deflect cracks, which enhance the crack-growth resistance. Alternatively, these toughening mechanisms are not observed in the homogeneous CR steel. Therefore, this heterogeneous structure, which is induced by the high temperature WR process, provides the TWIP steel with excellent strength and toughness.
Role of microstructural characteristics in combination of strength and fracture toughness of laser additively manufactured ultrahigh-strength AerMet100 steel
A comparison of the fracture behavior of two heats of the secondary hardening steel AF1410
[J]. Metall. Trans., 1989, 20A: 105
DelagnesD, Pettinari-SturmelF, MathonM H, et al.
Cementite-free martensitic steels: A new route to develop high strength/high toughness grades by modifying the conventional precipitation sequence during tempering
[J]. Acta Mater., 2012, 60: 5877
MondiereA, DéneuxV, BinotN, et al.
Controlling the MC and M2C carbide precipitation in Ferrium® M54® steel to achieve optimum ultimate tensile strength/fracture toughness balance
[J]. Mater. Charact., 2018, 140: 103
LiuZ B, YangZ, WangX H, et al.
Enhanced strength-ductility synergy in a new 2.2 GPa grade ultra-high strength stainless steel with balanced fracture toughness: Elucidating the role of duplex aging treatment
The development of strong, tough, and damage-tolerant ceramics requires nano/microstructure design to utilize toughening mechanisms operating at different length scales. The toughening mechanisms so far known are effective in micro-scale, then, they require the crack extension of more than a few micrometers to increase the fracture resistance. Here, we developed a micro-mechanical test method using micro-cantilever beam specimens to determine the very early part of resistance-curve of nanocrystalline SiO2 stishovite, which exhibited fracture-induced amorphization. We revealed that this novel toughening mechanism was effective even at length scale of nanometer due to narrow transformation zone width of a few tens of nanometers and large dilatational strain (from 60 to 95%) associated with the transition of crystal to amorphous state. This testing method will be a powerful tool to search for toughening mechanisms that may operate at nanoscale for attaining both reliability and strength of structural materials.
AntolovichS D, SinghB.
On the toughness increment associated with the austenite to martensite phase transformation in TRIP steels
The effects of retained austenite on the crack propagation behavior of a submicron-structured bainitic steel under impact fracture were studied. Scanning electron micro-scopy (SEM), transmission electron microscopy (TEM), and electron back-scattering diffraction (EBSD) were employed to characterize the size, distribution, and quantity of the matrix structure, and the microstructure of the impact fracture samples under con-ditions of two different bainitic processes. The retained austenite content at 280 degrees C was higher than that at 320 degrees C, and the microstructure appeared more uniform and refined, resulting in better impact toughness. The martensite + retained austenite constituents took part in the initiation of the fracture process and the crack ended at film of retained austenite. During fracture, a mixture of brittle, hard block martensite + retained austenite was easy to induced a crack opening. The effect of the transformation-induced plasticity of the retained austenite with a small block and film can effectively cause passivity and even inhibit crack growth. (c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
ZouY, XuY B, HuZ P, et al.
Austenite stability and its effect on the toughness of a high strength ultra-low carbon medium manganese steel plate
Optimising the strength-ductility-toughness combination in ultra-high strength quenching and partitioning steels by tailoring martensite matrix and retained austenite
Quantitative evaluation of the contribution of carbide-free bainite, lath martensite, and retained austenite on the mechanical properties of C-Mn-Si high-strength steels
Role of microstructural characteristics in combination of strength and fracture toughness of laser additively manufactured ultrahigh-strength AerMet100 steel
A comparison of the fracture behavior of two heats of the secondary hardening steel AF1410
0
1989
Cementite-free martensitic steels: A new route to develop high strength/high toughness grades by modifying the conventional precipitation sequence during tempering
0
2012
Controlling the MC and M2C carbide precipitation in Ferrium? M54? steel to achieve optimum ultimate tensile strength/fracture toughness balance
0
2018
Enhanced strength-ductility synergy in a new 2.2 GPa grade ultra-high strength stainless steel with balanced fracture toughness: Elucidating the role of duplex aging treatment
... [56,57]Cracking as a consequence of the fresh martensite produced by retained austenite phase transformation
(a) martensite cleavage[57] ...
... (b) martensite-martensite interfacial cracking[57] (c, d) martensite-matrix interfacial cracking[56,57] (Where orange arrows in Fig.4d point to martensite-matrix interface decohesion while green arrows show martensite cracking) ...
... 总体而言，目前面向高韧性的亚稳奥氏体成分和结构设计理论尚不清晰，其关键点在于阐明脆化效应与韧化效应之间的竞争关系.① 新鲜马氏体的脆化效应与裂纹偏转之间的竞争关系.虽然新鲜马氏体的板条块及板条束边界在裂纹扩展前端可以偏转裂纹，但新鲜马氏体与基体之间的界面较为薄弱[56]，当裂纹尖端扩展到较薄弱的界面时由于阻力较小而快速生长，导致整体的脆化效应.② 新鲜马氏体的脆化效应与裂纹钝化之间的竞争关系.当新鲜马氏体-基体界面较弱或特定晶面解理断裂倾向很大时，裂纹在钝化之前就会快速扩展.Wang和Huang[87]研究提出，如果新鲜马氏体的流变应力较低，则裂纹可以发生钝化；反之如果新鲜马氏体-基体之间的界面强度较低，则裂纹不发生钝化，将沿晶界处快速扩展，因此TRIP效应能否增韧取决于马氏体的流变应力与新鲜马氏体-基体之间的强度匹配度.③ 亚稳奥氏体的微观结构与裂纹偏转/钝化能力之间的关联.不同形貌、尺寸的奥氏体在相变时产生的应力状态差异较大，对裂纹的偏转/钝化能力也不尽相同.虽然目前普遍认为薄膜状亚稳奥氏体对裂纹的钝化能力更强，但尚缺乏系统的研究.在超高强度钢中，裂纹钝化能力是决定断裂韧性的重要因素之一.Handerhan和Garrison[88]在研究HP9-4-20二次硬化钢时，通过调控回火温度及时间得到可以将裂纹平滑钝化(即裂纹尖端为圆弧过渡)及顶点钝化(Blunting to vertices，裂纹尖端以方形或三角形过渡)的不同样品，在具有相同碳化物析出密度及间距的情况下，相较于平滑钝化的直接淬火态样品，顶点钝化的时效样品可以将临界裂纹尖端张开位移增加约一倍. ...
The fracture toughness of TRIP-assisted multiphase steels
... [57]Contour maps of strain triaxiality distributions exposed to different TRIP treatments and with varying carbon concentrations<sup>[<xref ref-type="bibr" rid="R57">57</xref>]</sup> (<span class="formulaText"><inline-formula><math id="M24"><mfenced close="|" open="|" separators="|"><mrow><msubsup><mrow><mi>ε</mi></mrow><mrow><mn mathvariant="normal">33</mn></mrow><mrow><mi mathvariant="normal">c</mi><mi mathvariant="normal">t</mi></mrow></msubsup></mrow></mfenced></math></span></inline-formula></span><i>—</i>through-thickness strain, <i>I'—</i>axis: horizontal distance from the crack tip, <i>h'—</i>vertical distance from the crack tip)Fig.3
... ,57]Cracking as a consequence of the fresh martensite produced by retained austenite phase transformation
(a) martensite cleavage[57] ...
... (a) martensite cleavage[57] ...
... (b) martensite-martensite interfacial cracking[57] (c, d) martensite-matrix interfacial cracking[56,57] (Where orange arrows in Fig.4d point to martensite-matrix interface decohesion while green arrows show martensite cracking) ...
... ,57] (Where orange arrows in Fig.4d point to martensite-matrix interface decohesion while green arrows show martensite cracking) ...
... [77]Changes of energy release rate (<span class="formulaText"><inline-formula><math id="M28"><msubsup><mrow><mi>G</mi></mrow><mrow><mi mathvariant="normal">I</mi><mi mathvariant="normal">C</mi></mrow><mrow><mi>γ</mi></mrow></msubsup></math></span></inline-formula></span><span class="formulaNumber">)</span> due to phase transformation, corresponding evaluated <span class="formulaText"><inline-formula><math id="M29"><msubsup><mrow><mi>G</mi></mrow><mrow><mi mathvariant="normal">I</mi><mi mathvariant="normal">C</mi></mrow><mrow><mi>γ</mi></mrow></msubsup></math></span></inline-formula></span> from energy adsorption theory, and the carbon concentration in retained austenite varying with quenching & partitioning process<sup>[<xref ref-type="bibr" rid="R77">77</xref>]</sup> (The sample axis represents the quenching & partitioning parameters, <i>e.g.</i> QP260(60) indicates partitioning at 260 <sup>o</sup>C for 60 min)Fig.5
总体而言，目前面向高韧性的亚稳奥氏体成分和结构设计理论尚不清晰，其关键点在于阐明脆化效应与韧化效应之间的竞争关系.① 新鲜马氏体的脆化效应与裂纹偏转之间的竞争关系.虽然新鲜马氏体的板条块及板条束边界在裂纹扩展前端可以偏转裂纹，但新鲜马氏体与基体之间的界面较为薄弱[56]，当裂纹尖端扩展到较薄弱的界面时由于阻力较小而快速生长，导致整体的脆化效应.② 新鲜马氏体的脆化效应与裂纹钝化之间的竞争关系.当新鲜马氏体-基体界面较弱或特定晶面解理断裂倾向很大时，裂纹在钝化之前就会快速扩展.Wang和Huang[87]研究提出，如果新鲜马氏体的流变应力较低，则裂纹可以发生钝化；反之如果新鲜马氏体-基体之间的界面强度较低，则裂纹不发生钝化，将沿晶界处快速扩展，因此TRIP效应能否增韧取决于马氏体的流变应力与新鲜马氏体-基体之间的强度匹配度.③ 亚稳奥氏体的微观结构与裂纹偏转/钝化能力之间的关联.不同形貌、尺寸的奥氏体在相变时产生的应力状态差异较大，对裂纹的偏转/钝化能力也不尽相同.虽然目前普遍认为薄膜状亚稳奥氏体对裂纹的钝化能力更强，但尚缺乏系统的研究.在超高强度钢中，裂纹钝化能力是决定断裂韧性的重要因素之一.Handerhan和Garrison[88]在研究HP9-4-20二次硬化钢时，通过调控回火温度及时间得到可以将裂纹平滑钝化(即裂纹尖端为圆弧过渡)及顶点钝化(Blunting to vertices，裂纹尖端以方形或三角形过渡)的不同样品，在具有相同碳化物析出密度及间距的情况下，相较于平滑钝化的直接淬火态样品，顶点钝化的时效样品可以将临界裂纹尖端张开位移增加约一倍. ...
... [77] (The sample axis represents the quenching & partitioning parameters, e.g. QP260(60) indicates partitioning at 260 oC for 60 min)Fig.5
总体而言，目前面向高韧性的亚稳奥氏体成分和结构设计理论尚不清晰，其关键点在于阐明脆化效应与韧化效应之间的竞争关系.① 新鲜马氏体的脆化效应与裂纹偏转之间的竞争关系.虽然新鲜马氏体的板条块及板条束边界在裂纹扩展前端可以偏转裂纹，但新鲜马氏体与基体之间的界面较为薄弱[56]，当裂纹尖端扩展到较薄弱的界面时由于阻力较小而快速生长，导致整体的脆化效应.② 新鲜马氏体的脆化效应与裂纹钝化之间的竞争关系.当新鲜马氏体-基体界面较弱或特定晶面解理断裂倾向很大时，裂纹在钝化之前就会快速扩展.Wang和Huang[87]研究提出，如果新鲜马氏体的流变应力较低，则裂纹可以发生钝化；反之如果新鲜马氏体-基体之间的界面强度较低，则裂纹不发生钝化，将沿晶界处快速扩展，因此TRIP效应能否增韧取决于马氏体的流变应力与新鲜马氏体-基体之间的强度匹配度.③ 亚稳奥氏体的微观结构与裂纹偏转/钝化能力之间的关联.不同形貌、尺寸的奥氏体在相变时产生的应力状态差异较大，对裂纹的偏转/钝化能力也不尽相同.虽然目前普遍认为薄膜状亚稳奥氏体对裂纹的钝化能力更强，但尚缺乏系统的研究.在超高强度钢中，裂纹钝化能力是决定断裂韧性的重要因素之一.Handerhan和Garrison[88]在研究HP9-4-20二次硬化钢时，通过调控回火温度及时间得到可以将裂纹平滑钝化(即裂纹尖端为圆弧过渡)及顶点钝化(Blunting to vertices，裂纹尖端以方形或三角形过渡)的不同样品，在具有相同碳化物析出密度及间距的情况下，相较于平滑钝化的直接淬火态样品，顶点钝化的时效样品可以将临界裂纹尖端张开位移增加约一倍. ...
Effect of retained austenite on impact toughness and fracture behavior of medium carbon submicron-structured bainitic steel
0
2021
Austenite stability and its effect on the toughness of a high strength ultra-low carbon medium manganese steel plate
Optimising the strength-ductility-toughness combination in ultra-high strength quenching and partitioning steels by tailoring martensite matrix and retained austenite
1
2020
... 总体而言，目前面向高韧性的亚稳奥氏体成分和结构设计理论尚不清晰，其关键点在于阐明脆化效应与韧化效应之间的竞争关系.① 新鲜马氏体的脆化效应与裂纹偏转之间的竞争关系.虽然新鲜马氏体的板条块及板条束边界在裂纹扩展前端可以偏转裂纹，但新鲜马氏体与基体之间的界面较为薄弱[56]，当裂纹尖端扩展到较薄弱的界面时由于阻力较小而快速生长，导致整体的脆化效应.② 新鲜马氏体的脆化效应与裂纹钝化之间的竞争关系.当新鲜马氏体-基体界面较弱或特定晶面解理断裂倾向很大时，裂纹在钝化之前就会快速扩展.Wang和Huang[87]研究提出，如果新鲜马氏体的流变应力较低，则裂纹可以发生钝化；反之如果新鲜马氏体-基体之间的界面强度较低，则裂纹不发生钝化，将沿晶界处快速扩展，因此TRIP效应能否增韧取决于马氏体的流变应力与新鲜马氏体-基体之间的强度匹配度.③ 亚稳奥氏体的微观结构与裂纹偏转/钝化能力之间的关联.不同形貌、尺寸的奥氏体在相变时产生的应力状态差异较大，对裂纹的偏转/钝化能力也不尽相同.虽然目前普遍认为薄膜状亚稳奥氏体对裂纹的钝化能力更强，但尚缺乏系统的研究.在超高强度钢中，裂纹钝化能力是决定断裂韧性的重要因素之一.Handerhan和Garrison[88]在研究HP9-4-20二次硬化钢时，通过调控回火温度及时间得到可以将裂纹平滑钝化(即裂纹尖端为圆弧过渡)及顶点钝化(Blunting to vertices，裂纹尖端以方形或三角形过渡)的不同样品，在具有相同碳化物析出密度及间距的情况下，相较于平滑钝化的直接淬火态样品，顶点钝化的时效样品可以将临界裂纹尖端张开位移增加约一倍. ...
A study of crack tip blunting and the influence of blunting behavior on the fracture toughness of ultra high strength steels
1
1992
... 总体而言，目前面向高韧性的亚稳奥氏体成分和结构设计理论尚不清晰，其关键点在于阐明脆化效应与韧化效应之间的竞争关系.① 新鲜马氏体的脆化效应与裂纹偏转之间的竞争关系.虽然新鲜马氏体的板条块及板条束边界在裂纹扩展前端可以偏转裂纹，但新鲜马氏体与基体之间的界面较为薄弱[56]，当裂纹尖端扩展到较薄弱的界面时由于阻力较小而快速生长，导致整体的脆化效应.② 新鲜马氏体的脆化效应与裂纹钝化之间的竞争关系.当新鲜马氏体-基体界面较弱或特定晶面解理断裂倾向很大时，裂纹在钝化之前就会快速扩展.Wang和Huang[87]研究提出，如果新鲜马氏体的流变应力较低，则裂纹可以发生钝化；反之如果新鲜马氏体-基体之间的界面强度较低，则裂纹不发生钝化，将沿晶界处快速扩展，因此TRIP效应能否增韧取决于马氏体的流变应力与新鲜马氏体-基体之间的强度匹配度.③ 亚稳奥氏体的微观结构与裂纹偏转/钝化能力之间的关联.不同形貌、尺寸的奥氏体在相变时产生的应力状态差异较大，对裂纹的偏转/钝化能力也不尽相同.虽然目前普遍认为薄膜状亚稳奥氏体对裂纹的钝化能力更强，但尚缺乏系统的研究.在超高强度钢中，裂纹钝化能力是决定断裂韧性的重要因素之一.Handerhan和Garrison[88]在研究HP9-4-20二次硬化钢时，通过调控回火温度及时间得到可以将裂纹平滑钝化(即裂纹尖端为圆弧过渡)及顶点钝化(Blunting to vertices，裂纹尖端以方形或三角形过渡)的不同样品，在具有相同碳化物析出密度及间距的情况下，相较于平滑钝化的直接淬火态样品，顶点钝化的时效样品可以将临界裂纹尖端张开位移增加约一倍. ...
A quantitative connection between shear band mediated plasticity and fracture initiation toughness of metallic glasses
图1
