Micron-sized cantilever beams of a 304 stainless steel were fabricated by focused-ion-beam (FIB). The static bending and dynamic bending tests of the microbeams were carried out. The results show that with decreasing the beam thickness, the yield strength of the microbeam increases and the ductility decreases. The relation between the yield strength of the microbeam and beam thickness is similar to the Hall-Petch relation of the grain size strengthening. The increase in the yield strength of the thinner microbeam is attributed to the increase in the strain gradient contribution due to inhomogeneous deformation of the small dimensional material. The decrease in the ductility of the microbeam is attributed to fewer mobile dislocations in the grain. The threshold of the fatigue crack initiation from the notch of the microbeam is close to that of the bulk material.

The effect of hydrogen on nanoindentation creep of type 316 stainless steel has been investigated by nanoindentation techniques. The results showed that the crept saturation displacement increased twice After outgassing at room temperature for 200 h, the creep curves are basically identical with that before charging. This indicates the creep is caused by diffused hydrogen.

Taking nanocrystalline Nd2Fe14B as a typical sample, the effects of grain-size distribution on the anisotropy and coercivity in nanocrystalline hard magnetic materials have been investigated. The calculating results reveal that the effective anisotropy and coercivity of material decrease with the reduction of grain size, and rapidly decrease while the grain size is less than 20nm. The non-ideal distribution of grain size does not change the variation trendency of the effective anisotropy and coercivity with reducing grain size, however, promotes the decrease rate of effective anisotropy and coercivity. When the microstructure factor, pc, is 0.7, our calculated results agree basically with the experimental results. The decrement of coercivity is mainly due to the reduction of effective anisotropy for nanocrystalline Nd2Fe14B permanent magnetic material. nanocrystalline Nd2Fe14B hard magnet; effective anisotropy ; coercivity ; grain-size distribution

The effects of temperature, strain rate and plastic strain on flow behavior and microstructures of GH4586 wrought superalloy were investigated by compressive deformation performed on MTS machine at deformation temperatures of 950 to 1150℃ and strain rates of 0.001 to 1 s-1. The results show that the flow stress increases drastically with the decrease of deformation temperature and the increase of strain rate. Dynamic recrystallization process can be effectively promoted by increasing deformation temperature. When deformation temperature is higher than 1100℃, completely recrystallized microstructures can be obtained with engineering strain of 30%, while when the temperature is lower than 1050℃, dynamic recrystallization does not occur with engineering strain up to 40\%. Grain size of annealed microstructures increases with the increase of deformation temperature. Ideal plasticity and resultant microstructures can be achieved by effective control of deformation temperature.

Low cycle fatigue (LCF) behaviors of cast nickel-base superalloy K52 at different temperatures were investigated, and the fatigue parameters were given by analyzing its cyclic stress-strain curves and strain-life curves. Cyclic stress response curves show that the alloy exhibited cyclic hardening and softening behaviors at room temperature and 900℃, respectively. OM and SEM observations indicated that LCF cracks initiated predominantly on the surface of specimen or at the near-surface defects. Once initiated, cracks would propagate perpendicularly to the loading direction and the specimens exhibited transgranular fracture.

An optimization method was established to predict phase compositions and amounts in two--phase nickel base superalloys. Based on the compositions of alloys and their r phase, r phase compositions and r phase amounts were calculated with the use of the layered multi objective optimization algorithmic approach with tolerance. The optimization process was realized by establishing two relating objective functions and the corresponding constrained conditions. The results verified the feasibility and the accuracy of the present method.

The effect of adding small amounts of Ag to β-NiAl on surface morphology of alumina scale during the oxidation at 1000-1100oC and the oxidation kinetics of β-NiAl and NiAl-1Ag were investigated by TGA and SEM/EDS. The kinetics of β-NiAl presents two parabolic stages controlled by the growth of metastable alumina and stable α-Al2O3, respectively, while those of NiAl-1Ag are composed of three different parabolic stages controlled by the growth of γ-Al2O3, θ-Al2O3 and α-Al2O3, respectively. The additions of small amounts of Ag to β-NiAl favors the phase transformation from metastable alumina to α-Al2O3, while this effect disappears for an Ag content above 5% at 1000oC. Finally, the addition of 0.5% Ag to β-NiAl does not affect the surface morphology of Al2O3 at 1100oC.

By means of the measurement of the creep curve and the observation of TEM, an investigation has been made into the deformation feature and microstructure evolution of AZ31 Mg--alloy in the initial creep at elevated temperature. The results show that the deformation feature during creep produced in the primary stage is that a great deal of $\langle a\rangle$ dislocation is activated on basal and non--basal planes, and $\langle a+c\rangle$ dislocation slips on pyramidal planes. $\langle a\rangle$ dislocation generated during creep may cross--slip from one of non--basal plane to another non--basal planes. As creep goes on, the dynamic recovery (DRV) may occur, and the dislocations are concentrated to form the dislocation cells or walls. Another feature observed during creep is that twinning occurs as an important deformation mechanism, leading to improvement of the alloy ductility.

Fatigue life, surface deformation morphology, fatigue cracking and fatigue fractography of Al-0.7%Cu (mass fraction) alloy, produced by equal channel angular pressing (ECAP) for 4 passes, were investigated under constant stress or plastic strain control. It is shown that the specimens displayed obvious cyclic softening, which caused some difference in fatigue life at low or high stress range under constant stress and strain conditions. The plastic strain is carried either by shear bands only, or by shear bands and deformation bands, in the specimens fatigued under strain control. Consequently, fatigue cracks nucleated either along shear bands or along deformation bands. However, the plastic strain only localized in the shear bands of the specimens under stress control, as a result, leading to shearing fatigue cracking. The fatigue fractography consists of several different zones, including fatigue crack initiation, slow, fast propagation and final fracture.

Water cooled treatment after isothermal relaxation of deformed austenite in a Nb--bearing microalloyed steel always induced a bainite ferrite dominated microstructure. Most of strain induced precipitates distribute along dislocations and pin dislocations in sample relaxed for proper time. When these samples were reheated and held at 650 or 700℃, the non--equilibrium microstructures tend to evolve into equilibrium ones. The sample relaxed for 60 s displays the highest thermostability, while the microstructure evolution is the quickest in the sample relaxed for 1000 s even though it is the softest before reheating. Pre--strain before reheating accelerates the evolution process. The evolution of microstructures during reheating and holding consisted of polygonization, small angle boundary between laths disappearing and recrystallization induced polygonal ferrite. Hardness measurement showed two peaks in hardness--time curve of each relaxed sample. These results indicated that thermostability of microstructures are mainly determined by their formation history.

The microstructure and toughness of the coarse--grained heat--affected zone (CGHAZ) in laser welding of RPC (relaxation--precipitation controlling transformation) steel were investigated by thermal simulation with a Gleeble-1500 thermal simulator. The influence of the time cooled from 800-500℃, t8/5(0.3-30 s), on the microstructure of CGHAZ and the low temperature toughness were discussed. The experimental results indicate that the granular bainite is the dominate microstructure of the CGHAZ in laser welding of RPC steel, and the impact energy of the CGHAZ is much higher than that of base metal when t8/5 is between 3 s and 8 s. Considering the effect of the size, volume, number and shape of the M-A constituent on the toughness, a toughness factor of the M-A constituent is defined. As the toughness factor increases, the toughness of the granular bainite increases. The varied trend of the impact toughness with t8/5 is mainly determined by the toughness factor of the M-A constituent.

The microstructure and toughness of the coarse--grained heat-affected zone (CGHAZ) in laser welding of RPC (relaxation--precipitation controlling transformation) steel were investigated by thermal simulation with a Gleeble-1500 thermal simulator. The influence of the time cooled from 800-500℃, t8/5 (0.3-30 s), on the microstructure of CGHAZ and the low temperature toughness were discussed. The experimental results indicate that the granular bainite is the dominate microstructure of the CGHAZ in laser welding of RPC steel, and the impact energy of the CGHAZ is much higher than that of base metal when t8/5 is between 3 s and 8 s. Considering the effect of the size, volume, number and shape of the M-A constituent on the toughness, a toughness factor of the M-A constituent is defined. As the toughness factor increases, the toughness of the granular bainite increases. The varied trend of the impact toughness with t8/5 is mainly determined by the toughness factor of the M-A constituent.

Based on the effect of accelerating cooling on the microstructure and properties of thermo--mechanical control process (TMCP) steel, we proposed to adopt this method for improvement of heat affect zone (HAZ) toughness of X70 pipeline steel. The results of simulated experiment and actual weldment indicate that at appropriate accelerating cooling rate the M--A constituent in HAZ is reduced obviously in amount and replaced by tough austenite films. Coarse bainitic sheaves were obtained when jetting water directly to the sample and the toughness is not improved. Accelerating cooling with appropriate cooling rate is a simple and efficient method to improve the HAZ toughness.

Fine powders of the Cu-Fe alloy were manufactured by using the high-pressure gas atomization technique. The study of the powder microstructures indicated that the size and concentration of the atomized-droplets play important roles in the microstructure evolution. A smaller atomized-droplet has a finer dispersed microstructure. Alloys with composition close to the critical composition of the alloy system are relatively easy to be undercooled into the miscibility gap. The formation of Fe--poor layer on the surface of powder is mainly caused by two reasons. One is the Fe-rich droplets' Marangoni migration towards the center of the atomized-droplet due to the radial temperature gradient, and the other is the repulsive effect of the advancing solid-liquid interface on the Fe-rich droplets.

Directionally solidified microstructures of Cu-70%Sn peritectic alloy have been investigated by means of the directional solidification technique. The results show that the solidified microstructure consists of primary , peritectic  and the eutectic phase (+Sn), which is different from the equilibrium microstructure consisting of  phase and eutectic phase. The theoretical analysis results indicate that  phase can be directly precipitated from melt, as the growth rate is more than 22.35 mm/s. At the growth rate ranging from 1 to 5 m/s, the size of  phase doesn’t decrease due to the change of the solid transformation coefficient between  and  phases, which contributes to the peritectic transformation. With the increase of growth rate, the volume fraction of  phase firstly decreases and then increases. The primary dendritic arm spacing ( ) of Cu-70%Sn alloy and growth rate (V) have a relation of V0.325=199.5 m1.325s-0.325 as the growth rate is less than 50 m/s. While, at the growth rate from 50 to 500m/s, the value of V0.528 is equal to 676 m1.528s-0.528.

Surface alloying of Al ion implantation into Fe target with an ion energy of 120 keV has been investigated at the implantation temperatures of 250 and 500℃. The Al concentration--depth profiles and structure changes on the implanted Fe surface were determined by Rutherford backscattering spectroscopy (RBS) and X--ray diffraction (XRD), respectively. It is shown that at a dose of 1x1017ions cm-2, the Al ion implantation depths are 180 and 200 nm at the substrate temperatures of 250 and 500℃, respectively, while both the Al peak concentrations are 10% (atomic fraction). The intermetallic Al13Fe4 was formed at the temperatures of 250 and 500℃, the oxide AlFeO3 phase was also detected due to the contaminant oxygen. The model of effective heat formation was successfully adopted to interpret the intermetallics formation during Al ion implantation into Fe target at elevated temperature. The calculation results of concentration--depth profiles by using the mass transfer model are consistent with the experimental results.

The corrosion behaviours of the welded joints between steels Cr5Mo and A302 (Cr25Ni13) in the H2S containing solution (NACE TM--01--77 standard) were studied. In situ SEM observations revealed that compared with other zones the fusion boundary is the worst region for corrosion resistance due to the hydrogen induced disbonding, the corrosion resistance of the post--weld heat--treated joint is worse than that of the as--welded one and the fusion boundary with a broad scale has a stronger resistance for the hydrogen induced disbonding than the narrow one. These variations are related to the inhomogeneous microstructures, carbon diffusion, hydrogen--enrichment and stress concentration around the fusion boundary.

The structure, thermodynamic, hydrogen storage capacity, plateau pressure of LaNi5-xMx(M=Al, Mn) hydrides have been investigated. A relationship among x, the plateau pressure and the temperature is derived from the experimental data. The influences of the lattice parameter and cell volume, the stability of alloys on the hydrogen storage properties are discussed. As a result, LaNi5-xMnx alloys with larger cell volumes compared with LaNi5-xAlx alloys have lower plateau pressure. The anisotropic degree of the crystal volumes expansion in directions of the a and c axis and the change of stability of LaNi5-xMx alloys as a function of the Mn content are smaller than that as a function of the Al content. It is in agreement with the unconspicuous attenuation of hydrogen storage capacity in LaNi5-xMnx.

A chaotic local--region linear prediction model is constructed to predict the silicon content in hot metal of blast furnace (BF) No.1 at Laiwu Iron and Steel Group Co. and BF No.6 at Linfen Iron and Steel Group Co. As a result, more than 80.0% hit rate of prediction in the range of [Si]0.1% is attained with one--step prediction for both BF, and even 89.1% for sample (b) of BF No.1 at Laiwu Iron and Steel Group Co. The prediction precision is about 10-2. The result is helpful for industrial practice.

Two--dimension coupled model of the temperature filed, velocity field and density field was developed according to the geometry and technology parameters in hot filament chemical vapor deposition (HFCVD) diamond film. The spacial field during large area diamond film deposition was simulated using this model to study the influence of deposited parameters. The calculated results about the temperature and the mass flow density on the substrate are consistent with experimented ones. The inlet gas velocity obviously affects the uniformity of the mass flow density, and the other deposited parameters have little influence on the distributions of the temperature and mass flow density. The optimal hot filament geometry parameters to deposit high quality diamond films with an area of 100mmx100 mm are gained on the basis of the minimum temperature along hot filament array.

Scanning Auger microprobe (Auger) and X--ray photoelectron spectroscopy (XPS) have been used to investigate the fine structures of the Fe--Ni--C film covering as--grown diamond single crystal synthesized at high temperature and high pressure (HPHT). It is shown that the fine structures of iron and carbon atoms have greatly been transformed only in the inner part of the film adjacent to diamond; the binding energies in the valence bands of iron and nickel atoms on the film contacting diamond obviously increase compared to those in other regions of the film. Hereby, the inner part and diamond/film interface play an important role in the diamond growth under HPHT. It is suggested that the catalysis of iron and nickel to carbon should be finished on the interface or in the inner part of the film.