Molecular dynamics/statics study of the atom process and relevant energy for formation of the twins in <111> grown copper films have been carried out. An embedded atom method (EAM) potential of Finnis-Sinclair type was employed. The results show that the deposited atoms on <111> grown copper films can form fcc domains or hcp domains in different localities. When atoms deposited at hcp positions, the energy of the system is higher than that at fcc positions. The increment decides the probability of twin formation. It is further indicated that the mismatch energy of the deposited atom is greatly affected by previously formed \{111\} twin plane. When the distance between surface and the twin plane underneath is smaller than three atomic layers, the mismatch energy is as high as that for perfect crystal of aluminum which does not form twins in <111> growth, and hence the probability for formation of twin is very low. As the distance increases, the mismatch energy rapidly decreases, and even becomes slightly lower than that on {111} plane of perfect copper crystal after the distance reaches twelve atomic layers, implying that the probability for formation of twin plane is higher than that on {111} surface of perfect crystal.

The γ/γ lamellar interfaces play a critical role in the mechanical properties of γ+α2 two-phase TiAl-based alloys. The transformation matrices necessary for indexing the crystallographical orientations of γ lamella are systematically calculated. Based on these calculated matrices, the interface types between neighboring γ laths could be determined unambiguously. The frequency of different interface types in a Ti-47Al-2Mn-2Nb (atomic fraction, %)+0.8TiB2(volume fraction, %) alloy was measured by means of convergent-beam electron diffraction and compared with the frequency distribution in binary TiAl alloys.

Based on the finite element analysis of wheel/rail friction and experimental data of the phase transformation in wheel steel, the mechanism of wheel thermal fatigue under high speed and heavy load conditions was simulated. The changes of temperature field under several operating conditions (loading, braking time, running speed) have been calculated, and its affection on phase transformation zone in wheel tread has been discussed. The peak temperature of contact zone may reach over austenitizing temperature under heavy load sliding. The depth of austenized zone may reach at 1mm under the wheel tread. The increase of sliding speed does not affect the depth of phase transformation zone, but increase the probability of phase transformation. Both the peak temperature and the size of phase transformation zone increased with increased loading.

Temperature memory effect of a prestrained TiNi alloy under constraint condition was studied by differential scanning calorimetry (DSC). Results showed that the transformation temperature range of the TiNi alloy can be significantly enlarged upon prestraining and constrained heating, which makes the temperature memory effect operational also in an enlarged temperature window. Furthermore, the temperature memory effect of the prestrained and constrained TiNi alloy is more accurate than that of a TiNi alloy in free conditions. The dislocations at the interface between the parent phase and the remaining martensite, and the self--accommodating process near the interface are thought to be the mechanism for the temperature memory effect.

Elastic-plastic large deformation finite element (FE) analysis was conducted on the crack-tip stress field of pure Al sheet in LY12/Al/LY12 sandwich specimen with a strength mismatch and fatigue pre-crack under plane strain condition. The results show that, in the condition of small scale yielding (SSY), the peak value of loadings linearly increases with decreasing pure Al sheet thickness. Plastic deformation zone in Al sheet constrained by interfaces will spread along the crack-tip ligament parallel to the two interfaces instead of a spindle-like in a constraint-free metal, and this tendency becomes more remarkable with decreasing pure Al thickness. The maximum triaxial constraint and the tensile stress continue to rise with either increasing load or decreasing pure Al thickness. The high triaxial constraint in the Al sheet results in cavitations and micro-cracks as well as brittleness even local cleavage of pure Al sheet.

The local stress field of actual particles in magnesium matrix composites reinforced with SiC particles (SiCp) was simulated using the finite element method. The result suggests that the local stress fields of particles with different shapes have great difference and some particles may fail under a lower stress. If the volume fraction of particles is less, other particles have little influence on the local stress field of a certain particle. Therefore, the local stress field of a particle with a given shape can be simulated. Magnesium matrix composites reinforced with SiCp were prepared by powder metallurgy. Fracture analysis was performed and was compared with the particle failure analysis carried out by finite element method.

In order to investigate the carbon diffusion during the deformation induced ferrite transformation, the electron probe microanalysis technique was used to measure the carbon concentration distribution in the microstructure of the specimen which experienced a hot compression process on the thermomechanical simulator (Gleeble 1500). The measurement results indicated that the carbon concentration was significantly supersaturated in the deformation induced ferrite grains, which means that there was no carbon atoms diffusion from the ferrite to the austenite during the deformation induced ferrite transformation. According to the thermodynamics analysis, there is no need for the carbon atoms to diffuse from the ferrite to the austenite during the transformation, because the accumulated stored energy has become the unique driving force when the deformation temperature is higher than the austenite-ferrite equilibrium transformation temperature Ae3. diffusion, electron probe microanalysis

Under several nonproportional cyclic elliptic and rhombic paths with different ratios between the lengths of long axes and the short axes, the effects of the path shapes of the cyclic strain and cyclic stress, the equivalent stress and strain amplitudes for the paths, the mean strain and their loading history on the nonproportional cyclic deformation behavior were experimentally investigated for SS304 stainless steel at room temperature. The experimental study shows that the cyclic plastic behavior of SS304 stainless steel depends strongly on the path shapes of the cyclic strain and cyclic stress, the equivalent stress and strain amplitudes for the paths and their loading history.

Nanostructured surface layer was synthesized on 316L stainless steel by means of the surface mechanical attrition treatment (SMAT), the microstructural evolution was examined by using XRD and TEM. A grain refinement mechanism was proposed as follows: the dislocations in the austenite grains annihilate and recombine to form dislocation cells; the increment of strain and strain rate induces mechanical twinning, and lamellar microstructures form; the microstructures translate gradually from lamellar to equiaxed by means of the development of the dislocations in the twins, accompanying by the reduction of grain size and the increment of misorientations; finally, nano--scale grains with equiaxed shape and random crystallographic orientations form. Besides, the effects of staking fault energy on the deformation and grain refinement behaviors were discussed.

Hot-rolled acicular ferrite pipeline steel plate can be further strengthened by aging treatment. After an aging treatment at 600 ℃ for 10 h, the acicular ferrite pipeline steel plate is strengthened to the level of X 100 while its impact toughness does not obviously decrease. At the same time, its H2S cracking resistant ability is also improved obviously. All these can be attributed to the additional precipitation of micro-alloyed carbonitrides, the transformation of martensite/austenite (M/A) islands to tempering martensite and the improvement of the uniformity in acicular ferrite microstructure during aging treatment.

In order to investigate the effects of helium on the excess point defects and secondary defects processes in low activation Fe-Cr-Mn(W,V) alloys during electron beam and electron-He+ ion dual beam irradiation, the in situ observation was carried out using a high voltage electron microscope connected with an ion accelerator. The experiment result indicates that the interaction between helium and point defect clusters formed in the early stage of irradiation affected the secondary defects (dislocation, dislocation loop and void) formation. The helium enhances the increase in dislocation density and void nucleation site obviously. As a result, the void swelling in Fe-Cr-Mn(W,V) alloy was enhanced. The mechanism of interaction between helium and point defects produced by irradiation was also discussed.

The propagation processes of indentation cracks in air and water under a sustained load for a PZT-5 ferroelectric ceramics have been investigated. The results show that the indentation cracks could propagate in air and water and arrest after about 120 h. As a result, the crack propagation rates and threshold stress intensity factors for crack arrest in air and water were obtained, and revealed anisotropy. The anisotropy of susceptibility to stress corrosion cracking is relative to the anisotropy of the fracture toughness. The fracture toughness of the crack perpendicular to the poling direction is smaller than that parallel to the poling direction, i.e., KcICda/dt. Stress corrosion cracking in water is more susceptible, i.e., da/dt is larger and KISCC is smaller, than that in air.

The stress corrosion cracking (SCC) behaviors of X70 pipeline steel in near-neutral pH solutions at different temperatures and applied potentials are studied with slow strain rate testing (SSRT). The results show that the cracking mode of X70 pipeline steel in near-neutral pH solutions is transgranular at different temperatures with the feature of quasi-cleavage. The susceptibility to SCC increases as the applied potential moved towards the cathodic direction. Hydrogen induced cracking (HIC) dominates the process. The value of pH decreases slightly with decreasing temperature of the solution, and the susceptibility to SCC increases.

The martensitic and magnetic phase transformations in polycrystalline non-stoichiometric Ni52Mn21+xGa27-x(x=0-5) alloys were investigated. The experimental results show that the alloys exhibit ferromagnetic and thermo-elastic martensitic transformations. The martensitic transformation temperatures (Ms) increase with increasing Mn content and reach above room temperature when x>4. The martensitic transformation hysteresis (δT) decrease with increasing x. The magnetic phase transformation temperatures (Curie temperature TC increase with an increase of x within a small range and keep around 348 K when x>2. In addition, an alloy composition of Ni52Mn25Ga23 with potential practicality was obtained, which has a higher martensitic transformation temperature than room temperature and a transformation hysteresis of only 5 K.

The crystals of Ni2MnGa were prepared by high temperature gradient zone-melting unidirectional solidification. Through altering the growth velocity, the temperature gradient and the zone-melting length, a flat solid-liquid interface can be obtained, and a single crystal was successfully prepared. The crystal growth competition was observed in Ni50Mn29Ga21 alloy. No obvious composition macro-segregation was detected. In X-ray diffraction pattern only 400 and 004 peaks of the tetragonal martensitic structure appear, showing the preferred orientation along <100> of the high-temperature cubic austenite Ni2MnGa. DSC and TG methods were applied to describe the distributions of the martensitic transition temperature and Curie temperature along the solidified axis of the Ni50Mn29Ga21, no obvious change for Curie temperature and about 10℃ increase for the martensitic transition temperature were observed, further indicating the homogeneity of the composition along the growth axis.

Elements Si and B in the Ti50Ni22Cu18Al4Si4B2 alloy are substituted with Sn to form the Ti50Ni22Cu18Al4Snx(Si0.67B0.33)6-x (x=0,3,6) series alloys. In all cases, mechanical milling of the prealloyed fragments results in the amorphization of the alloys. With increasing the Sn content in the alloys, the fraction of residual α-Ti crystallites in the final milled product was reduced. For the Ti50Ni22Cu18Al4Sn6 alloy, in which the Si and B are completely replaced with Sn, the nearly complete amorphization is achievable. A single amorphous phase, similar to the melt-quenched glass, formed in the milled alloy. Such a ball-milled glassy alloy exhibits a large supercooled liquid region about 66 K.

A numerical simulation was carried out for Cd0.96Zn0.04Te crystal growth using vertical Bridgman method (VBM). Effects wave parameters of the accelerated crucible rotation technique (ACRT) on the solid-liquid interface concavity and the solute segregation were investigated. The results show that for the four kinds of wave parameters, the ACRT results in an uniform solute concentration field in the melt in the front of the solid-liquid interface. However, ACRT wave parameter has crucial effects on both the solid-liquid interface shape and the solute segregation in the crystal. With a suitable wave parameter, the ACRT can make the solid-liquid interface concavity increase a little, or even not increase, and decrease the radial solute segregation in the single crystal extraordinarily, even to be equal to zero. On the contrary, with an unsuitable wave parameter the ACRT can make the solid-liquid interface concavity increase in a great deal, even up to six times, and increase the radial solute segregation significantly. Moreover, the ACRT increases the axial solute segregation apparently with all the four kinds of wave parameters mentioned in this paper.

A high frequency amplitude-modulated magnetic field (AMMF) generator that can produce rectangle, triangle and sine waves has been invented, and the magnetic field inducted in the mold by the generator was measured. The amplitude-modulated magnetic field has been applied in mold oscillation-less electromagnetic continuous casting (MOLECC) process, the experiment results show that under rectangle, triangle and sine wave AMMF, when the modulated wave frequency is a little less then the intrinsic frequency of the experimental system the intermittent contacting distance is the greatest, the mold flux lubricating is the best, the continuous casting withdraw resistance is the least and the surface quality of billets is better relatively. Among the three wave types, the sine wave is better than the rectangle and triangle waves for deducing the withdraw resistance and improving the billets surface quality.

WC-10%Co (mass fraction) cemented carbide with an average grain size of 120 nm are fabricated by means of electric-discharge compacting (EDC) the nano-crystalline WC-10%Co powders which were synthesized by spray conversion process (SCP). Microstructure and mechanical properties of the cemented carbide are investigated. Because of short holding time during EDC, the grain growth is retarded. It is found that the dispersed micro-size pores are contributed to the high fracture toughness of the samples besides the bridging ligament mechanism.

The problems related to the product strength and fine particle content are the main tasks to be solved in sandy alumina production. Carbonization product, Al(OH)3, was investigated through the application of additives to sodium aluminate liquors. A systematic study was made of the effects and mechanism of surfactants on product median diameter and attrition index quantitatively. It has been determined that some appropriate additive at certain concentration can significantly decrease the fine particle content, enhance the agglomeration process, and improve the product strength. For instance, additive CF2 at 200 mL/L increases the mean particle size by about 12 μm, decreases the content of particles with less 45 μm by 17% and the attrition index by 10% respectively. The crystal morphology indicates that the additives can accelerate the aggregation and inter-growth of crystal units, as a result, the product Al(OH)3 presents a mosaic crystal structure close to global shape.