On the assumption that plastically deformed grains multiply irreversibly during tensile deformation, a yield model of polycrystalline metal and explicit relationships between stress σ and deformation time t were proposed. When t is small enough, the yield stresses can be formulated approximately. According to the different values of the ratio of initially deformed grains, tension rate, grain diameter and other parameters. several typical yield modes can be described. some phenomena can be explained quantitatively, which are in better agreement with Hall-Petch formula and the experiments.

It was observed first in this test that the stabilized dislocation cell and wall structures had been formed on near fatigue threshold of physcial short crack in dual-phase steels. There was a probability of forming dislocation cell on ferrite-martensite interfaces in long crack growth threshold. where the dislocation lines were more dense, there were the dislocation lines of single(R = 0,-1) and cross slip(R=-1) in the second stage of long crack growth ;there were obviously rare and lengthened dislocation lines of single and cross slip in the third stage of long crack growth. It is indicated that the dislocation morphologies of fatigue crack tip were the products of strain history. The dislocation cell and wall structures were substable on near physical short crack threshold. it was constituted into dynamic balance with cyclic stress-strain on threshold, and also was one of microstructural parameters.

Thermodynamic analysis for shear formation of bainitic ferrite in carbon-depleted regions of austenite is conducted. The driving force of bainitic formation in carbon-depleted region increases with the reduction of carbon concentration in this region and can overcome the energy resistance. The critical driving force (absolute value) at Bs temperature is 470─1200 J/mol. The freshly-formed bainitic ferrite is with partial supersaturation of carbon, which increases with decreasing the reaction temperature. Finally,it is concluded that the shear mechanism of bainitic formation in carbon-depleted region is thermodynamically feasible within the whole temperature range of bainitic reaction.

The yield and ultimate strengths increase with the amount of Zr increasing. If an additive of Zr less than 0.7 at.-％. the elongation of the alloy increases with Zr content growing. If Zr added up to 1.2 at-％. the effect of Zr improving ductility of the alloy is fall off. Auger study indicated that the amount of Zr segregated to the GB is about 3 times greater than that in the bulk. SEM investigation showed that the fracture mode changes from intergranular in Ni-24.0 Al and Ni-24.0 Al-1.2Zr (in at.-％) alloys to the mixed of interand trans-granular in Ni-24.0 Al-0.3 Zr and Ni-24.0 Al-0.7 Zr (in at.-％) alloys. These results manifested that the effect of Zr improving the ductility in Ni3Al has strong relationship with the segregation of Zr at GB.

Effect of 3％ pre-straining of austenite on the improvement of SME in Fe-29.9％ Mn-6.0％Si has been studied over the temperature range of 573-1073 K. Results show that recovery strain (εtr). shape recovery ratio (η) and strain corresponding to the saturation εtr for the solution treated samples deformed at room temperature have been improved significantly by pre-straining of austenite. The ηfor the samples with ～2.5％ deformatin at room temperature increases with pre-straining temperature and the maximum ηcan be reached by pre-straining at 973 K when dynamic recrystallization has just occurred. After pre-straing at 973 K, the maximum εtr has been increased from 1.7％ for solution treated sample to 3.8％ and the complete recovery strain can reach 2.2％. It is believed that the pre-straining of austenite is to decrease the critical stress for the formation of ε martensite.

The effect of Bi segregation at grain boundary on the fracture behaviour and grain boundary embrittlement was studied by using orientationcontrolled Cu bicrystals with [001] symmetrical tilt boundary.The results indicate that the fracture behaviour and fracture stress of Cu-Bi bicrystals depend strongly on the misorientation, and the grain boundary embrittlement is not related to the density of coincidence site lattice of the grain boundary but to the unsegregated grain boundary energy. the higher the grain boundary energy- the stronger the grain boundary embrittlement. The dependence could be explained by considering the boundary-dependent segregation of Bi atoms.

The compressive superplastic tests at constant temperature were carried out on flame sprayed FeNiBSi alloy coating on GCrls steel. The relationship of superplastic deformation between the coating and the substrate was investigated. After deformed superplastically, the internal cavities in the FeNiBSi alloy coating may be disappeared. and the bonding interface between the coating and the substrate may be metallurgically welded.

The hydrogen charging curves and releasing curves have been measured by ERD and PAS. The hydrogen charging rate for the bearing B steel is 4 times faster than that for the unbearing B steel. Hydrogen atoms in bearing B steel are mostly trapped by defects (grain boundary. interface of boride, etc.). but in unbearing B steel are mostly dissolved atoms. However, hydrogen releasing rate when annealing at 220℃for unbearing B steel is about 3 times faster than bearing B steel. After annealing at 220℃.the peak of hydrogen in bearing B steel has been moved towards the surface by 25 nm. but in unbearing B steel the movement of the peak is about 50-90 nm. These results indicate that trace B in the steel can retard hydrogen atoms from diffusing towards interface of the emalled coating and the steel.So that trace B can get rid of the busting of the coating during or after the baking process.