The formation,development and microstructure of shear localization formed during dynamic high speed tornsional testing by split Hopkinson bar with a average strain rate range of 600,650 and 1500 s-1 have been investigated in low-carbon steels.The results showed that the shear localization is sensitive to the strength of the steel.The higher the strength of the steel,the earlier the shear localization occurs.The observations by TEM indicated that the formation and development of the shear localization involved a series of the crystallographic and non-crystallographic events including the dislocation emission from the interfaces between the precipitate and matrix,forming network,cell and tangled structures of the dislocations;the misorientation formation arising from the large accumulated plastic strain in a local area in the band and the growth and coalescence of the microcracks in the band leading to a sharp drop in the load-carrying capacity of the deformed material.

The structure variety of directionally solidified eutectic Pb-Sn alloy under step and linear change of specimen displacement velocity was experimentally observed.The experiments were conducted on a directional solidification apparatus with an electronic varying velocity programmer for specimen displacement,which was designed and constructed by the authors.The experimental results show that,when the eutectic specimen moves with a slow and linear increase or decrease in velocity,the average laminar spacing of the directionally grown eutectic changes through progressive branching or merging of the eutectic laminae of both the two phases.The variation curves of the eutectic growth rates are approximately symmetric for the increase and decrease in the displacement velocity at the same acceleration.

Dendrite evolution from cellular structures of directionally solidified Al-2wt-% Cu and Al-4 wt-% Cu specimens under step and linear change of displacement velocity was studied with an improved experiment apparatus of directional solidification.The experimental results show that, although the dynamic process of cellular to dendritic transition becomes slow with decrease in the velocity change of specimen displacement,the instability and branching of the cellular structure will rapidly develop a dendritic strucutre after a certain disturbance of the cellular morphology.These dendrites could have various morphologies which are related to the acceleration.

Microstructure,morphology and composition of the phases in 2 kW laser remelted Al_2O_3-13wt-%TiO_2 ceramic coatings on ICr18Ni9Ti substrate were examined by using electron diffraction, diffraction contrast image and EDAX. Results showed that TiO_2 and a part of Al_2O_3 formed Al_2TiO_5 and a superlattice phase appeared in the ceramic layer;a little alloy element of substrate permeated into α-Al_2O_3 and replaced only a part of Ti in Al_2TiO_5.The distribution and morphology of α-Al_2O_3 and Al_2TiO_5 were related with the distance from surface.The shape of Al_2TiO_5 was strip near surface and block near substrate,and the farther from surface,and the more Al_2TiO_5 in the coatings.

Fully reversed strain-controlled tension-compression tests were performed at room temperature to study cyclic-deformation properties of Ni_3(Al,Zr) single crystal.Both cyclic strain hardening and a tension-compression flow stress asymmetry were recorded,the stress asymmetry becomes more prominent as the strain amplitude becomes larger;the cyclic hardening can divide into initiation and saturation stages.TEM observation showed that there are a profusion superlattic intrinsic stacking faults(SISFs) in fatigued Ni_3(Al,Zr) single crystal samples.The cyclic strain hardening is explained by the dislocation structure.

The five dispersed intermetallic phases in as-extruded rapidly solidified (RS)Al-8-32Fe-3.4Ce alloy during the heat-exposure produre have been characterized by conventional TEM and X-ray energy dispersive spertrum analysis.A new phase which belongs to a rhombohedral structure with parameters of a=1.4 nm and c=0.7 nm,and with a chemical composition of Al_8Ce was observed.

A kind of oxide dispersion strengthened(ODS) ferritic steel Fe-Cr-W-Ti-Y_2O_3 with low swelling and high strength properties has been developed and its behaviour and characteristic of the irradiation damage have been systematically studied.Results of electron irradiation indicate that Y_2O_3 dispersed oxide particles were stable under these irradiation conditions.During irradiation,two kinds of dislocation loops with b=a〈100〉-type and b=a/2〈111〉-type formed.At 673 K as the dose increasing from 5 to 17.5dpa,the void swelling increased from 0.1% to 0.35%.In the irradiated region there were not significant concentration changes of the solute atoms such as Cr,W and Ti near grain boundacy.