B.L. Wu

The Influence of Texture and GBCD on Stress Corrosion and Intergranular Corrosion in 2024 Aluminum Alloy

The recrystallization texture, grain boundary character distribution (GBCD) and their influence on the stress corrosion cracking and intergranular corrosion of 2024 aluminum alloy were investigated. Results showed that the texture of Specimen A1 is characterized by the retained coldrolling texture; while Specimen A3 has strong recrystallized cube texture and high frequencies of CSL grain boundaries (especially S7), which shows high stress corrosion and intergranular corrosion resistance.

Excellent cold rollability in a single pass of an Mg-4Er (wt.%) alloy

Abstract Sheets of Mg-4Er (wt.%) alloy were prepared by multi-pass hot rolling and subsequent annealing. The annealed sheets could be cold-rolled to a high reduction of 95% (corresponding to a rolling strain of 3) by one-pass rolling at room temperature. The evolution of the deformed microstructure of Mg-4Er alloy was investigated during the cold-rolling process. The results suggest that multiple dislocation slips are the predominant deformation mode responsible for the remarkable rolling plastic strain. Meanwhile, the multiple dislocation slips are favorable to a continuous restoration process, which can accommodate the rolling strain by absorbing the deformation energy.

Nanocrystallization and Texture Transformation in the Surface Layer of Copper Induced by Surface Mechanical Attrition

A nanostructured surface layer was synthesized in a pure copper plate by means of surface mechanical attrition (SMA). The evolutions of microstructure and orientation were examined by using XRD, TEM and ODF. The microstructural evolution with the treatment time can be divided into two stages: the first is characterized by a formation of nc grains with small to medium misorientations in the surface layer and a texture transformation from rolling type to shear one in the near-surface layer, and the second by a significant increment of misorientations between the nc grains and a texture transformation from shear type back to rolling one. It might be reasonably deduced that shear stress can effectively induce grain refinement, and the combination of shear and compress stresses might be helpful for the increment of grain boundary misorientations.

Stress-Induced Lattice Transit Behavior in a Cold-Rolled Cu-Al-Mn Two-Way Shape Memory Alloy

The effect of cold rolling on two-way shape memory was investigated by x-ray diffraction technique and TEM in a Cu-18Al-10.5Mn (at.%) alloy. Cold rolling leads to a preferred orientation distribution on the stress-induced martensite with 6M-structure, which leads to the dependence of two-way shape memory on the specimen directions. The relationship of stress state and anisotropy of 6M-structured martensite lattice inside cold rolling deforming region is elucidated through analyzing the deformation process-related variant selection according to original grain orientation.

Grain Refinement of an Al-Cu-Mg Alloy by Microalloying and Common Thermo-Mechanical Treatment

Heavy deformation plus micro alloying could be an effective way to obtain ultrafine grain structure of metals. In the present work, an Al-Cu-Mg alloy was microalloyed with Zr to obtain homogeneous precipitates and then heavily deformed by conventional forging at high temperature. The possible refining processing routes were studied and the superplasticity behaviors of the alloy was investigated. Results show that the micro alloyed alloy can be stably refined to 3-5μm under conventional processing routes. The Al-3Zr precipitates act both as additional sites to enhance recrystallization nucleation rate and pins to impede grain growth to increase the thermal stability of the fine grain structure. However, as the Al3Zr precipitates remains along grain boundaries, the superplastic capability of the material is not high. At 430°C with 1×10-4S-1 strain rate, the elongation obtained was 260%.