Effect of electroplastic treatment on microstructure and texture changes of a cold rolling AZ31 strip
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1170-R05-15
Effect of electroplastic treatment on microstructure and texture changes of a cold rolling AZ31 strip Lei Guan and Guoyi Tang Advanced Materials Institute, Graduate School at Shenzhen, Tsinghua University, Shenzhen, 518055, People’s Republic of China;
ABSTRACT The effect of the electropulsing on recrystallized microstructure and on texture evolution of a cold rolling (CR) AZ31 strip was studied with the help of light microscopy and X-ray diffraction technique. It was exciting that the completed recrystallization state of sample subjected to the electropulsing treatment (EPT) could be obtained rapidly in ~7s with the basal texture weakened. The favoring mechanism of static recrystallization (SRX) of MPT could be attributed to the coupled action of the thermal and athermal effects, thereinto, the latter one activated dislocation climb effectively. INTRODUCTION As a light-weight structural metal with high specific strengths, magnesium alloy becomes the most attractive material in applications of transportations and mobile electronics for reducing weight. However, Mg alloys exhibit limited ductility at room temperature because of presence of limited slip systems. Grain refinement is a promising technique for improving the strength and ductility of wrought magnesium products due to the strong influence that grain size has on the mechanical properties. Proper rolling combined with suitable annealing treatment can produce fine-grained microstructure. However, the conventional heat treatment in a furnace requests a long-time heating ranging from 200 to 400 , which often results in not only grain coursing but also the higher inconceivable cost and low efficient of output. There is a pressing need to seek a new method of heat treatment for as-rolled wrought magnesium alloy strip. In order to improving microstructure and properties of materials, electropulsing treatment (EPT) has been applied for many years. EPT was used during annealing of cold-worked copper to obtain fine recrystallized grains and to retard the formation of annealing twins [1-5]. In the case of EPT, the recrystallization mechanism could be attributed to the coupled action of thermal and athermal effects [6]. While there is considerable research work [4-7] on grain refining of materials employing EPT, few studies have focused on the texture evolution of magnesium alloys during EPT. In this work the effect of electropulsing treatment on texture development of AZ31 strip is reported.
EXPERIMENT A commercial AZ31 (Mg-3 wt pct Al-1 wt pct Zn) alloy was selected to conduct the experiments. The as-received AZ31 strip with width of 2.96 mm and thickness of 1.5 mm was obtained by process sequence of extrusion of bar. After annealed at 573K for 1hour, the extruded strip was then cold-rolled (C.R.) in single pass to 1.35, 1.17 and 1.03 mm thick corresponding to 10%, 22% and 31% reduction for EPT with various parameters of electropulsing (see Table I). Cold rolling of 31% thickness reduction per pass was operated without any side-crack. The schematic vie
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