Microstructural Analysis and Texture Evolution of the CVCEDed AZ31 Magnesium Alloy by Hot Rolling
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JMEPEG https://doi.org/10.1007/s11665-018-3560-y
Microstructural Analysis and Texture Evolution of the CVCEDed AZ31 Magnesium Alloy by Hot Rolling Xu Bo Li, Feng Li, and Xue Wen Li (Submitted March 7, 2018; in revised form June 10, 2018) Grain refinement is one of the important methods to improve the performance of magnesium alloy sheets. This paper attempts to prepare the billets of AZ31 magnesium alloy sheets by continuous variable crosssection direct extrusion (CVCDE) and then prepare sheets by rolling. The results show that the average grain size of the sheets rolled from extruded products by CVCDE with 2 interim dies reduced by 30% and the tensile strength increased by 12.6% compared with the sheets rolled from extruded products by traditional extrusion (CE), which is related to the dislocation multiplication in the corresponding conditions. The high dislocation density hinders the plastic deformation of the material, which is one of the internal factors that cause the increase in the strength of the material and the decrease in the plasticity. In addition, the basal surface of a lot of grains of the sheets rolled from extruded products by CVCDE with 2 interim dies is parallel to the RD-TD plane and the strength of texture is high. Meanwhile, the value of average Schmid factor of the sheets rolled from extruded products by CVCDE with 2 interim dies along the rolling direction is lowest, which result in lower plasticity. The above research provides a new idea for the development of high-performance magnesium alloy sheets. Keywords
continuous variable cross-section direct extrusion (CVCDE), magnesium alloy, microstructure, rolling, texture
1. Introduction Magnesium alloy is one of the potential lightweight materials which can replace steel and aluminum alloy components because of its excellent comprehensive properties, so it has been widely used in recent years (Ref 1-3). It is well known that sheet and strip account for more than 70% of nonferrous metal products. In addition, compared with the cast magnesium alloy, the wrought magnesium alloy has more finer and uniform microstructure and good mechanical properties (Ref 4-6). So rolling has attracted much attention in recent years as an ideal process for manufacturing magnesium alloy sheet products (Ref 7-9). Pan et al. (Ref 10) reduced the AZ31B magnesium alloy plate thickness from 4 to 0.8 mm in 7 passes by online heating rolling at temperatures ranging from 443 to 623 K with intervals of 60 K. The experimental results suggest that the fracture elongation value increases rapidly at temperatures below 563 K and then tends to be stable between 563 and 623 K. However, the tendency of yield strength and ultimate tensile strength is just an opposite one. Wang et al. (Ref 11) investigated the effect of rolling process conditions on the microstructure of LA51 and LA51-0.5Y. The results show that the addition of 0.5%Y could improve the deformation resistance of the LA51 alloy. By comparison, the effect of Y on ultimate tensile strength of as-rolled alloys is more obvi
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