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Unusual relationship between extrusion temperature and tensile strength of extruded Mg–Al–Zn–Ca–Y–MM alloy
Journal of Alloys and Compounds ( IF 6.2 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.jallcom.2020.158051
Dong Hee Lee , Byoung Gi Moon , Young Min Kim , Sung Hyuk Park

Abstract This study investigates the effects of extrusion temperature on the microstructural characteristics and mechanical properties of an extruded Mg–9Al–0.8Zn–0.9Ca–0.6Y–0.5MM (AZXWMM91100) alloy and the resulting unusual relationship between the extrusion temperature and the tensile strength of the extruded material. All the extruded materials, i.e., alloy samples extruded at 325 °C, 350 °C, and 400 °C, have a fully recrystallized grain structure and contain abundant undissolved Al8Mn4Y, Al2Ca, and Al2Y particles. A small number of spherical nanosized Mg17Al12 precipitates are formed during extrusion, and their number density decreases with increasing extrusion temperature. The undissolved-particle bands, which are distributed parallel to the extrusion direction, act as obstacles to the growth of recrystallized grains during and after extrusion, which prevents excessive coarsening of grains at high extrusion temperatures. As a result, despite a large increase in the extrusion temperature from 325 °C to 400 °C, the average grain size of the extruded material increases only slightly, from 17.6 μm to 23.0 μm. Concurrently, the tensile strength of the extruded material increases from 183 MPa to 224 MPa; this directly proportional relationship between temperature and strength contrasts with the general inverse relationship between extrusion temperature and tensile strength. An increase in the extrusion temperature leads to an increase in the texture intensity of the extruded material; this increase is attributed to the following phenomena: (i) transition of the dominant dynamic recrystallization (DRX) mechanism from twinning-induced DRX and continuous DRX to discontinuous DRX, (ii) weakening of DRX through particle-stimulated nucleation, and (iii) promotion of the activation of prismatic slip. Therefore, the unusual extrusion temperature–tensile strength relationship for the AZXWMM91100 alloy is a combined result of the grain coarsening suppressed by the undissolved particles and strengthening of the texture hardening effect with the variation in the DRX behavior during extrusion.

中文翻译:

挤压镁-铝-锌-钙-Y-MM合金的挤压温度与拉伸强度之间的异常关系

摘要 本研究研究了挤压温度对挤压 Mg-9Al-0.8Zn-0.9Ca-0.6Y-0.5MM (AZXWMM91100) 合金的显微组织特征和机械性能的影响以及由此产生的挤压温度与拉伸强度之间的异常关系。挤压材料的强度。所有挤压材料,即在 325 °C、350 °C 和 400 °C 下挤压的合金样品,都具有完全再结晶的晶粒结构,并含有大量未溶解的 Al8Mn4Y、Al2Ca 和 Al2Y 颗粒。挤压过程中形成少量球形纳米Mg17Al12沉淀物,其数量密度随挤压温度升高而降低。平行于挤出方向分布的未溶解颗粒带,在挤压过程中和挤压后充当再结晶晶粒生长的障碍,从而防止在高挤压温度下晶粒过度粗化。结果,尽管挤出温度从 325 °C 大幅增加到 400 °C,但挤出材料的平均晶粒尺寸仅略微增加,从 17.6 μm 增加到 23.0 μm。同时,挤出材料的拉伸强度从183 MPa增加到224 MPa;温度和强度之间的这种正比关系与挤出温度和拉伸强度之间的一般反比关系形成鲜明对比。挤压温度的升高导致挤压材料的织构强度增加;这种增加归因于以下现象:(i) 主要动态再结晶 (DRX) 机制从孪生诱导的 DRX 和连续 DRX 转变为不连续 DRX,(ii) 通过粒子刺激成核减弱 DRX,以及 (iii) 促进棱柱滑移的激活。因此,AZXWMM91100 合金不寻常的挤压温度-拉伸强度关系是未溶解颗粒抑制晶粒粗化和织构硬化效应增强以及挤压过程中 DRX 行为变化的综合结果。
更新日期:2020-11-01
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