Effect of age hardening on the deformation behavior of an Mg-Y-Nd alloy: In-situ X-ray diffraction and crystal plasticity modeling
Effect of age hardening on the deformation behavior of an Mg-Y-Nd alloy: In-situ X-ray diffraction and crystal plasticity modeling
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DOI：
10.1016/j.msea.2015.01.069
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发表时间：
2015-03-25
期刊：
影响因子：
6.4
通讯作者：
Knezevic, Marko
中科院分区：
文献类型：
--
作者：
Lentz, Martin;Klaus, Manuela;Knezevic, Marko
本文研究了挤压Mg-Y-Nd （WE54）合金在挤压态和时效条件下的变形行为。通过250℃时效硬化16和500 h或400℃退火24 h，晶粒内或晶界处形成析出相。为了表征时效硬化条件下的微观组织变化，我们采用了电子背散射衍射、透射电子显微镜和光学显微镜。在挤压态材料中，与其他镁合金相比，我们观察到{10 (1)/ bar2}< 10 (11) / bar>的张力孪晶活性非常低。析出硬化后拉伸孪晶活性显著提高，同时降低了固溶体中合金元素浓度。与微观结构观察相一致，孪晶活度的增加在压缩流动曲线中明显表现出来。挤压态和16 h/250℃退火样品在拉伸过程中表现出典型的与晶体滑移相关的硬化速率降低，而500 h/250℃和400℃退火样品则表现出与孪晶相关的硬化速率增加的特征。为了确定不同热处理对单个滑移和孪生模式的影响，在加载和弹塑性自一致建模过程中进行了原位能量色散x射线同步加速器衍射实验。我们发现，在{10 (1)/ bar0}（α）上的板状析出物比其他滑移体系更坚硬，而在500 h 250℃和24 h 400℃样品中溶质浓度的降低导致{10 (1)/ bar2}< 10 (11) / bar >张力孪晶的临界分解剪应力显著降低。(C) 2015 Elsevier B.V.版权所有
The present study investigates the deformation behavior of an extruded Mg-Y-Nd (WE54) alloy in as-extruded and aged conditions. Via age-hardening at 250 degrees C for 16 and 500 h or annealing treatments at 400 degrees C for 24 h, precipitates are formed within the grains or at the grain boundaries. To characterize microstructural changes with the age-hardening conditions, we employ electron-backscattered diffraction, transmission electron microscopy, and optical microscopy. In the as-extruded material, we observed an uncommonly low activity of {10 (1) over bar2}< 10 (11) over bar > tension twinning in comparison with other Mg alloys. The tension twinning activity substantially increased after precipitation hardening and the accompanying reduction of alloying element concentration in solid solution. Consistent with the microstructural observations, the increase in twin activity clearly manifests in the compression flow curves. While the as-extruded and 16 h/250 degrees C samples exhibited a classical decreasing hardening rate throughout straining associated with crystallographic slip, the 500 h/250 degrees C and the 400 degrees C annealed sample featured a characteristic increase in the hardening rate associated with twinning. In order to determine the impact of the different heat treatments on the individual slip and twinning modes, in-situ energy-dispersive X-ray synchrotron diffraction experiments during loading and elasto-plastic self-consistent modeling were conducted. We find that plate-shape precipitates on the {10 (1) over bar0}(alpha), planes harden < a > basal slip more than the other slip systems, while the reduced solute concentration in the 500 h 250 degrees C and 24 h 400 degrees C samples results in a significant decrease in the critical resolved shear stress for {10 (1) over bar2}< 10 (11) over bar > tension twinning. (C) 2015 Elsevier B.V. All rights reserved.