The role of atomic scale segregation in designing highly ductile magnesium alloys
The role of atomic scale segregation in designing highly ductile magnesium alloys
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DOI：
10.1016/j.actamat.2016.06.024
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发表时间：
2016-09-01
期刊：
影响因子：
9.4
通讯作者：
Al-Samman, T.
中科院分区：
文献类型：
--
作者：
Basu, I.;Pradeep, K. G.;Al-Samman, T.
两种固溶体二元镁稀土合金，Mg-1wt。% Gd和Mg-1wt。对% Dy进行大应变热轧，然后在不同温度下再结晶退火60 min。Mg-1Gd中的再结晶和晶粒长大导致变形织构的逐步变化，突出表现为轧制过程中形成的基本织构成分完全消失。Mg-1Dy退火后织构变化不明显，随着退火温度的升高，变形基织构逐渐软化。在退火过程中有利的re织构的发展被认为是溶质偏析到平面缺陷（如晶界）的结果。原子探针层析观察到Gd原子比Dy原子表现出更高的晶界偏析倾向。在退火过程中，Gd的偏析行为增强，表现为离基底取向的再结晶比变形组织产生的基底取向的生长优势更强，在更高的退火温度和更长的退火时间下，晶粒继续以不连续的方式生长。Mg-1Dy在再结晶和晶粒长大过程中没有明显的生长优势。两种稀土元素之间的偏析作用和由此产生的退火织构演变强烈影响了两种合金的室温拉伸塑性。Mg-1Gd似乎表现出伴随的沉淀硬化效应，从而表现出更高的抗拉强度和增强的塑性。这项工作表明，利用稀土元素作为一种有效的机制，有选择地利用晶界特征来定制热机械加工过程中的微观结构，从而提高镁合金的力学性能，这是令人兴奋的可能性。(C) 2016材料学报Elsevier Ltd.出版。版权所有。
Two solid solution binary magnesium-rare earth (RE) alloys, Mg-1wt.% Gd and Mg-1wt.% Dy were subjected to large strain hot rolling followed by recrystallization annealing at different temperatures for 60 min. Recrystallization and grain growth in Mg-1Gd led to stepwise change in the deformation texture, highlighted by a complete disappearance of the basal texture component developed during rolling. In case of Mg-1Dy, texture changes upon annealing were less accentuated, characterized by gradual softening of the deformation basal texture with increasing annealing temperatures. The development of favorable RE-textures during annealing is believed to be a result of solute segregation to planar defects, such as grain boundaries. It was observed using atom probe tomography that Gd atoms show a much higher grain boundary segregation tendency than Dy atoms. The enhanced segregation behavior of Gd manifests during annealing into a strong growth advantage of recrystallized off-basal orientations over basal orientations originating from the deformation microstructure, continuing as discontinuous grain growth at higher annealing temperatures and longer durations. No distinctive growth advantage was witnessed during recrystallization and grain growth of Mg-1Dy. Different segregation effects between the two RE elements and the resulting annealing texture evolution strongly impacted the room temperature tensile ductilities of both alloys. Mg-1Gd seemed to exhibit concomitant precipitation hardening effects, thereby displaying higher tensile strength along with enhanced ductilities. This work demonstrates the exciting possibility of being able to selectively exploit grain boundary characteristics using RE elements as an effective mechanism to tailor the microstructure during thermomechanical processing, thereby improve the mechanical performance of Mg alloys. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.