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Thermal Stability of an Mg‐Nd Alloy Processed by High‐Pressure Torsion
Advanced Engineering Materials ( IF 3.4 ) Pub Date : 2019-09-26 , DOI: 10.1002/adem.201900801
Samia Tighiouaret 1 , Rabeb Lachhab 2 , Abdelkader Hanna 1 , Hiba Azzeddine 1 , Yi Huang 3, 4 , Thierry Baudin 5 , Anne-Laure Helbert 5 , François Brisset 5 , Djamel Bradai 6 , Terence G. Langdon 4
Affiliation  

The evolution of microstructure, texture and mechanical properties of an Mg‐1.43Nd (wt.%) alloy are investigated after processing by high‐pressure torsion at room temperature through 5 turns and isochronal annealing for 1 h at 150, 250, 350 and 450 °C using Electron BackScatter Diffraction and Vickers microhardness. The alloy exhibits a good thermal stability up to an annealing at 250 °C, with mean grain size of ≈0.65 μm. The microhardness shows an initial hardening after annealing at 150 °C and then a subsequent softening. The deformation texture, a basal texture shifted 60° away from the shear direction (SD), is retained during annealing up to 250 °C. By contrast, a basal texture with symmetrical splitting towards SD is developed after annealing at 350 °C. The precipitation sequence and their pinning effect are responsible for the age‐hardening, stabilization of grain size and the texture modification. The kinetics of grain growth in the Mg‐1.43Nd alloy follows two stages depending on the temperature annealing range, with an activation energy of ≈26 kJ/mol in the low temperature range of 150–250 °C and ~147 kJ/mol in the high temperature range of 250–450 °C.

中文翻译:

高压扭转加工的 Mg-Nd 合金的热稳定性

研究了 Mg-1.43Nd (wt.%) 合金在室温高压扭转 5 圈并在 150、250、350 和 450 下等时退火 1 小时后组织、织构和力学性能的演变°C 使用电子背散射衍射和维氏显微硬度。该合金在 250 °C 下退火后表现出良好的热稳定性,平均晶粒尺寸约为 0.65 μm。显微硬度显示在 150 °C 退火后初始硬化,然后软化。变形织构,即偏离剪切方向 (SD) 60° 的基础织构,在高达 250 °C 的退火过程中得以保留。相比之下,在 350 °C 退火后,会形成向 SD 对称分裂的基底织构。析出序列及其钉扎效应是时效硬化的原因,晶粒尺寸的稳定和织构的改变。根据退火温度范围,Mg-1.43Nd 合金的晶粒生长动力学遵循两个阶段,在 150-250 °C 的低温范围内活化能为 ≈26 kJ/mol,在 150-250 °C 的低温范围内活化能约为 147 kJ/mol。 250–450 °C 的高温范围。
更新日期:2019-09-26
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