On the microstructure and mechanical property of as-extruded Mg-Gd-Y-Zn alloy with Sr addition

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• 作者：Shengming Liu^a ; ^{lsmxmh@163.com" class="auth_mail" title="E-mail the corresponding author} ; Hui Diao^b ; Linjiang Chai^c ; Bo Song^d ; ^{bosong@swu.edu.cn" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Mg alloys ; LPSO ; Sr ; Bimodal grains ; Mechanical property
• 刊名：Materials Science & Engineering A
• 出版年：2017
• 出版时间：2 January 2017
• 年：2017
• 卷：679
• 期：Complete
• 页码：183-192
• 全文大小：3087 K

文摘

In this study, microstructure evolutions of Mg-6Gd-3Y-0.1Zn-xSr (x=0, 0.2, 0.6) alloys (named as sample 0Sr, 0.2Sr, 0.6Sr) during heat-treatment and extrusion were investigated. As-cast sample 0Sr contains typical long period stacking ordered (LPSO) phases and Mg₃RE. With Sr addition, amounts of LPSO phases decrease and are gradually replaced by the Mg₁₇Sr₂ phases. After homogenization and annealing treatment, profuse strip LPSO phases readily precipitate in grain interiors of sample 0Sr, while only Mg₁₇Sr₂ and Mg₃RE phases are detected in samples 0.2Sr and 0.6Sr. It suggests that the Sr addition would inhibit LPSO phases. After extrusion, the bimodal grain structures, the bulk and strip LPSO phases are detected in sample 0Sr, which can contribute to providing strengthening and extra strain hardening. In as-extruded sample 0.2Sr, finer recrystallized grain size, bulk Mg₁₇Sr₂ and LPSO phases (micron-scale) and Mg₅RE phase (nano-scale) are found due to the pre-annealing treatment. However, lower amounts of both nano-sized and macro-sized LPSO phases lead to the low ultimate strength (300 MPa). In sample 0.6Sr, the strip LPSO phases are readily formed even though the length and total amounts of LPSO phases decrease. More bulk Mg₁₇Sr₂ phases and LPSO phases are also precipitated, which lead to the more superior yield and ultimate strengths of 0.6Sr sample under higher temperature, as compared with the 0Sr sample.