Microstructure, Microsegregation, and Mechanical Properties of Directional Solidified Mg–3.0Nd–1.5Gd Alloy
Microstructure, Microsegregation, and Mechanical Properties of Directional Solidified Mg–3.0Nd–1.5Gd Alloy
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DOI：
10.1007/s40195-014-0151-2
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发表时间：
2014-10
期刊：
影响因子：
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通讯作者：
Shaojun Liu;Guangyu Yang;W. Jie
中科院分区：
文献类型：
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作者：
Shaojun Liu;Guangyu Yang;W. Jie
研究了Mg-3.0Nd-1.5Gd三元合金定向凝固组织、显微偏析和力学性能。结果表明，凝固组织由枝晶初生α（Mg）相、枝晶间α（Mg）+Mg 12（Nd，Gd）共晶和Mg 5Gd相组成。在温度梯度为40 K/mm，冷却速率为0.4 ~ 4 K/s范围内，一次枝晶间距λ 1和二次枝晶间距λ 2与冷却速率R的关系式分别为λ1= 8.0415 × 10 − 6 R − 0.279和λ2= 6.8883 × 10− 6 R −0.205。由于忽略了溶质Nd和Gd在α（Mg）基体中的反扩散，Scheil模型计算的Nd和Gd元素浓度分布与EPMA测量的结果有不同程度的偏差。Gd的显微偏析比Nd的显微偏析更依赖于生长速率。定向凝固合金的强度高于非定向凝固合金，且随着生长速率的增加，定向凝固合金的抗拉强度提高，而相应的延伸率降低。
The microstructure, microsegregation, and mechanical properties of directional solidified Mg–3.0Nd–1.5Gd ternary alloys were experimentally studied. Experimental results showed that the solidification microstructure was composed of dendrite primary α(Mg) phase and interdendritic α(Mg) + Mg12(Nd, Gd) eutectic and Mg5Gd phase. The primary dendrite arm spacingλ1and secondary dendrite arm spacingλ2were found to be depended on the cooling rateRin the formλ1= 8.0415 × 10−6R−0.279andλ2= 6.8883 × 10−6R−0.205, respectively, under the constant temperature gradient of 40 K/mm and in the region of cooling rates from 0.4 to 4 K/s. The concentration profiles of Nd and Gd elements calculated by Scheil model were found to be deviated from the ones measured by EPMA to varying degrees, due to ignorance of the back diffusion of the solutes Nd and Gd within α(Mg) matrix. And microsegregation of Gd depended more on the growth rate, compared with Nd microsegregation. The directionally solidified experimental alloy exhibited higher strength than the non-directionally solidified alloy, and the tensile strength of the directionally solidified experimental alloy was improved, while the corresponding elongation decreased with the increase of growth rate.