Tension-compression asymmetry of extruded Mg-Gd-Y-Zr alloy with a bimodal microstructure studied by in-situ synchrotron diffraction
Tension-compression asymmetry of extruded Mg-Gd-Y-Zr alloy with a bimodal microstructure studied by in-situ synchrotron diffraction
复制标题
原位同步加速器衍射研究双峰显微组织Mg-Gd-Y-Zr挤压合金的拉压不对称性
DOI：
10.1016/j.matdes.2019.107705
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发表时间：
2019
影响因子：
8.4
通讯作者：
Zheng M Y
中科院分区：
文献类型：
--
作者：
Chi Y Q;Zhou X H;Qiao X G;Brokmeier H G;Zheng M Y
在这项工作中，拉伸-压缩不对称挤压Mg-8.4wt. %，Gd-2.3wt. % Y-0.2wt. %采用同步辐射衍射原位测试和显微组织分析方法，研究了Zr合金的双态组织结构，即弥散强化后的细晶和未弥散强化后的粗晶。结果发现，挤压合金具有良好的拉伸-压缩屈服对称性，这是由于相同的变形机制（棱柱和基底滑移）的拉伸和压缩屈服。然而，在拉伸和压缩下的宏观屈服后的应变硬化响应是不同的，因为拉伸孪晶，这主要发生在unDRX晶粒，使压缩下的变形，但不是在拉伸下的重要贡献。该合金在压缩屈服后表现出一定程度的线性应变硬化，这主要是由于拉伸孪晶的抑制和棱柱滑移的增强。拉伸孪晶的抑制主要是由于高浓度的稀土溶质元素，弱织构和晶粒细化的DRXed区域。研究表明，稀土元素的加入和晶粒细化可以有效地降低镁合金的拉压不对称性。
In this work, the tension-compression asymmetry of an extruded Mg-8.4wt.%Gd-2.3wt.%Y-0.2wt.%Zr alloy with a bimodal microstructure, consisting of fine DRXed grains and coarse unDRXed grains, was investigated by in-situ synchrotron diffraction testing and microstructure analysis. It is found that the as-extruded alloy exhibits good tension-compression yielding symmetry, which is attributed to the same deformation mechanisms (prismatic and basal slip) governing the tensile and compressive yielding. However, the strain hardening response after the macroscopic yielding is different under tension and compression, since tensile twinning, which mainly occurs in the unDRXed grains, makes an important contribution to the deformation under compression, but not under tension. The alloy shows a somewhat linear strain hardening after yielding under compression, which is mainly due to the inhibition of tensile twinning and enhancement of prismatic slip. The suppression of tensile twinning mainly results from the high concentration of rare earth solute elements, weak texture and grain refinement of the DRXed regions. This work suggests that the tension-compression asymmetry of Mg alloys can be effectively reduced by the addition of rare earth elements and grain refinement.