Deformation mechanisms and dynamic recrystallization of AZ31 Mg alloy with different initial textures during hot tension
Deformation mechanisms and dynamic recrystallization of AZ31 Mg alloy with different initial textures during hot tension
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DOI：
10.1016/j.matdes.2013.03.028
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发表时间：
2013-09
影响因子：
8.4
通讯作者：
Nali Li;G. Huang;X. Zhong;Qing Liu
中科院分区：
文献类型：
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作者：
Nali Li;G. Huang;X. Zhong;Qing Liu
通过使用三个不同初始织构的拉伸试样，研究了 AZ31 镁合金在 300°C 温度和 5×10−4s−1 应变速率拉伸过程中的变形机制和动态再结晶（DRX）。结果表明，初始织构对AZ31的孪生行为有很大影响。 ND标本中观察到大量{10−12}延伸孪晶，ND45标本中仅观察到少量{10−12}延伸孪晶，而RD标本中未观察到孪晶。初始纹理也会影响 DRX。如果 c 轴平行于拉伸轴 (TA)，如 ND 样品所示，可以观察到广泛的 DRX 过程，并且在断裂前 45% 拉伸应变后形成最高的 DRX 体积分数和最小的晶粒尺寸。当 c 轴倾斜 45° 或垂直于 TA 时，如 ND45 或 RD 样本所示，DRX 发生速度较慢，导致与 ND 样本相比 DRX 体积分数较低。在所有样品中，具有原样ND45试样取向的未再结晶晶粒织构旋转到原样RD试样的取向，而具有原样RD试样取向的未再结晶晶粒织构演变为与TA平行的〈10−10〉基底纤维织构。人们认为，初始织构对ND试样DRX的影响是由<c+a>滑移的激活引起的，因为在拉伸过程中，横向滑移和爬升比其他滑移系统更容易发生，从而形成大角度边界。因此，通过滑移而不是通过 {10−12} 延伸孪生变形的晶粒在 DRX 产生的张力期间将无法存活。根据变形机制和 DRX 行为，讨论了三个拉伸样品的微观结构和织构的演变。
Deformation mechanisms and dynamic recrystallization (DRX) of AZ31 Mg alloy during tension at a temperature of 300°C and strain rate of 5×10−4s−1were investigated by using three tension specimens with different initial textures. It is shown that initial texture has a great influence on the twinning behavior of the AZ31. A lot of {10−12} extension twins were observed in ND specimen, and only a small amount of {10−12} extension twins were observed in ND45 specimen, while no twin was observed in RD specimen. The initial texture also affects DRX. If the c-axis is parallel to the tensile axis (TA), as seen in ND specimen, extensive DRX process was observed, and a highest volume fraction of DRX together with a smallest grain size was formed after 45% tension strain before fracture. When the c-axis is inclining 45° or perpendicular to the TA, as seen in ND45 or RD specimen, DRX occurred at a slow rate resulting with a low volume fraction of DRX compared to ND specimen. In all samples, the texture of unrecrystallized grains with the orientation of the as-received ND45 specimen rotates to that of the as-received RD specimen, while the texture of unrecrystallized grains with the orientation of the as-received RD specimen evolves into a basal fiber texture with 〈10−10〉 parallel to the TA. It is believed that the effect of initial texture on DRX of ND specimen is caused by the activation of 〈c+a〉 slip since cross-slip and climb are easier to take place than for other slip systems during tension resulting in the formation of high angle boundaries. As a consequence, the grains, which deformed by slipping, not by {10−12} extension twinning, would not survive during tension due to DRX. The evolutions of microstructures and textures of the three tensile samples were discussed based on their deformation mechanisms and DRX behavior.