The mechanism for the high dependence of the Hall-Petch slope for twinning/slip on texture in Mg alloys
The mechanism for the high dependence of the Hall-Petch slope for twinning/slip on texture in Mg alloys
复制标题
镁合金中孪晶/滑移霍尔-佩奇斜率高度依赖于织构的机制
DOI：
10.1016/j.actamat.2017.02.044
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发表时间：
2017
期刊：
影响因子：
9.4
通讯作者：
Qing Liu
中科院分区：
文献类型：
--
作者：
Huihui Yu;Changzheng Li;Yunchang Xin;Adrien Chapuis;Xiaoxu Huang;Qing Liu
如在镁合金中广泛报道的，随织构高度变化的Hall-Petch斜率（k）最终与变形模式的变化有关。本文采用AZ 31轧制板材（[0002]//ND）和挤压棒材（[0002]取向艾德以及艾德周围的随机分布）系统地研究了不同（0002）分布对孪晶和滑移k值的影响。ND和艾德分别指板的法线方向和杆的挤出方向。发现k对（0002）分布有很大的依赖性，即板中{10 1 <$2}孪晶的k（219 MPa μ m1/2）远低于棒中的k（435 MPa μ m1/2），而板中滑移的k（437 MPa μ m1/2）远高于棒中的k（235 MPa μ m1/2）。复合使用Schmid因子（ΔSF）和几何相容因子（m′）的差异定量地解释了这种取向对k的影响。ΔSF与激活相邻晶粒中的滑移/孪生所需的额外应力有关，而m′反映了相邻晶粒中滑移/孪生开始时的应力集中效率。棒中孪晶的m′相对于板中孪晶的m′较低，这主要解释了棒中孪晶的k较高。在拉伸过程中，板状结构的基极偏离理想织构的倾角比棒状结构的大得多，这导致了更高的基滑移活动。由此产生的从一个晶粒中的基底滑移到相邻晶粒中的棱柱滑移的高比例滑移转移大大地放大了ΔSF并减小了m′，这两者都产生了板中比杆中更高的滑移k。计算了不同变形传递方式下晶体学取向与m′的关系，揭示了决定m′的主要因素。
A Hall-Petch slope (k) that is highly changeable with texture, as extensively reported in Mg alloys, is ultimately related to the variation of deformation modes. In this paper, the influence of different (0002) distributions on k for twinning and slip was systematically studied using an AZ31 rolled plate ([0002]//ND) and extruded rod ([0002]⊥ ED together with a random distribution around the ED). The ND and ED refer to the normal direction of the plate and extrusion direction of the rod, respectively. A high dependency of k on the (0002) distribution is found, namely, a much lower k for {10 1¯ 2} twinning in the plate (219 MPa μm 1/2) than that in the rod (435 MPa μm 1/2), but a much higher k for slip in the plate (437 MPa μm 1/2) than that in the rod (235 MPa μm 1/2). Compound use of the difference in Schmid factor (ΔSF) and geometric compatibility factor (m′) quantitatively explains this orientation effect on k. ΔSF relates to the extra stress needed for the activation of slip/twinning in a neighboring grain, and m′ reflects the efficiency of the stress concentration at the onset of slip/twinning in an adjacent grain. The lower m′ for twinning in the rod versus the plate primarily accounts for the higher k for twinning in the rod. A much larger inclination of basal poles away from the ideal texture exists in the plate than in the rod, which induces a higher activity of basal slip during tension. The resultant high fraction of slip transfer from basal slip in one grain to prismatic slip in the neighboring grain largely amplifies ΔSF and reduces m′, both of which yield a higher k for slip in the plate than in the rod. The relationship between the crystallographic orientation and m′ was also calculated for different types of deformation transfer, and the main factor that determines m′ was revealed.