Microstructural and texture changes during equal channel angular pressing of an Al–Mg–Sc alloy
Microstructural and texture changes during equal channel angular pressing of an Al–Mg–Sc alloy
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DOI：
10.1016/j.jallcom.2015.06.029
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发表时间：
2015-11
影响因子：
6.2
通讯作者：
O. Sitdikov;E. Avtokratova;T. Sakai
中科院分区：
文献类型：
--
作者：
O. Sitdikov;E. Avtokratova;T. Sakai
研究了Al-Mg-Sc合金在200℃等通道角挤压（ECAP）过程中组织和显微组织的演变。当ECAP应变值为1 < ε < 4时，随着应变的增大，合金的显微硬度逐渐饱和，并迅速硬化。应变到ε≤4时，在细观水平上没有引起明显的结构变化，如原始晶粒主要沿剪切方向旋转，遵循简单的剪切变形模式。织构变化的特点是产生了相对较强的双相织构，这是fcc金属传统高应变轴对称变形的典型特征，即<100>和<111>方向平行于压制方向（PD）。而当ECAP应变大于4时，组织和织构都发生了显著变化。这主要与在不同方向上频繁形成微剪切带有关，导致局部晶格向<110>方向旋转，并在高应变下频繁形成新的超细晶粒形核。在ε = 12的最高应变下，合金中形成了高角晶界约占40 ~ 45%的超细晶组织，且织构在PD中取向的最大值接近<110>。
Evolution of the microstructure and microtexture of an Al–Mg–Sc alloy during equal channel angular pressing (ECAP) at 200 °C was studied. Increasing the ECAP strain of 1 < ε < 4 was accompanied by a rapid hardening followed by a saturation of microhardness at the higher strains. Straining to ε ≤ 4 did not result in any significant structural changes on a mesoscopic level: e.g. the original grains were mainly rotated toward the shearing direction in accordance with the simple shear deformation mode. At that, the texture changes were characterized by creation of a relatively strong duplex texture, typical for conventional high-strain axi-symmetric deformation of fcc metals, i.e. the directions of <100> and <111> were oriented parallel to the pressing direction (PD). At ECAP strains larger than 4, in contrast, significant changes took place in both the microstructure and the texture evolved. Those were mainly related to the frequent formation of microshear bands developed in various directions, that resulted in the local lattice rotations toward <110> and frequent nucleation of new ultrafine grains at high strains. Ultrafine crystallite structures were formed in the alloy characterized by the fraction of high-angle boundaries of about 40–45% and a texture with the near <110> maximum oriented in PD at the highest strain of ε = 12.