工业纯钛板材在冷轧和退火过程中的显微组织与织构演变（英文）

研究了工业纯钛板材在冷轧和退火过程中的显微组织与织构演变。电子背散射衍射结果表明,在冷轧条件下的塑性变形由孪生和滑移共同协调作用。当压下量小于40%时,其主要的塑性变形方式为形变孪生。在轧制过程中,同时产生了{1122}<1123>压缩孪晶和{1012}<1011>拉伸孪晶;而且,沿TD方向的织构强度随变形量增加逐渐增强。在退火过程中,随着退火时间的延长,小角度晶界缓慢减少而孪晶片层快速消失,沿TD方向的织构强度逐渐减弱。当退火时间延长至60 min时,压下量20%的样品已经完全再结晶。

工业纯钛板材冷轧及退火微观组织和织构演变规律

采用先进电子背散射衍射(EBSD)技术,深入研究了冷轧工艺变化和道次间退火处理对工业纯钛板材微观组织和织构演变的影响规律。通过对比不同一次冷轧变形量样品经退火和二次冷轧加工后的EBSD取向分布图、取向差角分布图和极图得知,一次冷轧产生的孪晶对退火再结晶晶粒尺寸及晶粒取向(织构)产生重要的影响,进而又影响二次冷轧的变形组织和织构特征,使二次冷轧变形孪晶的生成受到一定程度的抑制,孪晶分数随着轧制变形量的提高呈现先升高后降低的规律,同时会降低二次冷轧组织中{0001}基面织构组分。

α-Zr在700°C下的滑移变形机制（英文）

锆合金的力学性能、耐腐蚀性能和吸氢行为与其加工过程中形成的织构密切相关。采用700℃下的压缩变形实验、EBSD 显微组织观察以及黏塑性自洽建模研究α-Zr 的高温变形行为。结果表明,当应变速率ε≤1s^-1时,孪生变形的开启量可以忽略不计。所有滑移系的应变速率敏感因子m=0.17。选取的材料参数很好地重现了力学各向异性和变形织构,通过对比实验测量与模拟计算得出的应变各向异性对材料参数进行验证。模拟研究结果表明,在高温条件下,柱面滑移是最容易开启的变形机制,而锥面<c+a>滑移最难开启,而基面滑移和锥面滑移作为比较容易开启的滑移系在变形中大量开启。

Mg-3Al-1Zn alloy deformed along different strain paths: Role of latent hardening

The mechanical properties of magnesium alloy AZ31 were investigated experimentally with visco-plastic self-consistent modeling. Tension,compression and plane strain compression(PSC) tests were performed along 3 directions of a hot rolled plate, and the material parameters input in the model were fitted with the uniaxial stress-strain curves. The critical resolved shear stress(CRSS) for tension twinning was modeled with a modified Voce hardening law first decreasing, and then increasing with strain, that could reproduce better the flow stress for twin-predominant deformation. Such CRSS evolution may better model twin nucleation, propagation and growth. Firstly simulations were carried out assuming latent hardening coefficients for slip by other slip systems equal to self-hardening. Then different heterogeneous latent hardening were used, whose values were based on dislocation dynamics simulations from the literature. This study shows that equal self and latent hardening can reproduce the stress strain curves and plastic anisotropy as well as heterogeneous mode on mode latent hardening.Discrepancies between simulations and experimental results from PSC are explained by an under-estimation of twinning for some PSC strain paths.

AZ31镁合金在以孪生主导的塑性变形中力学行为的模拟（英文）

从实验和黏塑性自洽(VPSC)模拟两个方面定量分析具有织构的AZ31镁合金中孪晶数量及其与应力-应变曲线的关系。沿着两个不同的方向进行压缩以启动{1012}拉伸或者{1011}压缩孪生。{1012}拉伸孪晶在塑性变形的初始阶段形核并且长大到完全吞并母体。当沿着法向压缩时,{1011}孪生和{1011}-{1012}二次孪生在应变量为0.05时开始启动,并且这些孪晶的数量一直增加直到材料断裂,即应变量大于0.15。当沿着横向压缩应变量为0.06时,也会启动{1011}孪生和{1011}-{1012}二次孪生,然后在已经完全发生{1012}孪生的晶粒中大量启动。应用适当的参数,VPSC模型可以准确地判断拉伸孪晶、压缩孪晶和二次孪晶的启动和流动应力以及变形织构。从模拟中可以看出,孪生和滑移具有相同的硬化参数。

Modeling strain rate sensitivity and high temperature deformation of Mg-3Al-lZn alloy

Increasing the plastic deformation temperature of Mg alloys results in higher strain rate sensitivity,easier activation of secondary slip modes,and impeded twinning.In this study,the strain rate sensitivity is estimated for each deformation mode,and visco-plastic self-consistent modeling is used to reproduce the plastic deformation behavior of an Mg-3Al-lZn O-temper plate from 150 to 450℃.Twinning and basal slip have relatively low strain rate sensitivity,whereas secondary slip modes are highly strain rate sensitive at high temperature.The texture evolution and plastic anisotropy are modeled at different temperatures and strain rates.Results show that when the strain rate sensitivity is taken into account,compared with rate independent critical resolved shear stresses,the material parameters and predictions are different.In particular,this study shows that,for hot deformation,there is a critical strain rate above which secondary slip modes predominate,and beyond which tension twinning is activated.A similar transition is expected for modes that have different strain rate sensitivity.

工业纯钛板材的轧制织构及微观组织对其孪晶和再结晶行为的依赖性

将工业纯钛(CP-Ti)板轧制至不同程度,随后进行退火以及进行20%的再轧制。通过电子背散射衍射(EBSD)对合金微观组织的变化进行表征。重新轧制后,{1122}<1123> 压缩孪晶和{1012}<1011>拉伸孪晶产生。可以观察到孪晶的层状结构,这是由变形孪晶的缠结以及二次和三次孪晶的产生引起的。平均晶粒尺寸和孪晶量之间没有简单的关联。0.5 h退火样品中的晶粒尺寸随其预变形程度的增加而显著减小。重新轧制倾向于使晶格的重新取向更接近法线方向。虽然织构变化和孪晶体积分数很小,但平行于RD方向的{1010}纤维织构仍然保留。