Effect of texture and slip mode on the anisotropy of plastic flow and flow softening during hot working of Ti-6Al-4V
Effect of texture and slip mode on the anisotropy of plastic flow and flow softening during hot working of Ti-6Al-4V
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DOI：
10.1007/s11661-001-0155-1
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发表时间：
2001-07-01
影响因子：
2.8
通讯作者：
Bieler, TR
中科院分区：
文献类型：
--
作者：
Semiatin, SL;Bieler, TR
通过对从热轧板上以不同方向（轧制方向（RD）、横向（TD）、45 °和法线）切割的试样进行等温、恒应变率、热压缩试验，确定了晶体织构和滑移模式对具有群体或球形α微观结构的Ti-6Al-4V塑性流动的影响。使用固定的应变速率（0.1 s（-1））和低于β转变的各种温度进行测试。流动曲线;来自所有实验的样品分别表现出峰值流动应力，随后对于殖民地和球状微结构，出现大量和少量的流动软化。对于给定的微观结构和试验温度，虽然流动软化响应并不明显地依赖于试验方向，但是峰值流动应力和试样椭圆度的发展确实依赖于试验方向。这种取向依赖性解释使用下限（等应力型）和上限（等应变，泰勒/Bishop-Hill）模型推导出的α阶段的操作滑移系统。这些分析表明，在热加工温度下，棱柱[a]和基底[a]滑移比锥体[c + a]或[a]滑移容易得多。殖民地和球状α微观结构的流动曲线的比较表明，通过α/β界面的滑移转移和Hall-Fetch边界强化的损失可以解释热加工过程中观察到的流动软化的很大一部分。
The effect of crystallographic texture and slip mode on the plastic flow of Ti-6Al-4V with either a colony- or globular-alpha microstructure was determined by conducting isothermal, constant-strain-rate, hot-compression tests on specimens cut at various orientations (rolling direction (RD), transverse direction (TD), 45 deg, and normal) from hot-rolled plate. Testing was performed using a fixed strain rate (0.1 s(-1)) and various temperatures below the beta transus. The flow cur;es from all of the experiments exhibited a peak flow stress followed by a large and a small amount of flow softening for the colony and globular microstructures, respectively. Although the flow softening response did not depend noticeably on test direction for a given microstructure and test temperature, the peak flow stress and development of sample ovality did. This orientation dependence was interpreted using both lower-bound (isostress-type) and upper-bound (isostrain, Taylor/Bishop-Hill) models to deduce the operative slip systems in the alpha phase. These analyses suggested that prism [a] and basal [a] slip are considerably easier than pyramidal [c + a] or [a] slip at hot-working temperatures. A comparison of the flow curves for the colony and globular alpha microstructures suggested that slip transfer across alpha/beta interfaces and loss of Hall-Fetch boundary strengthening can account for a substantial portion of the flow softening observed during hot working.