Deformation behavior of HCP Ti-Al alloy single crystals
Deformation behavior of HCP Ti-Al alloy single crystals
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DOI：
10.1007/s11661-002-0153-y
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
J. Williams;R. G. Baggerly;N. Paton
中科院分区：
文献类型：
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作者：
J. Williams;R. G. Baggerly;N. Paton
含有1.4、2.9、5和6.6% Al（按重量计）的Ti-Al合金单晶在基面或棱镜面上取向小于1 >滑移，或沿轴平行加载以强制非基面变形模式。大多数试验是在压缩条件下进行的，温度在77至1000 K之间。预抛光表面的痕量分析使识别孪生或滑移系统主要负责变形。提高变形温度、Al含量或两者都能抑制二次孪晶和滑移体系，从而增加具有最高分解应力的单滑移体系的应变调节倾向。在基底滑移取向的晶体中，随着温度的升高，低Al含量合金从孪晶转变为多重滑移，并最终转变为基底滑移，而对于ti - 6.6% Al，在所有温度测试中都只观察到基底滑移。比较了基滑移和棱镜滑移的临界分解剪切应力（CRSS）值与Al含量的关系，结果表明，纯Ti在室温下有利于棱镜滑移，但在Ti- 6.6% Al晶体中，在很宽的温度范围内，激活这两个系统的应力基本相等。对定向晶体进行压缩测试，使载荷与轴平行施加，结果表明，在较低的Al浓度下存在广泛的孪晶，在较高的Al浓度下存在<c+a>滑移，在中等成分下存在<c+a>滑移和孪晶的混合物。一些试验也进行了拉伸，与平行施加载荷轴。在这些情况下，观察到孪晶，并且由孪晶引起的塑性变形的分辨剪切远低于在压缩加载中观察到的<c+a>滑移。
Single crystals of Ti-Al alloys containing 1.4, 2.9, 5, and 6.6 pct Al (by weight) were oriented for <a> slip on either basal or prism planes or loaded parallel along thec-axis to enforce a nonbasal deformation mode. Most of the tests were conducted in compression and at temperatures between 77 and 1000 K. Trace analysis of prepolished surfaces enabled identification of the twin or slip systems primarily responsible for deformation. Increasing the deformation temperature, Al content, or both, acted to inhibit secondary twin and slip systems, thereby increasing the tendency toward strain accommodation by a single slip system having the highest resolved stress. In the crystals oriented for basal slip, transitions from twinning to multiple slip and, finally, to basal slip occurred with increasing temperature in the lower-Al-content alloys, whereas for Ti-6.6 pct Al, only basal slip was observed at all temperatures tested. A comparison of the critically resolved shear stress (CRSS) values for basal and prism slip as a function of Al content shows that prism slip is favored at room temperature in pure Ti, but the stress to activate these two systems becomes essentially equal in the Ti-6.6 pct Al crystals over a wide range of temperatures.Compression tests on crystals oriented so that the load was applied parallel to thec-axis showed extensive twinning in lower Al concentrations and <c+a> slip at higher Al concentrations, with a mixture of <c+a> slip and twinning at intermediate compositions. A few tests also were conducted in tension, with the load applied parallel to thec-axis. In these cases, twinning was observed, and the resolved shear for plastic deformation by twinning was much lower that that for <c+a> slip observed in compression loading.