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/s11661-002-1016-2
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发表时间：
2002-03-01
影响因子：
2.8
通讯作者：
Paton, NE
中科院分区：
文献类型：
--
作者：
Williams, JC;Baggerly, RG;Paton, NE
含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柱面上取向滑移或沿沿着c轴平行加载以实施非基面变形模式。大多数试验是在压缩和77至1000 K之间的温度下进行的。预抛光表面的痕量分析，使识别的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，可以抑制二次孪晶和滑移系，从而增加具有最高分解应力的单滑移系的应变调节趋势。在晶体取向的基础滑移，从孪生多滑移，最后，到基础滑移的转变发生在较低的Al含量的合金，而Ti-6.6% Al，只有基础滑移在所有温度下测试观察到的温度增加。作为Al含量的函数的基底滑移和棱柱滑移的临界分辨剪切应力（CRSS）值的比较表明，棱柱滑移在室温下在纯Ti中是有利的，但在Ti-6.6%Al晶体中，激活这两个系统的应力在很宽的温度范围内变得基本相等。轴显示出广泛的孪晶在较低的Al浓度和滑移在较高的Al浓度，与滑移和孪晶在中间组合物的混合物。一些测试也是在拉力下进行的，载荷平行于c轴。在这些情况下，观察到孪生，并解决剪切塑性变形的孪生是低得多，在压缩加载中观察到的滑移。
Single crystals of Ti-Al alloys containing 1.4, 2.9, 5, and 6.6 pct Al (by weight) were oriented for slip on either basal or prism planes or loaded parallel along the c-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, AI 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 the c-axis showed extensive twinning in lower Al concentrations and slip at higher Al concentrations, with a mixture of slip and twinning at intermediate compositions. A few tests also were conducted in tension, with the load applied parallel to the c-axis. In these cases, twinning was observed, and the resolved shear for plastic deformation by twinning was much lower that that for slip observed in compression loading.