Effect of Strain Path in High-Pressure Torsion Process on Hardening in Commercial Purity Titanium
Effect of Strain Path in High-Pressure Torsion Process on Hardening in Commercial Purity Titanium
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DOI：
10.2320/matertrans.me200714
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发表时间：
2008
影响因子：
1.2
通讯作者：
Y. Todaka;M. Umemoto;A. Yamazaki;J. Sasaki;K. Tsuchiya
中科院分区：
文献类型：
--
作者：
Y. Todaka;M. Umemoto;A. Yamazaki;J. Sasaki;K. Tsuchiya
以工业纯钛（ti -0.03 fe - 0.030 o，质量%）为材料，研究了高压扭转（HPT）过程中应变路径对硬化的影响。在p¼5GPa的压力下，以0.2rpm的转速进行n¼10转的单调HPT （mHPT）应变后，得到的显微硬度Hv约为3.5GPa，显微组织由100 - 200nm的等轴晶组成，位错密度高，即使进一步应变和应变梯度（进一步旋转），该值也几乎没有增加。为了研究应变路径的影响，进行了循环（cHPT）和两步HPT （2sHPT）工艺。通过n¼1=2的重复变形进行chpt应变。与mHPT工艺相比，Hv快速达到饱和值（Hv 3.5GPa）。然而，最大hv值与mhpt -strain获得的值相似。在2sHPT工艺中，首先对直径为20mm的圆盘进行hpt应变变形。其次，将10mm的圆盘切割与变形圆盘的圆周接触，然后进行变形。与单调或循环hpt应变相比，获得了更高的硬度（hv3.8 gpa）。这些结果表明，多向变形（不同应变路径的变形）有助于硬化的改善。(doi: 10.2320 / matertrans。关键词：微观结构、硬化、应变路径、钛（Ti）、热生成、高压扭转（HPT）、强塑性变形（SPD）。
The effect of strain path in high-pressure torsion (HPT) process on hardening was investigated in commercial purity titanium (Ti-0.03Fe-0.03O, mass%). After monotonic HPT (mHPT) straining up to N ¼ 10 turns at a rotation speed of 0.2rpm under a pressure of P ¼ 5GPa, theobtained Vickers microhardness, Hv, was around 3.5GPa and the microstructure consisted of equiaxed grains of 100 200nm with highdislocationdensity.ThisHvvaluewashardlyincreasedevenwithfurtherstrainandstraingradient(furtherrotation).Toinvestigatetheeffectofstrain path, cyclic (cHPT) and two-steps HPT (2sHPT) processes were carried out. The cHPT-straining performed by repetitive deformation ofN ¼ 1=2. In comparison with the mHPT process, the Hv was attained rapidly to the saturated value (Hv 3.5GPa). However, the maximum Hvvalue was similar to that obtained by mHPT-straining. In the 2sHPT process, first the disk of 20mm in diameter was deformed by HPT-straining. Secondly, the disk of 10mm was cut to contact with the circumference of the deformed disk, and then it was deformed. A higherhardness (Hv 3.8GPa) was obtained than that by monotonic or cyclic HPT-straining. These results indicate that multi-directional deformations(deformations with different strain paths) contribute to the hardening improvement. [doi:10.2320/matertrans.ME200714](Received September 3, 2007; Accepted November 13, 2007; Published December 12, 2007)Keywords: microstructure, hardening, strain path, titanium (Ti), heat generation, high-pressure torsion (HPT), severe plastic deformation(SPD).