工业纯钛室温多道次ECAP变形后横截面的硬度均匀性分析

Evolution of Hardness Homogeneity on Transverse Section of Commercially Pure Titanium Processed by ECAP at Room Temperature

在室温下,采用90°模具对工业纯钛(CP-Ti)进行多道次等径弯曲通道变形(ECAP),将每个道次变形后的试样横截面抛光后进行显微硬度的测量,并利用这些结果来绘制曲线图和等高线图,分析各道次的硬度变化以及横截面硬度分布规律。研究结果表明:工业纯钛经单道次ECAP变形后,虽然在靠近试样下表面处存在硬度较小的部分,但平均硬度显著提高,而在随后的挤压道次中硬度提高的趋势越来越小。并且经过ECAP单道次挤压后,试样中心硬度值高于试样上下表面硬度值。随着挤压道次的增加,靠近试样下表面硬度较低的区域逐渐消失,试样横截面的硬度分布越来越均匀。在4道次挤压后,试样上、下表面的硬度值稍高于试样中间的硬度值,这也说明通过ECAP多道次的加工可以使试样达到更高的硬度和更加均匀的硬度分布。

Commercially pure Ti （CP-Ti） billets were processed by equal-channel angular pressing （ECAP） at room temperature for up to four passes with a mould of 90°. The Vickers microhardness was recorded on the polished cross-sectional planes of each aspressed billet and the results were plotted in the form of curves and contour maps to provide a pictorial depiction of the hardness distri- butions throughout the cross-sections. The results showed the microhardness increased significantly after the first pass although there was a region of lower hardness running in a band near the bottom surface of the billet, and then increased by very small amounts in subsequent passes. The microhardness values of center were slightly higher than those of the top and bottom surfaces after the first pass. With numbers of passes increasing, the lower hardness region near the bottom surface disappeared and the microhardness values were distributed homogeneously throughout the cross-sectional plane after four passes of ECAP. The microhardness values of center were slightly lower than those of the top and bottom surfaces. The results showed that good homogeneity might be achieved through ECAP processing after four passes of ECAP.