Semenova I P, Valiev R Z, Yakushina E B, Salimgareeva G H, Lowe T C
Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, 12 K. Marx Str, Ufa, 450000 Russia.
Los Alamos National Laboratory, Los Alamos, NM 87545 USA.
J Mater Sci. 2008;43(23-24):7354-7359. doi: 10.1007/s10853-008-2984-4. Epub 2008 Dec 1.
Severe plastic deformation (SPD) of titanium creates an ultrafine-grained (UFG) microstructure which results in significantly enhanced mechanical properties, including increasing the high cycle fatigue strength. This work addresses the challenge of maintaining the high level of properties as SPD processing techniques are evolved from methods suitable for producing laboratory scale samples to methods suitable for commercial scale production of titanium semi-products. Various ways to optimize the strength and fatigue endurance limit in long-length Grade 4 titanium rod processed by equal channel angular pressing (ECAP) with subsequent thermal mechanical treatments are considered in this paper. Low-temperature annealing of rods is found to increase the fatigue limit, simultaneously enhancing UFG titanium strength and ductility. The UFG structure in titanium provides an optimum combination of properties when its microstructure includes mostly equiaxed grains with high-angle boundaries, the volume fraction of which is no less than 50%.
钛的严重塑性变形（SPD）会产生超细晶粒（UFG）微观结构，从而显著提高机械性能，包括提高高周疲劳强度。随着SPD加工技术从适用于生产实验室规模样品的方法发展到适用于钛半成品商业规模生产的方法，这项工作解决了维持高性能水平的挑战。本文考虑了通过等通道转角挤压（ECAP）及随后的热机械处理来优化长尺寸4级钛棒强度和疲劳 endurance极限的各种方法。发现棒材的低温退火会提高疲劳极限，同时增强UFG钛的强度和延展性。当钛的微观结构主要由具有高角度边界的等轴晶粒组成，且其体积分数不少于50%时，钛中的UFG结构可提供最佳的性能组合。
