一种新型Ti-Al-V-Zr-Mo-Nb低温钛合金组织与性能研究

Investigation on the Microstructure and Mechanical Properties of a Novel Ti-Al-V-Zr-Mo-Nb Cryogenic Temperature Titanium Alloy

摘要:

本文设计并制备了一种新型Ti-Al-V-Zr-Mo-Nb系近α型低温粉末钛合金CT1400,并对其进行了系统的微结构表征、低温力学性能测试以及低温变形行为分析。结果表明,CT1400主要由片层α相、等轴α相以及少量片层β相组成,由动态再结晶形成的等轴α相体积分数随成形温度的提升而增加,并体现出明显的晶体学随机取向特征。成形温度对CT1400钛合金20K极限拉伸强度影响不明显,得益于最为充分的动态再结晶过程,920℃制备的样品具有最佳的低温失效应变。此外,CT1400在20K低温条件下为一种位错滑移+孪生的混合变形行为,孪生变形可以通过协调位错滑移提升材料的低温塑性,而低温下的位错强化作用导致CT1400具有较高的极限拉伸强度,使其最终体现出优异的低温强韧性匹配。

关键词:钛合金;低温;显微组织;力学性能

Abstract:

In this work, a novel near α-type powder metallurgy Ti-Al-V-Zr-Mo-Nb titanium alloy (CT1400) was firstly designed and fabricated. The microsturcture characterization, cryogenic temperature mechanical property and deforamtion behavior were also systematically investigated. Results indicated that the CT1400 mainly consists of lamellar α, equiaxed α and a few of lamellar β. The volume fraction of equiaxed α which results from dynamic recrystallization process increases with the increasing fabrication temperature, and shows diversity crystal orientation characteristic. The fabrication temperature has no significant influence on the ultimate tensile stress of CT1400 under 20 K, however, the sample fabricated with 920 ℃ displays optimal cryogenic temperature failure strain resulting from the most sufficient dynamic recrystallization process. Furthermore, CT1400 shows a mixed dislocation slipping and twinning deformation behavior at cryogenic temperature. The twinning deformation could improve the plastic deformation capacity of CT1400 via coordinating dislocation slipping process, and the dislocation strengthening effect also induces the superior ultimate tensile stress under cryogenic temperature.

Key words:titanium alloy; cryogenic; microstructure; mechanical properties