The research of technological properties titanium alloy Ti-6Al-4V. Part 1. The microstructure and mechanical properties

摘要

The paper describes the results of comprehensive studies of the microstructure, mechanical and technological properties (formability and weldability in the solid state) of the titanium sheet alloy VT6 (Ti-6Al-4V) with improved superplastic properties produced by PSC «VSMPO?AVISMA». The first part is investigated the initial microstructure of the alloy and its mechanical properties over a wide temperature range from 650 to 900ºC at strain rates of 4×10-4, 4×10-3 4×10-2 s-1. It is found that the initial microstructure of a sheet is uniform, ultrafine grains have an average size of 1.2 microns. The initial grain size of the microstructure is found to be from 0.1 to 4 microns. Most of the grains have a size of 0.5 to 1.5 microns. Mechanical tensile tests revealed that the ultrafine grained titanium alloy has higher superplasticity characteristics as compared with the standard VT6 sheet. The microstructure of deformed samples and data on changes in the grain size depending on the temperature and strain rate are investigated. Comparing the superplastic characteristics of the samples cut along and across to the direction of rolling indicates the absence of anisotropy. The studied alloy exhibits the best superplastic properties at temperatures from 700 to 850ºC and strain rates of 4×10-4 ? 4×10-3 s-1, which corresponds to the manifestation of the low temperature superplasticity. Relative elongation at that is from 650 to 1075%, which allow recommending the development of the studied alloy for low temperature processes of superplastic forming and diffusion welding for aerospace products.