Mechanical Properties Of Powder Metallurgy Titanium Alloys And Densification Of Titanium Powders During HIPing

In the present study, Ti-6Al-4V and Ti-5Al-2.5Sn pre-alloyed powders were used to prepare powder metallurgy (PM) titanium alloys. The powders were produced by electrode induction melting gas atomization technology (EIGA).The characterization features of the Ti-6A1-4V powder were studied. The DSC curve shows that the β transus is987℃. The martensitic is the only phase of the Ti-6A1-4V powder at atomized condition; however the martensitic can be fully resolved at850℃. Based on the effect of HIPing parameters on relative density and mechanical properties of PM Ti-6A1-4V alloys, it is shown that the optimized HIPping parameters in present work are temperature ranging from880℃to940℃and the pressure over100MPa, holding for3hours.Porosity control is very crucial for PM alloys during application. In this study porosity caused by HIPing process and capsule failure during HIPing has been accessed and re-HIPing was used to eliminate porosity defects. It can be seen that porosity can deteriorate mechanical properties of PM alloys, and re-HIPing can eliminate the porosity caused by HIPing parameters. However whether the porosity in the PM compact with capsule failure can be eliminated or not, it totally depends on the level of leak during first HIPing cycle. Analysis of Argon content is an effective tool to distinguish the capsule failure samples from the fully dense samples.The effects of hot isostatic pressing (HIPing) variables and heat treatment on the tensile properties of powder metallurgy Ti-6Al-4V alloy were investigated. It indicated that among the related parameters, capsule failure rank the first, following by cooling rate, surface state of capsule, solution temperature and annealing time, and the least important factor is the particle size distribution.Simulation of the final dimensions of shaped components under typical capsule designs was carried out based on finite element method (FEM). Several components were also produced through HIPing technique to compare with the FEM predictions. It indicated that the simulation results are in agreement with the experimental data, and the shrinkage of components always happened at the local weakness positions. Finite element method is a useful tool for container design, especially for manufacturing near-net-shape components.