Powder Metallurgy Ti-6Al-4V Alloy with Wrought-like Microstructure and Mechanical Properties by Hydrogen Sintering

Titanium powder is typically sintered in high vacuum to achieve high density and low oxygen. Sintered materials usually have coarse grain size and lamellar structure in the case of sintered Ti-6Al-4V alloys. In this work, a novel process is designed to take advantage of both the higher sintered density for using TiH2 as raw material and the phase transformation induced by hydrogen that produces fine grain sizes. The process can produce near-fully dense (>99%Ti-6Al-4V) Ti materials with very fine grain size (~<1.0µm) in as-sintered state. The refined microstructure has advantages over coarse lamellar structure of conventional sintered Ti materials from the stand point of mechanical properties. The as-sintered Ti-6Al-4V can also be heat treated to obtain wrought-like microstructure and mechanical properties. This presents a new opportunity for low cost manufacturing of PM Ti materials with both static and fatigue mechanical properties equivalent to that of wrought Ti materials. This presentation will show the results of microstructure and mechanical properties of as-sintered, heat treated, and those with an additional gaseous-isostatic-forging-treatment (GIFT) processing. The results demonstrates that PM Ti-6Al-4V can be made to have equivalent mechancial, including fatigure, properties to that of wrough Ti.