The effect of Cr additions and oxidation on densification, microstructure, phase constituents and mechanical properties of TiAlCr alloys produced by SPS

Abstract

Ternary Ti-47.5Al-(1–3)Cr (at. %) and reference quaternary Ti-48Al-2Cr-2Nb (at. %) titanium aluminide alloys were processed from elemental powders utilizing mechanical milling, mechanical alloying and spark plasma sintering. The effect of Cr additions and oxidation on the densification behavior, microstructure, phase constituents and mechanical properties of the sintered alloys were investigated. The results point out that Cr additions and the presence of O play a significant role on the densification process i.e., compaction rates and sintering temperatures of the alloys. The microstructure and phase constituents of the alloys were studied based on historical experimental and theoretical data. Furthermore, the compression properties and fracture morphologies at experimental temperatures were found to be determined by a combination of response to densification, microstructural and phase evolutions effects as opposed to composition only. High additions of Cr coupled with the high level of oxidation impaired the compression properties of the ternary alloys, resulting in a 9% decrease in peak stress at higher testing temperatures. At these temperatures, the quaternary alloy showed good compression properties compared to the ternary alloys.