Fracture toughness of multiphase TiAl-Nb alloy in situ consolidated by spark plasma sintering

Abstract

A fine-grained TiAl alloy with a composition of Ti-45Al-5Nb-1.5Cr-0.2W (mole fraction, %) with multiphases was prepared by spark plasma sintering (SPS) and heat-treating at 1 100 °C for 48 h. The relationship among sintering temperature, microstructure and fracture toughness were investigated by X-ray diffractometry (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and mechanical testing. The results show that microstructure of the bulk alloy depends on the sintering temperature strongly, and the main phase TiAl and few phases Ti₃Al and niobium solid solution (Nbss) are observed in the SPS bulk samples. In the heat-treatment condition, the lamellar and Nbss phase can provide significant toughening by plastic strengthening, interface decohension, crack branch and crack bridge mechanisms. The fracture mode of the SPS TiAl composite samples is intergranular rupture and cleavage fracture.

Keywords

TiAl-Nb alloy / spark plasma sintering / fracture toughness / microstructure

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