Effect of reinforcements on β→α transformation and tensile properties of a near α titanium matrix composite

Abstract

In this paper, the (TiB + TiC + Y2O3)/α-Ti composite were fabricated by vacuum arc melting furnace to investigate microstructure evolution and tensile properties. With reinforced with ternary reinforcement (TiB + TiC + Y2O3), αGB is almost disappeared at the prior β grain boundary and β grain size decreases by an order of magnitude. The distribution of reinforcement is homogeneous and mainly distributed at β grain boundary and α colony boundary. In general, in matrix, αGB is preferred to simultaneously maintain Burgers orientation relationship with two adjacent β grains. However, in (TiB + TiC + Y2O3)/α-Ti composite, αs direct precipitates in β grain and grows in more equiaxed-like without forming αGB at grain boundary because of the constitutional undercooling and heterogeneous nucleation caused by (TiB + TiC + Y2O3), thus promotes the formation of non-Burgers related α grain which weaken α texture at last. In addition, the composite shows incredible performance at 973 K that achieved both high strength and ductility. The strengthening mechanism has also been discussed informally.