Influence of grain size, aging conditions and tension rate on the mechanical behavior of titanium low-cost metastable beta-alloy in thermally hardened condition

Taking titanium low-cost metastable β alloy TIMETAL-LCB (Ti-1.5(wt.%)Al-4.5Fe-6.8Mo) as a program material, the influence of grain size, size of secondary α-phase precipitates after aging, and strain rate (in the range of 1.6×10−4-7.3×10−2 s−1) on mechanical behavior was studied. Aging caused increase in strength and decrease in ductility parameters as compared to initial single-phase metastable (as-quenched) β condition with two different β grain sizes (Coarse Grained, CG, 200 μm and Fine Grained, FG, 20 μm), and these effects were more pronounced at higher strain rates. Aged FG conditions had essentially higher resource of ductility compared to CG ones after the same aging regimes. Obtained results are discussed in terms of mechanical properties changes induced by aging with respect to initial as-quenched condition. Analysis of area under the engineering stress-strain curves, characterizing the work expended on deformation until fracture and representing tensile toughness of the material, showed that it decreased after aging at all strain rates applied, with essential superiority of FG conditions over CG.