Dynamic tensile properties of Ti-47Al-2Mn-2Nb-0.8TiB2 alloy

Room temperature tensile properties of Ti-47Al-2Mn-2Nb-0.8TiB(2) alloy with nearly lamellar (NL) microstructures were investigated between the strain rates 10(-5) and 10(-1)s(-1) using a conventional testing machine, and between the strain rates 20 and 10(3)s(-1) using a self-designed Split-Hopkinson tensile bar setup with a rotating disk. It was found that tensile ductility fluctuates within a narrow range with the variation of the strain rate: dynamic elongation approximates to static elongation. But dynamic strengths sigma(d) of the alloy are obviously higher than static strengths sigma(s); there exists linear relationship between sigma(s) and the logarithm of the strain rate (sigma(s)=A+Bln (epsilon) over dot), and between dynamic strength sigma(d) and the strain rate (sigma(d)=C+D (epsilon) over dot). Fractographic analysis indicated that the alloy fractures in a mixed mode of predominant transgranular cleavage and minor intergranular cracking under static and dynamic strain rates. Environmental effect is excluded from a main cause for the room-temperature brittleness of the investigated alloy.