HIGH-TEMPERATURE DEFORMATION AND FAILURE OF AN ORTHORHOMBIC TITANIUM ALUMINIDE SHEET MATERIAL

The high-temperature deformation and failure behavior of an orthorhomb ic titanium aluminide sheet alloy (fabricated by diffusion bonding of six thin foils) was established by conducting uniaxial tension and pla ne-strain compression tests at 980 degrees C and strain rates between 10(-4) and 10(-2) s(-1). The stress-strain response was characterized by a peak stress at low strains followed by moderate flow softening. V alues of the strain-rate sensitivity index (m) were between 0.10 and 0 .32, and the plastic anisotropy parameter (R) was of the order of 0.6 to 1.0. Cavity nucleation and growth were observed during tensile defo rmation at strain rates of 10(-3) s(-1) and higher. However, the combi ned effects of low m, low cavity growth rate eta, and flow softening w ere deduced to be the source of failure controlled by necking and flow localization rather than cavitation-induced fracture prior to necking .