TENSILE DEFORMATION OF THE FORGED L1(2) COMPOUND AL66TI25MN9

The L1(2) compound Al66Ti25Mn9 was induction-melted, cast, homogenized and successfully isothermally forged. Cylindrical 'buttonhead' tensile specimens were machined from the plane of the forging and tested in the temperature range 298-1073 K at a strain rate of approximately 5 x 10(-5)s-1. The 0.2% offset yield in tension remained essentially constant up to 623 K and then underwent a discontinuous drop. Further increases in temperature caused a steady gradual decrease in strength. Serrated flow was observed in the load-displacement curves over the temperature range 623-923 K. A small (0.2%) but finite plastic elongation was measured at ambient which gradually increased to 1.3% at 623 K. Further increase in temperature caused a sharp decrease in ductility with a minimum at 773 K. Fracture mode transitioned gradually from transgranular cleavage to intergranular failure, although the onset of intergranular failure was coincident with neither the ductility minimum nor the drop in yield strength. The deformed specimens were examined in a transmission electron microscope in an attempt to explain these observations.