intermetallics, thermo-mechanical processing, microstructure, scanning electron microscopy (SEM), XRD spectra, micro-hardness test

Abstract

The formation of a high quality as-cast structure for the Ti-46Al-6.5Nb-0.5Ta-1Cr-0.3Ni--0.2Si (at.%) alloy, with a new alloying concept, and also the application of a thermomechanical (TM) processing scheme was the subject of present investigation. The investigations consisted of structural and mechanical characterizations of the alloy in 6 different structural conditions: S1 -in cast state, S2 -after a heat treatment of homogenization, S3-S6 -after a TM processing scheme. The micro-structural investigations were performed using a SEM analyzing system, and an X-ray diffractometer. The investigations of mechanical properties have been based on tensile strength, modulus of elasticity, elongation to fracture measurements and fracture surface analysis for the as-cast sample, and on micro-hardness measurements for the TM processed samples. The alloy in cast condition, with specific nearlamellar morphology, has a homogeneous, fine-grained structure (d ∼ 30 µm), and no axial texture. Thus, a grain refinement of new proposed alloy was achieved. For the TM processed specimens, the micro-hardness measurements have revealed a proper concordance between HV values and micro-structural evolution of the samples, being argued and analyzed after each TM processing step. The presented results can underline that the new proposed alloy can be TM processed around 1200 • C, starting from an optimized as-cast structure. K e y w o r d s : intermetallics, thermo-mechanical processing, microstructure, scanning electron microscopy (SEM), XRD spectra, micro-hardness test