| The P/M consolidation of the rapidly solidified powders is an effective way to produce very fine microstructure in the hyper-peritectic Al-Ti alloys, where the grain size is less than a few microns in diameter with fine and uniform dispersion of the Al₃Ti particles. The RSP Al-Ti alloys show good high temperature strength above 300℃ mainly due to excellant thermal stability of the aluminide. In order to investigate the deformation behavior of the Al-Ti alloy at high temperatures, fine-grained Al-1.2wt%Ti, Al-3.6wt%Ti and Al-7wt%Ti specimens were produced through hot extrusion of the rapidly solidified powders made by gas atomization. The strain-rate(ε˚) vs. flow stress(σ) relations were obtained by the strain-rate change tests in tension at 300-500℃. It has been analysed that the deformation behavior could be represented by the (ε˚/D)=A·exp[-Q_a/(RT)]·(σ/E)^n where D and E are diffusivity and elastic modulus of pure Al, respectively. Stress exponent, n, was 8.5, and the activation energy for deformation was 163∼183kJ/㏖. this observation indicates that tensile deformation of the fine-grained RSP Al-Ti alloys is governed by dislocation slip activated by lattice diffusion of aluminum. Even though the grain size is very fine, the fine dispersion of Al₃Ti particles prevents grain boundaries from being activated at the high temperature range investigated. |
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