Evolution of microstructure and superplastic deformation mechanism in super {alpha}{sub 2} Ti{sub 3}Al base alloys
- National Sun Yat-sen Univ., Kaohsiung (Taiwan, Province of China). Inst. of Materials Science and Engineering
- Rockwell International Corp., Thousand Oaks, CA (United States). Science Center
The superplastic characteristics of a super {alpha}{sub 2} Ti{sub 3}Al based alloy were studied over the range of 900--1,000 C and 8 {times} 10{sup {minus}5} {minus} 2 {times} 10{sup {minus}3} s{sup {minus}1}. The maximum superplastic elongation of the 1 and 2 mm sheets was {approximately} 600 and 1,500%, respectively, obtained at 960 C and 2 {times} 10{sup {minus}4} s{sup {minus}1}. Based on the evolution of grain structures, texture distributions, stress-strain curves, variation of the m-, {theta}- and R{sub T}/R{sub W} values, there seems to be exhibited three stages during superplastic loading. For {var_epsilon} < 0.5, the thermally activated dislocation slip process controls the deformation, with m {approximately} 0.33 and Q{sub t}-400-500 kJ/mole. For 0.5 < {var_epsilon} < 0.8, the grains become basically equiaxed and GBS starts to play the dominant role. The m-value is around 0.5 and Q{sub t} is close to 270 kJ/mole, the latter may correspond to the Ti diffusion in disordered {beta} grains or the interface diffusion. For {var_epsilon} > 0.8, the same GBS and associated accommodation mechanisms continuously operate, with strain softening or hardening occurring under different conditions. It is considered that at high temperatures the ordered {alpha}{sub 2} grains act as the rigid species and slide and rotate more freely within the {beta} matrix. The disordered {beta} grains are more likely the ones that carry accommodation through dislocation slip and climb.
- OSTI ID:
- 616192
- Journal Information:
- Acta Materialia, Journal Name: Acta Materialia Journal Issue: 2 Vol. 46; ISSN 1359-6454; ISSN ACMAFD
- Country of Publication:
- United States
- Language:
- English
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