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Creep behaviour of polycrystalline intermetallic Ti-53.4mol.%Al

1989; Elsevier BV; Volume: 114; Linguagem: Inglês

10.1016/0921-5093(89)90840-x

1873-4936

Tohru Takahashi, Hashiru Nagai, Hiroshi Oikawa,

Microstructure and mechanical properties

Creep behaviour under a constant compressive stress of 80 to about 400 MPa was investigated at 950 to about 1200 K on the polycrystalline intermetallic compound Ti-53.4mol.%Al, whose average grain diameter was 42 μm. The shape of the creep curves depended significantly on the test conditions. At high stresses an extensive normal primary stage, followed by a broad steady-state creep region, was observed. The extent of the normal primary stage diminished gradually with decreasing stress and, eventually, accelerating creep prevailed at low stresses. The stress and temperature dependence of the creep rates were greatly affected by the strain. The stress exponent n and the apparent activation energy Q, which were high in the early stages of deformation, decreased with increasing strain and reached their plateau values at about 0.3 true strain: n0.3 ∼ 4 aand Q0.3 ∼ 320 kJ mol−1. A transition was observed in n and Q for minimum creep rates which were attained at various strain depending on the creep condition. In the high-stress region nm ∼ 4.5 and Qm ∼ 360 kJ mol−1, whereas they were almost twice these values in the low-stress region.