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Room-temperature environmental embrittlement in a TiAl alloy

1992; Pergamon Press; Volume: 27; Issue: 5 Linguagem: Inglês

10.1016/0956-716x(92)90347-h

1873-2712

C.T. Liu, Young‐Won Kim,

Nuclear Materials and Properties

Intermetallic TiAl-based alloys show a high susceptibility to the consistency of their surface region expressed by, e.g., a tendency to environmental embrittlement. In the present work, the prospects of near surface grain refinement of the β-stabilised TNM alloy and the first results of mechanical tests are presented and discussed. Grain refinement was done by remelting the surface region by a laser-based process. Adjusted parameters result in a refined surface area to a depth of approx. 225 μm and at the same time a smooth surface. Subsequent heat treatment at 900 °C for 6 h leads to a fine-grained duplex microstructure in the remelted area, with an average grain size of about 500 nm compared to 7.3 μm of the initial state. In the heat-affected zone below the remelted region, lamellar grains disappear by dissolving γ-lamellae during remelting. These lamellae are re-formed during heat treatment, but their spacing is significantly refined. Tensile tests reveal an increase of the tensile strength of remelted and heat-treated specimens by about 16% if compared to those with the initial microstructure. Failure in the remelted and heat-treated tensile specimens originates from the refined lamellar grains of the heat-affected zone.