Microstructure and mechanical properties of an extruded γ-TiAlMoSi alloy

Two samples of a two phase gamma/alpha (2)-Ti52A146.8Mo1Si0.2 alloy have been extruded with the reduction ratio in the cross section of 7:1 at 1250 degreesC and the ratio 12.5:1 at 1300 degreesC. Mechanical tests have been performed in the temperature regime from 20 to 1000 degreesC. The sample extruded at 1250 degreesC possesses a microstructure with gamma and alpha (2) grains with grain sizes of less than 3 mum and coarser single-phase gamma grains 10-40 mum in size. The alloy exhibits an excellent balance of ductility and strength. Al room temperature the yield strength is 720 MPa, the elongation to failure is is an element of (pl)=30% The ductility rapidly increases and the yield stress strongly decreases with temperature increases above 700 degreesC. The alloy extruded at 1300 degreesC has a similar microstructure as the alloy extruded at 1250 degreesC, but Lamellar grains exist near the rod axis. The yield strength of this alloy is higher within the considered temperature range, but its ductility is reduced (YS = 807 MPa, is an element of (pl) = 2.6% at room temperature). The loss in yield strength with increasing temperature of the 7:1 extruded TiAlMoSi alloy is much more pronounced than that of the 12.5:1 extruded TiAlMoSi alloy for temperatures higher than 600 degreesC. (C) 2001 Elsevier Science Ltd. All rights reserved.