Structure and properties of a near-α titanium alloy after β solution treatment and aging at 625 °

The microstructure, tensile properties, and fractographic features of a near alpha titanium alloy, IMI 829 (Ti-6.lAl-3.2Zr-3.3Sn-lNb-0.5Mo-0.32Si) have been studied after aging at 625 ° for 24 hours following solution treatment in the beta phase field at 1050 ° and cooling at various rates (furnace, air, oil, or water). Transmission electron microscopy studies revealed that aging at 625 ° for 24 hours of this alloy had led to the precipitation of only one kind of silcide with a hexagonal structure (c = 0.36 nm andα = 0.70 nm). The precipitates are ellipsoidal in shape and their size depends on the cooling rate given to the alloy after beta solution treatment. Extremely fine precipitation of Ti₃Al phase has also been observed in the furnace cooled and aged condition. There is a significant improvement in both yield and ultimate tensile strengths after aging of both the oilquenched and water-quenched specimens whereas it is minimal in the case of furnace-cooled and air-cooled specimens. Aging the alloy has also resulted in a drastic reduction in both percentage elongation and percentage reduction in area for all the conditions investigated. While the fracture surfaces of the unaged specimens showed characteristic dimples, a large number of facets appeared in the fractographs of the aged specimens. formerly with Banaras Hindu University, is with the National Metallurgical Laboratory, Jamshedpur, India.