1992 Volume 78 Issue 6 Pages 941-946
High-low two-step aging treatment was applied to a Ti-15V-3Cr-3Sn-3Al alloy TIG weldment in order to improve the mechanical properties of it. Strength of a fusion zone and base metal is rather different after aging at a single temperature because of aging enhancement in the fusion zone. In the first high temperature aging of the two-step aging, coarse alpha particles which strengthen little and suppress streng-thening by fine alpha precipitation in following low temperature re-aging, precipitate in the fusion zone more than in base metal because of the enhancement of aging in the fusion zone. Hence, strengthening of the fusion zone in re-aging is less than in the base metal and comparable strength between the fusion zone and the base metal is obtained through the two-step aging. Bi-modal microstructure of coarse and fine alpha precipitates in beta matrix produced by this aging treatment improves the fracture toughness of the fusion zone of the weldment.