Effect of solution-aging treatment on microstructure and high temperature fracture toughness of Ti60 alloy rolled sheet

In this study, the Ti60 alloy rolled sheet was solution-aging treatment at different temperatures, and then the high temperature fracture toughness test was carried out on the samples after solution-aging treatment. The microstructure morphology and crack propagation behavior were studied. The original microstructure of the Ti60 alloy rolled sheet is composed of primary alpha phase and flocculated alpha phase. The microstructure of Ti60 alloy rolled sheet after solution-aging treatment is a typical bimodal structure. It is mainly composed of acicular alpha s phase, equiaxed alpha phase and lamellar alpha phase. The proportion of equiaxed alpha phase gradually increases from 46 % to 82 % with the increase of solution treatment temperature. After 1080 degrees C/2 h/AC + 700 degrees C/2 h/AC solutionaging treatment and 1090 degrees C/2 h/AC + 700 degrees C/2 h/AC solution-aging treatment, lamellar alpha appears inside the equiaxed alpha grains. After 1100 degrees C/2 h/AC + 700 degrees C/2 h/AC solution-aging treatment, the lamellar alpha will be transformed into acicular alpha s. The average KIC value of the original Ti60 alloy rolled sheet is 46.35 MPa center dot m1/2. The KIC values of the samples after 1070 degrees C/2 h/AC + 700 degrees C/2 h/AC solution-aging treatment, 1080 degrees C/2 h/AC + 700 degrees C/2 h/AC solution-aging treatment and 1100 degrees C/2 h/AC + 700 degrees C/2 h/AC solution-aging treatment is approximately in the range of 44.15 MPa center dot m1/2-51.33 MPa center dot m1/2. But the average KIC value after 1090 degrees C/2 h/AC + 700 degrees C/2 h/AC solution-aging treatment is increased to 74.56 MPa center dot m1/2. This may be due to the appearance of lamellar alpha, which makes the fracture toughness of Ti60 alloy rolled sheet increase significantly.