Effect of Solution Temperature on Microstructure and Properties of Thixotropic Back-Extruded Tin Bronze Shaft Sleeve

The thixotropic back-extruded tin bronze shaft sleeves were heat-treated at 630 °C, 660 °C, 690 °C and 720 °C for 1 h, respectively. The effect of solution temperature on the microstructure and mechanical properties of thixotropic back-extruded tin bronze shaft sleeve was studied by means of a metallographic microscope, scanning electron microscope, transmission electron microscope, hardness tester and tensile tester. The results show that the solid solution treatment can improve the semi-solid microstructure morphology and intergranular microstructure distribution uniformity, and improve the comprehensive mechanical properties of the tin bronze shaft sleeves. With the increase of solution temperature, the Brinell hardness increases, the tensile strength increases firstly and then decreases, and the elongation decreases gradually. After solution treatment at 690 °C for 1 h, the tin bronze shaft sleeve's microstructure and comprehensive mechanical properties are the best. The shape factor is 0.75, the average grain size is 82.52 μm, Brinell hardness is 122 HBW, tensile strength is 437 MPa, elongation is 17.4%, which is 3.4 times higher than that before solution treatment