Microstructures and Mechanical Properties of Al-7Sn-1.1Ni-Cu-0.2Ti Bearing Alloy

Abstract

The microstructures and mechanical properties of Al-7Sn-1.1Ni-Cu-0.2Ti alloy were studied by using SEM, EDS, OM and WDW-100KN universal tensile testing machine, the lubricating properties were completed by the disk-pin testing machine. The results show that the solidification shrinkage of alloy is 1.13%; the tensile strength, yield strength, elongation and Brinell hardness in the as-cast state are 191, 147MPa, 15.6% and 34.6HBS, with the executing of low temperature aging and annealing process, the tensile strength increases slightly and the yield strength has no significant changes; the elongation and Brinell hardness exhibit the tendency of increasing firstly and then decreasing. Morphology of eutectic Sn phase that distributes nearby the grain boundary transforms from plate-like shape and bone-shape to lamellar and short rod gradually under the function of the interfacial tension. Due to some eutectic phase melts by absorbing energy from heat treatment process, cavity structure forms around grain boundaries, the average grain size of primary α-Al substrate is 182μm. Comparing with the as-cast and annealing at 340℃ for 6h states, the friction coefficient decreases by 28.6% and 78.6%, together with the wear volume reduces by 157.1% and 471.4% after aging at 175℃ for 10h, the fracture morphology shows mainly intergranular fracture and dimple fracture.

Keywords

• bearing alloy
• microstructure
• mechanical property
• friction and wear