Effects of graphene nanosheets addition on microstructure and mechanical properties of SnBi solder alloys during solid-state aging

In this work, graphene nanosheets (GNSs) functionalized SnBi solder alloys were synthesized and the effects of GNSs addition on the microstructure evolution and mechanical properties of SnBi alloys during solid-state aging were investigated. The results show that the microstructure and mechanical properties of solders enhanced by 0.03 wt% GNSs addition possess the best performance during solid-state aging. After 360 h aging at 100 °C, the coarse microstructure and growing grains in pure SnBi are effectively inhibited in the GNSs reinforced solders, meanwhile the ultimate tensile strength and elastic modulus of pure samples are improved by 15% and 24% in SnBi-0.03GNSs samples. The failure features after aging show that GNSs can restrain the formation and propagation of micro-cracks at the fracture surface of SnBi alloys. The hardness of solders is also enhanced by GNSs and varies with tensile strength following a linear relationship. Moreover, the strengthening mechanism of GNSs in the composite solders during aging treatment is also analyzed.