Effect of Heat Treatment Temperature on the Spinning Structure and Properties of a Cu-Sn Alloy.

A thin-walled copper (Cu)-tin (Sn) alloy cylinder was treated after spinning at 200-400°C for 0.5 h. The characteristics of the alloy microstructure under different temperatures were analyzed through electron back-scattered diffraction. The results were as follows. The grain size at 200-300°C decreases as the heat treatment temperature rises, but the grain size at 400°C increases. At 200-300°C, the microstructure primarily consists of deformed grains. It is found that the main reason for the formation of high-angle grain boundaries (HAGBs) is static recrystallization. For the grain boundary orientation differential, the low-angle sub-grain boundary gradually grows into the HAGB, and multiple annealing twin Σ9 boundaries appear. Grain orientation is generally random at any temperature range. The mechanical property test indicated that, at the upper critical recrystallization temperature of 300°C, the elongation of the Cu-Sn alloy gradually increases, and its yield strength and ultimate tensile strength rapidly decrease.