Evolution of grain characteristics and dynamic recrystallization behavior of Cu-15Ni-8Sn alloy under different extrusion ratios

For atmospheric melting cast Cu-15Ni-8Sn alloy, hot extrusion tests were conducted on ingots of Cu-15Ni-8Sn alloy with varying extrusion ratios (5, 12 and 16) following homogenization and annealing. The investigation employed mechanical property tests, scanning electron microscopy and transmission electron microscopy to analyze the mechanical characteristics, dynamic recrystallization and twinning behaviors of the alloys subjected to different extrusion ratios. The findings revealed a reduction in the average grain size of the alloy as the extrusion ratio increased. The alloy undergoes dynamic recrystallization during hot extrusion, and the degree of recrystallization of the alloy escalated with higher extrusion ratios. The alloy underwent completely recrystallized at an extrusion ratio of 16, primarily driven by discontinuous dynamic recrystallization (DDRX). In addition, the alloy generated twins during the DRX process, and the twin boundaries provided favorable sites for the nucleation of DRX grains, which promoted the DRX of the alloy. Notably, at an extrusion ratio of 16, the alloy demonstrated impressive mechanical properties, with an ultimate tensile strength of 836 MPa and an elongation of 13.5 %. These results presented a substantial enhancement, showcasing a 54 % increase in the extruded ultimate tensile strength and a 350 % increase in the elongation compared to that of the alloy in the homogenized annealed state.