Hot Compression Deformation Behavior And Microstructure Evolution Of Semi-solid CuSn10P1 Alloy

High tin content cast copper-tin alloy has the advantages of high strength,large modulus of elasticity,low friction coefficient,good wear resistance and corrosion resistance,etc.It has become the first choice for high-iron contact wires instead of copper-silver alloy,and is widely used to manufacture bushings,housings,gears and worm gears which is applied to high-speed rail,ships and aviation industry.However,in the metal casting with faster cooling rate,the copper-tin alloy is prone to segregation and reverse segregation,and its intergranular brittleness is large and cracking is easy to occur during the deformation process,which greatly limits the development of high-performance pin sleeve parts for applications such as connecting rods.In this paper,the Gleeble-3500 thermomechanical simulation test machine was used to perform unidirectional isothermal compression deformation of conventional as-cast and semi-solid CuSn10P1 alloy cylindrical specimens.The deformation behavior and microstructure evolution of the alloy during plastic deformation are studied.It is found that for conventional as-cast samples,compared with semi-solid samples,under the same deformation conditions,the peak stress reached during compression deformation is small,and the corresponding true strain is greater when the peak stress is reached.The process is longer,the dynamic recrystallization is produced later,and the dynamic recrystallized grain distribution is not uniform.For semi-solid samples,when the other deformation parameters are the same,the strain rate increases,the dynamic recovery process is prolonged,the degree of dynamic recrystallization is reduced,and the strain rateεis obtained at 450℃、500℃and 550℃compression deformation.The semi-solid samples with?ε?=1s^-1 have the highest peak stresses of 273MPa,178MPa and 124MPa,respectively,and the corresponding true strainsεare0.36,0.28 and 0.21,respectively.With the deformation temperature from 550℃ to 500℃and then to 450℃,the maximum stress reached by the semi-solid sample gradually increases.Before the occurrence of the maximum stress,the change of alloy structure is mainly dynamic recovery.The higher the temperature,the easier the dynamic recovery is.The maximum stress decreases with increasing temperature.The larger the strain rate,the more serious the dislocation accumulation phenomenon and the dislocation density.The larger the greater the maximum stress.During the stress drop after the maximum stress,the alloy microstructure changes mainly by dynamic recrystallization,and the strain corresponding to dynamic recrystallization decreases with increasing temperature.The microstructure of CuSn10P1 alloy at room temperature includes primaryαphase and（α+δ+Cu₃P）eutectic structure.It is found in the deformed structure of semi-solid CuSn10P1alloy that the distribution of Sn element is from grain boundary to primaryαphase grain core.The content of P is decreasing,while the P element is mainly distributed in the intergranular structure in the form of Cu₃P.The content of P in the primaryαphase and recrystallized grains is extremely low.The dynamic recrystallization is preferentially generated in the region with high Sn element content at the edge of the primaryαphase.As the deformation increases,the distribution of Sn element in the tissue becomes more and more uniform,and the recrystallized region gradually advances toward the center of the primary phase.It is found by EBSD that as the deformation increases,the average grain size of the sample decreases,and the number of small-angle grain boundaries decreases accordingly.The large-angle grain boundaries,especially the grain boundary ratio of>60°,increase in the deformed structure.Most of the grain orientation is in the typical face-centered cubic[101]direction.Through TEM analysis of the sample,it was found that there were a large number of slip bands in the deformed sample at 450°C and 1 s^-1,and there was a clear boundary between the slip zone and the recrystallized grains.