Effect Of Warm Rolling And Annealing On Microstructure And Properties Of Semi-Solid CuSn10 Alloy

Copper-tin alloy has many advantages such as high strength,low coefficient of friction,corrosion resistance,etc.It is widely used in high speed rail,ship,aviation and other industries.The copper-tin alloy castings obtained by conventional casting will have a coarse dendritic morphology and high intergranular brittleness caused by the enrichment of tin elements,resulting in a poor plastic deformation capacity of the alloy,which is not easy to obtain strong plasticity coordinated products.The coppertin alloys obtained by the semi-solid state technology have better plasticity and better deformability than conventional processes due to their equiaxed morphology and improved elemental segregation,and have good plastic processing properties.In this Thesis,the semi-solid Cu Sn10 alloy was isothermally rolled and deformed with deformations of ε=0,0.1,0.2,0.4 and 0.6 at a temperature of 350 °C using a two-roll synchronous rolling mill.The rolled deformed Cu Sn10 alloy with a deformation of ε=0.6 at 350 °C was selected and subjected to stress relief annealing heat treatment at 250～450 °C.The evolution of the organization and properties of the semi-solid Cu Sn10 alloy during rolling deformation and annealing treatment was studied.The study showed that the increase in rolling deformation caused a significant reduction of casting defects such as shrinkage and shrinkage holes in the organization of semi-solid Cu Sn10 alloy,the grains were continuously elongated and refined along the rolling direction,the average grain thickness decreased from 30.58 μm at ε=0 to15.69 μm at ε=0.6,and the number of deformation twins in α-Cu grains increased with the increase in deformation.No significant diffusion of elements during rolling deformation was observed.The EBSD inspection found that the increase in deformation caused the grains to deflect,and the grain orientation was mainly <101>and <111> orientations at ε=0.6,with strong [101],[111] and [001] weaving in the polar diagrams {110} and {111},and the increase in deformation caused a large number of dislocations to be introduced in the Cu Sn10 alloy,producing an obvious work-hardening effect.The yield and tensile strengths of the Cu Sn10 alloy were enhanced by grain refinement and work hardening,increasing from 215 MPa and 330 MPa at undeformation to 541 MPa and 647 MPa at ε = 0.6.After rolling deformation of Cu Sn10 alloy in the 250 ～ 450 ℃ annealing process,the higher the annealing temperature,the longer the annealing time is conducive to the generation and growth of recrystallized grains,recrystallized grains often appear in the emergence of high distortion at the grain boundaries and gradually consume the deformed matrix.Cu Sn10 alloy at 250 ～ 350 ℃ short annealing without obvious crystallization,with the annealing time up to 60 minutes before the more obvious recrystallization grains,and in 450 ℃ short annealing at the obvious recrystallization grains and with the extension of the annealing time recrystallization grains gradually grow so that the deformation grain profile gradually tends to disappear.Cu Sn10 alloy did not show elemental diffusion during annealing at different times from 250 to450 °C.Cu Sn10 alloy in the annealing process with the annealing temperature increases and annealing time in the extension of its strength and hardness gradually decreases,the elongation continues to increase.After annealing at 250 °C due to Unfavorable dislocation cancellation and annihilation and recrystallization of nucleation,although the alloy with high strength and hardness,the lower in elongation.After annealing at 450 ℃ because of the increase in the number of recrystallization and recrystallized grains continue to grow consuming the work hardening,although the alloy elongation is high but the strong hardness decreases sharply.After annealing at 350 °C,thanks to the stress relief and partial recrystallization in the organization of the alloy,the alloy’s organization is regulated so that the coordination of hardness and plasticity is higher,and the Cu Sn10 alloy with excellent overall performance can be obtained.In this Thesis,we study the evolution of the organization and mechanical properties of the semi-solid Cu Sn10 alloy during the rolling deformation process and annealing process,which improves the mechanical properties of Cu Sn10 alloy to a certain extent and has some reference value for the practical industrial application of Cu Sn10 alloy.