Sothermal Solidification Of Sn Alloy Through Pressure

As a net-shape and near-net-shape forming method, pressure casting technology is widely used in the manufacturing sector because of its high efficiency and high precision casting size. We use pressure isothermal solidification based on pressure casting technology to obtain isometric crystal. Adding pressure when the alloy exhibits liquid to improve the melting point of the alloy and result in a degree of supercooling. Then the entire liquid metal is in a supercooled state and solidifies in a isothermal state. This molding method can provide a new theoretical practice for the pressure casting in the future.This paper mainly studies the influence of pressure isothermal solidification process on the microstructure of pure Sn, Sn-Bi alloy, Sn-Sb Alloy and the influence of alloying elements Cu,Zn on the microstructure of Sn-Bi alloy, Sn-Sb Alloy. Using optical microscopy, X-ray diffraction, sigma scanning electron microscope and other equipment to analyze the microstructure and phase composition of the alloy.The results show that: liquid pure Sn with the temperature of 240?solidified at the pressure of 312 Mpa, 499 MPa, 749 MPa can obtain isometric crystal.As the pressure increases,the equixed grain is refined and the refining effect is not obvious when continues to increase the pressure.liquid Sn-10%Bi with the temperature of 233?,liquid Sn-10%Bi-0.5%Cu with the temperature of 232?,liquid Sn-10%Bi-2%Zn with the temperature of 222? solidified at the pressure of 749 MPa can obtain isometric crystal.Cu-rich phase and Zn-rich phase separate out in the grain boundary when add a small amount of Cu and Zn in the Sn-10%Bi alloy. Then the Cu-rich phase and Zn-rich phase hinder the migration of grain boundaries and bring the pinning effect to refine the microstructure further.Liquid Sn-5%Sb with the temperature of 255.6 ?, Liquid Sn-5%Sb-Cu with the temperature of 254.9?,Liquid Sn-5%Sb-0.5%Zn with the temperature of 256.0? solidified at the pressure of 749 MPa can obtain isometric crystal.Cu-rich phase and Zn-rich phase separate out in the grain boundary when add a small amount of Cu and Zn in the Sn-5%Sb alloy. Then the Cu-rich phase and Zn-rich phase hinder the migration of grain boundaries and bring the pinning effect to refine the microstructure further.The pressure isothermal solidification method has changed the solidification mode of molten metal and improves the alloy's melting point; resulting in a degree of supercooling. Then making the molten metal to solidification in the entire volume; refining grains to obtain isometric crystal.