Investigation On The Thermomechanical Processing Of Cu-3Ti-2Mg Alloy

The microstructures and properties of Cu-3Ti-2Mg alloy at as-cast state,solid solution and aging state were investigated,and the effect of prior cold rolling on the microstructure and properties of Cu-3Ti-2Mg alloy was studied as well.The microstructures and phase constituents were characterized by optical microscope(OM),scanning electron microscope(SEM),X-ray diffractometer(XRD)transmission electron microscope(TEM)and electron backscattering diffraction(EBSD),and the hardness,electrical conductivity,elastic modulus,yield strength and friction coefficient were measured.The following conclusions can be obtained from above investigations.(1)The as-cast Cu-3Ti-2Mg alloy presents typical dendrite microstructure and mainly consists of a-Cu(Ti,Mg)and Cu2Mg phase.The electrical conductivity and hardness of Cu-3Ti-2Mg alloy are 11.5%IACS and 259HV,respectively.(2)After homogenization at 800? for 10h and solution treatment at 700? for 4h,the Cu-3Ti-2Mg alloy has the minimum electrical conductivity and hardness.(3)The strengthening effect of the Cu-3Ti-2Mg alloy can be attributed to the formation of precipitated Cu2Mg phase and continuous ?'-Cu4Ti.With the increase of the aging time and the temperature,?' phase transforms into the ?-Cu3Ti phase which is incoherent,with the Cu matrix,the Cu2Mg phase becomes coarsening,thereby decreasing the hardness.Due to the formation of Cu2Mg,?'-Cu4Ti,?-Cu3Ti and ?-Cu4Ti5 Ti concentrations are reduced efficiently in the Cu matrix,and thus,increasing the electrical conductivity of Cu-3Ti-2Mg alloy.(4)The cold rolling before aging enhances the distortion energy of Cu-3Ti-2Mg alloy and promotes the precipitation of secondary phases.Consequently,the electrical conductivity and hardness of Cu-3Ti-2Mg alloy increase remarkedly and the aging time to reach the peak hardness is shortened.After 70%cold rolling and aging at 450? for 3h,the hardness,electrical conductivity,elastic modulus,yield strength and friction coefficient of Cu-3Ti-2Mg alloy are 18.1%IACS,362HV,141.12GPa,1.004GPa and 0.66,respectively.