Effect Of Heat Treatment And Rolling On Microstructure And Properties Of Cu-0.5Y-xZr(Wt.%)Alloys

Cu-Zr alloy is a typical kind of aging strengthened alloy.It has excellent mechanical performance as well as extremely high thermal and electrical conductivity.It has already been widely used in the integrated circuit,contact wires of high speed rail,electromotor and other fileds.Its excellent performance and bright prospect have attracted more and more researchers’ attention,and it has gradually become one of the important research contents of copper alloys in recent years.The addition of a proper amount of rare earth elements in Cu-Zr alloy can purify the melt and improve the mechanical properties of Cu-Zr alloy effectively.Therefore,the study of Cu-Zr-RE alloy is pretty necessary.At present,the domestic researches on Cu-Zr-RE alloy mainly focus on the influence of mixed rare earth elements on the micro structure and properties of Cu-Zr alloy.The analysis of the influence of RE elements on the microstructure and properties of Cu-Zr alloy during deformation and heat treatment has not been deeply conducted yet.The researches on the influence of single rare earth element Y on the microstructure and properties of Cu-Zr alloy are limited.The evolution regulations of microstructure and properties of Cu-Zr-Y alloy during heat treatment and deformation are rarely studied.In this paper,Cu-0.5Y-xZr(wt.%,x=0.05/0.1/0.15/0.2)alloys were designed and vacuum-melted.The heat treatment and rolling deformation were then carried on the as-cast alloys.The research aims were to prepare excellent performance Cu-0.5Y-xZr alloys by studying the existence forms of Y and Zr elements in copper alloy and the rules of interaction between the matrix and second phases during heat treatment and rolling deformation as well as the influence of heat treatment parameters and rolling deformation parameters on the microstructure and properties of the alloys.The microstructures of the as-cast,heat-treated and rolled Cu-0.5Y-xZr(wt.%,x=0.05/0.1/0.15/0.2)alloys were observed by scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),X-ray diffraction(XRD)and transmission electron microscopy(TEM).The mechanical properties of the alloys were tested using a microhardness tester and a universal testing machine.The main findings are as follows:(1)Precipitated phases with three different morphologies were found by observing the SEM images of aged Cu-0.5Y-xZr(wt.%,x=0.05/0.1/0,15/0.2)alloys.They are large-sized elongated precipitate phase precipitated along the grain boundary,rod-shaped and block-like precipitate phases with the sizes bellow 30μm in the grain.In addition,with the increase of Zr contents,the quantities of rod-shaped and block-like precipitate phases increase,while that of the elongated precipitate phases decrease.(2)Cu-0.5Y-0.05Zr(wt.%)alloy obtained the maximum hardness after aging at 460℃ for 3 h with the value of 84.89 HV.Cu-0.5Y-xZr(wt.%,x=0.05/0.1/0.15/0.2)alloys gained the maximum hardness after aging at 460℃ for 2 h,and the maximum hardness were 87.35 HV,92.24 HV and 95.16 HV,respectively.The electrical conductivities of Cu-0.5Y-xZr(wt.%,x=0.05/0.1/0.15/0.2)alloys could be greatly improved after aging at 460℃ for 3 h.And then the electrical conductivities tended to be stable with the prolongation of aging time.(3)As the rolling reduction increased,the strength and hardness of the Cu-0.5Y-xZr(wt.%,x=0.05/0.1/0.15/0.2)alloys were gradually improved.The elongations of the Cu-0.5Y-xZr(wt.%,x=0.05/0.1/0.15/0.2)alloys decreased significantly compared to as-cast alloys.However,the elongations were slowly increased with the increasing of the reduction.In addition,the conductivities of Cu-0.5Y-xZr(wt.%,x=0.05/0.1/0.15/0.2)alloys decreased with increasing of reduction.