The effects of heat treatment on microstructure

electric conductivity and hardness of Cu-0.8Cr-0.15Zr-2.8Co-0.7Si-0.1RE alloy were investigated by optical microscopy

scanning electron microscopy

energy dispersive spectroscopy and X-ray diffraction.The results show that the as-cast microstructure of the alloy exhibits equiaxed grains

and a large number of Co

5

Cr

3

Si

2

phase and gray precipitates containing Co

Si are distributed in the matrix.After solid solution treatment

the grain size is obviously increased

and the grey precipitated phase is fully dissolved

however

the Co

5

Cr

3

Si

2

phase is not dissolved.After aging treatment

the precipitation particles are mainly Co

5

Cr

3

Si

2

Co

2

Si phase.With the increase of solid solution temperature

electric conductivity of the alloy is decreased rapidly

while the hardness is increased rapidly.After aging treatment

the electric conductivity and hardness of the alloy are improved greatly.After 980 ℃×2h solution treatment+450 ℃×10h aging treatment

the hardness

electric conductivity and softening temperature of the alloy reach 218.9HV

28.54MS/m and 686℃

respectively.