Abstract: The Cu₆₀Ni₂₀Cr₂₀ bulk alloys have been prepared respectively by arc-melting and hot pressing the mechanically alloyed powders at 750℃ under a normal pressure 58MPa with much different grain sizes. Their micro-structural characteristics were investigated by X-ray diffraction(XRD), scanning electron microscopy(SEM) and energy-dispersive X-ray microanalysis(EDX). The results show that with the increase of ball milling time, the X-ray diffraction peaks have a deviation and broadening because of fine grain size and internal stress and the solid solubility of Cr in Cu increases evidently. When the powders were milled for 40h, the alloyed powders have become single solid solution. Because mechanically alloyed powders are in non-equilibrium state, the solvent in a state with certain degree of super-saturation can decompose slowly, finally the alloys have become double-phase from single phase solid solution. The sizes of α-Cu and γ-Cr phase particles increased but still remained nano-size after hot pressing and annealing in vacuum. The alloy possessed excellent density and showed little oxidation by SEM/EDX analysis. The effect of grain size on alloys microstructue was discussed in detail. 

Key words: Cu₆₀Ni₂₀Cr₂₀ alloy; mechanical alloying; grain size; microstructure