Microstructure and Corrosion Behaviors of High-Strength and High-Elasticity Cu-20Ni-20Mn-xGa Alloys

Cu-20Ni-20Mn-xGa (x = 1, 5 wt.%) alloys with high strength and elasticity were prepared and tested for corrosion properties in 3.5 wt.% NaCl solution. The hardness, tensile strength, elongation, and annual corrosion rate of the Cu-20Ni-20Mn-1 Ga alloy reached 1368 MPa, 442 HV, 8.63%, and 0.0262 mm/year, respectively, while those of Cu-20Ni-20Mn-5 Ga alloy were 1278 MPa, 428 HV, 2.5%, and 0.0119 mm/year, respectively. The excellent mechanical properties were attributed to the nanoscale NiMn phase which can strengthen the copper matrix. In addition to grain refinement, the addition of Ga also reduced the cathodic current. Also, the corrosion products of the two alloys in 3.5 wt.% NaCl solution were mainly oxides and chlorides. The Cu-20Ni-20Mn-5 Ga showed better corrosion resistance with more gallium-rich oxides in the corrosion product film to resist corrosion.