Effect of Ga on the microstructure and properties of NiCoV alloy at different annealing temperatures

Abstract

To obtain a high-entropy alloy characterized by high strength and plasticity, (NiCoV)_100-xGa_x (x ​= ​0, 5, 7) was successfully prepared, cold-rolled, and heat-treated. The microstructure was analyzed to correlate Ga content with the performance of the system. The addition of Ga can produce alloying effects, including solid solution strengthening effect, second phase precipitation strengthening effect, and layer misalignment energy reduction effect. The experimental results show adding Ga elements can enrich Ni, Co, V, and Ga above the grain boundaries, causing the alloy to produce annealed twins inside. The alloy is strengthened mainly by precipitation, and the formation of the precipitation phase effectively enhances the strength of the alloy. The low stacking fault energy promotes the toughening of NiCoV but makes the plasticity of the alloy decrease. Still, the formation of annealed twins effectively increases the plasticity, which makes the alloy harder but does not reduce the plasticity too much. By comparing the experimental properties, (NiCoV)₉₃Ga₇ showed the best mechanical properties at the annealing temperature of 900 ​°C, yield strength, tensile strength and elongation of 906 ​MPa, 1321 ​MPa and 21.36 ​%, respectively.