High entropy mechanism of nugget in Ta1/0Cr18Ni9 sheet energy storage welding

In this paper, in view of the difference of physical and chemical properties between tantalum and steel,which is easy to produce brittle intermetallic compounds during welding, resulting in poor performance and cracks of fusion welded joints. According to the idea of high entropy technology of nugget metal, a new type of interlayer alloy Ta₂₀Fe₂₀Ni₂₀Cr₂₀Co₂₀ was designed based on the first principles of thermodynamics based on density functional theory. Combined with fusion ratio, the composition of intermediate layer alloy suitable for tantalum/steel energy storage welding is Ta₇Ni₃₂Cr₁₉Co₄₂. The button alloy ingot was melted by vacuum arc furnace, and then the middle alloy foil was prepared by single roll quenching method, which was used for energy storage welding connection of Ta1/0Cr18Ni9 sheet. The results show that under the condition of energy storage welding, Ta1/Ta₇Ni₃₂Cr₁₉Co₄₂/0Cr18Ni9 lap joint has formed a flat spherical nugget with regular and complete morphology and about 0.8 mm long diameter, and the nugget has shifted to the steel side as a whole.The nugget structure consists of simple FCC solid solution and no intermetallic compound precipitation. It has typical characteristics of high entropy alloy and realizes high entropy of nugget metal. The average strength of Ta/Ta₇Ni₃₂Cr₁₉Co₄₂/0Cr18Ni9 energy storage welding joint can reach 395 MPa under the welding voltage of 1 000 V, capacitance of 500 μF and electrode pressure of 30 N.