Influence of Ni‐Coating Thickness on Interface Microstructure and Mechanical Properties of Mg/Ti Bimetal via Compound Casting

Abstract

In this article, the influence of Nickel (Ni)coating thickness on the interfacial microstructure and mechanical properties of AZ91D/Ti–6Al–4 V bimetal fabricated by compound casting is investigated. In the results, it is shown that the Ni coating and its thickness have a significant effect on the interfacial phase compositions and mechanical properties of AZ91D/Ti–6Al–4 V bimetal. At a Ni‐coating thickness of 6.5–27.3 μm, it transforms into α‐Mg + Mg2Ni eutectic structures + blocky τ‐Ni2Mg3Al ternary compounds at the interface zone. When the Ni‐coating thickness increases to 36.1 μm, part of the Ni coating remains, and the interface layer forms, comprising the Ni solid solution layer, Mg2Ni layer, τ‐Ni2Mg3Al ternary compounds, and α‐Mg + τ‐Ni2Mg3Al particles from Ti–6Al–4 V to AZ91D side in sequence. The microhardness of the interface zone is lower than that of the Ti–6Al–4 V but higher than AZ91D. The bimetal shear strength reaches a maximum value of 87.6 MPa at a Ni‐coating thickness of 19.7 μm enhanced by 78.5% in comparison with that of the bimetal without Ni coating. The results are helpful to further enrich the interface control method of compound casting of Ti/Mg bimetal and determine the ideal interlayer thickness for maximizing interface strength.