Microstructure, mechanical properties and corrosion resistance of A356 aluminum/AZ91D magnesium bimetal prepared by a compound casting combined with a novel Ni-Cu composite interlayer

• Published in: Journal of materials processing technology 2021-02, Vol.288, p.116874, Article 116874
• Main Authors: Li, Guangyu, Jiang, Wenming, Guan, Feng, Zhu, Junwen, Zhang, Zheng, Fan, Zitian
• Format: Article
• Language: English
• Subjects: A356/AZ91D bimetal; Aluminum base alloys; Bimetals; Compound casting; Copper; Corrosion resistance; Corrosion tests; Fractures; Interlayers; Intermetallic compounds; Magnesium base alloys; Magnesium compounds; Mechanical properties; Metal silicides; Microstructure; Nanohardness; Ni-Cu composite interlayer; Nickel; Phases; Rupture; Shear strength; Thickness
• ISSN: 0924-0136; 1873-4774
• DOI: 10.1016/j.jmatprotec.2020.116874

In the present work, a novel Ni-Cu composite interlayer was prepared on the surface of A356 aluminum alloy solid insert using the chemical nickel-plating and electro-coppering technology, in order to restrain the generation of brittle phases and enhance the shear strength of A356 aluminum/AZ91D magnesium bimetal manufactured using a compound casting. The effect of the Ni-Cu composite interlayer on the microstructure, mechanical properties and corrosion resistance of the bimetal was studied. The results show that the Ni-Cu composite interlayer effectively restrained the generation of the brittle and hard Al-Mg intermetallic compounds (IMCs). The interface layer of the A356/AZ91D bimetal without Ni-Cu composite interlayer was composed of Al3Mg2, Al12Mg17, δ-Mg and Mg2Si phases, while the interfacial reactants of the A356/AZ91D bimetal with Ni-Cu composite interlayer were mainly Al3Ni, Ni (Cu), Cu (Ni), Mg2Cu and Al7Cu3Mg6 phases. With the application of the Ni-Cu composite interlayer, the thickness of the interface of the A356/AZ91D bimetal remarkably decreased from 1400 μm of the sample without Ni-Cu composite interlayer to 40 μm. The shear strength of the A356/AZ91D bimetal using Ni-Cu composite interlayer increased by 20.3 % compared with that of the bimetal without Ni-Cu composite interlayer. The fractures of the A356/AZ91D bimetals with and without Ni-Cu composite interlayers belonged to a brittle rupture mode. The breakage of the bimetal with Ni-Cu composite interlayer mainly took place between the Ni-Cu layer and AZ91D matrix, while the rupture of the A356/AZ91D bimetal without Ni-Cu composite interlayer was located in the interface layer. The Cu(Ni) and Ni(Cu) layers had a lower nano-hardness than the Al-Mg IMCs, and the elasticity modulus for the Cu(Ni), Ni(Cu) and Al3Ni phases were higher compared to those of the Al-Mg IMCs. The results of corrosion test exhibited that the Ni-Cu composite interlayer had little influence on the corrosion resistance of the A356/AZ91D bimetal.