# Study on the Influence of Nickel Plating on the Structure and Properties of Aluminum/Steel Bimetallic Bonding

## TL;DR

This study explores how nickel plating improves the bonding strength between aluminum and steel in bimetallic materials.

## Contribution

The novel use of a 50 μm Ni interlayer effectively controls interface layer thickness and enhances bonding strength.

## Key findings

- A 50 μm Ni interlayer effectively controls the transition layer thickness and improves interfacial bonding strength.
- The interface layer thickness increases with hot-dip duration but reaches optimal bonding strength at 240 seconds.
- Shear strength of Al/steel bimetal with Ni interlayer is 75% higher than Ni-free counterparts at 240 seconds.

## Abstract

Aluminum/steel bimetal combines the advantages of aluminum alloy and steel, greatly leveraging the value of various industrial fields, especially in improving engine performance and fuel economy. However, it is very difficult to prepare products with good interface bonding strength. The fundamental issue stems from the presence of an excessively thick interface layer and brittle intermetallic compounds. Therefore, this study employed a 50 μm-thick Ni interlayer to control the interface layer thickness, thereby enhancing the Al/steel interfacial bonding strength. A systematic investigation was conducted on the effects of hot dip duration on the interfacial microstructure and mechanical properties of Al/steel bimetal. The influence of hot dip duration on the microstructure and mechanical properties of aluminum/steel bimetal interface was systematically studied. The results show that the 50 μm Ni intermediate layer was used to effectively control the transition layer thickness and improve the interfacial bonding strength of aluminum steel. The thickness of the interface layer gradually increases with the increase in the hot-immersion time. The thickness of the interface layer composed of the two phases of τ1-Al2Fe3Si3 and FeAl3 on the steel side increases first and then decreases, while the interface layer composed of the two phases of τ5-Al8Fe2Si and Fe2Al5 on the aluminum side decreases first and then increases. When the hot dip time is 240 s, the shear strength of Al/steel bimetal with 50 μm Ni interlayer showed 75% enhancement compared to Ni-free counterparts.