Intermetallics formed at interface of ultrafine grained Al/Mg bi-layered disks processed by high pressure torsion at room temperature

•A Mg/Al bilayered disk is bonded by high pressure torsion at room temperature.•A very thin layer of γ-Mg17Al12 of 260 nm in thickness is formed at the interface.•Forming γ phase at low temperature is due to high pressure and large strain, etc.•No other phases were detected, which is attributed to high interfacial energies

In this work, Mg/Al bi-layered disks were fabricated by high pressure torsion (HPT) at room temperature. A 0.26 µm layer of γ-Mg17Al12 intermetallic formed at the interface of Mg/Al disks. This is very different to the interface of Mg/Al produced by other techniques such as diffusion bonding and friction stir welding where both γ-Mg17Al12 and β-Al3Mg2 form and the β-Al3Mg2 layer is much thicker than the γ-Mg17Al12 layer. This unusual phenomenon is attributed to the interfacial energies of intermetallics and the effect of room temperature HPT on diffusion of Al in Mg and the γ-Mg17Al12 layer.

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