Study of Microstructure and Mechanical Properties of Similar and Dissimilar FSW of Al 7075 and Mg AZ31 Alloys Without and With Zn Interlayer

The similar and dissimilar joining of Al and Mg alloys are important in aerospace and automobile industries. The Al 7075 and Mg AZ31 alloys are mostly used in the industries due to their light weight and high strength properties. In present work four FSW of similar Al 7075, similar Mg AZ31, dissimilar Al 7075 and AZ31 without interlayer and dissimilar Al 7075 and AZ31 with Zn interlayer has been studied at 1300 rpm rotational speed and 20 mm/min traverse speed, corresponding stir zones (SZ) have also been investigated. It was found that, the dissimilar FSW of Al 7075 and Mg AZ31 alloys without interlayer has formed defects (such as cracks, void, tunneling and kissing bonds) due to the formation of brittle phases viz. Al3Mg2 and Al12Mg17. Therefore, the Zn interlayer was induced in between the faying surface of Al and Mg alloys FSW which led to defect free joint. During stirring the Zn has reacted with Mg and Al, and formed different phases such as Al-Mg-Zn and Mg-Zn, which inhibited the formation of Al3Mg2 and Al12Mg17 IMCs layers. The joint efficiency of similar FSW of Al 7075 attained 55% (285 MPa) and Mg AZ31 attained 91% (225 MPa). The dissimilar FSW without interlayer has formed immediate cracking and no strength has been achieved. Whereas, the dissimilar FSW with Zn interlayer attained 34% joint efficiency of AZ31 (85 MPa).