Formation of zinc interlayer texture during dissimilar ultrasonic spot welding of magnesium and high strength low alloy steel

Ultrasonic spot welding (USW) of AZ31B-H24 magnesium alloy sheet to high strength low alloy (HSLA) steel sheet with a zinc interlayer was successfully achieved. Thin layer of intermetallic compounds (IMCs) of Mg7Zn3, Mg2Zn11 and MgZn2 were present at the interface between magnesium and zinc substrate, while at the other interface (iron and zinc), no IMCs were found. A single crystal-like strong basal crystallographic texture in a zinc interlayer was identified. The (0 0 0 2) peak intensity of zinc interlayer after ultrasonic spot welding became ∼30 times higher than that of cold-rolled pure zinc sheet, with basal plane predominantly parallel to the interlayer surface. This was due to the plastic deformation arising from the ultrasonic vibrations, which serve to strengthen the basal texture. The basal plane peak intensity in zinc interlayer was higher when rolling direction (RD) of zinc sheet was aligned perpendicular to the vibration direction than when it was aligned in parallel.

► USW of Mg alloy to HSLA steel sheet with Zn interlayer was successfully achieved.
► USW creates strong single crystal-like basal plane texture in Zn interlayer.
► (0 0 0 2) peak intensity of Zn interlayer after USW becomes 30 times higher compared to cold rolled Zn sheet.
► Once strong basal plane texture is formed there is no further effect of strain through increased energy input.