TWI

The influence of tool geometry and process conditions on the lap shear strength, weld integrity and efficiency during friction stir spot welding of magnesium alloys for automotive applications was investigated. The macro- and microstructures and weld failure modes were also examined. Welds were made in AZ31B-H24 sheet (2 mm thickness), AM30 extrusion (2.5 mm thickness) and AM60 casting (2 mm thickness) using a cylindrical threaded pin tool and a triangular shaped pin tool, made of H13 tool steel, with concave shoulders but different pin geometries. The superior strength of the welds obtained using the triangular shaped pin is discussed. The key role of the placement of the workpiece and the overlapped dissimilar materials in determining the spot strength is discussed, particularly in terms of formability and hook height. An approach is also proposed for evaluating weld efficiency.

8th International Symposium, 18-20 May 2010, Session 8A: Non Ferrous, Paper 01