Appropriate amount of TiB2 particles causes the ductile fracture of the un-weldable spray-formed 7055 aluminium alloy TIG-welded joint

Abstract

Spray-formed 7055 aluminium alloy is often referred to as an un-weldable aluminium alloy because of the low strength and high brittleness of the fusion welding joints prepared using the traditional welding wires. In this study, new welding wires with different content of TiB2 particles were developed, and the spray-formed 7055 aluminium alloy was welded using these wires in conjunction with the use of the TIG welding method. The microstructure and tensile properties of the TIG-welded joints were investigated. The results show that TiB2-7055 welded joints gradually change from coarse grain to fine equiaxial grain as a function of the content of TiB2 particles, and their tensile strengths and elongations first increase and then decrease. The tensile strength and elongation of 0 wt.% TiB2-7055, 0.5 wt.% TiB2-7055, 1.5 wt.% TiB2-7055 and 3.0 wt.% TiB2-7055 welds are 245 MPa and 1.5%, 270 MPa and 2.0%, 310 MPa and 5.4%, and 285 MPa and 2.4%, respectively. The tensile strength and elongation of the 1.5 wt.% TiB2-7055 weld were the highest, showing ductile fracture. The developments of new welding wires which consist of TiB2 particles promote additional applications of the spray-formed 7055 aluminium alloy.