Process variable optimization in the cold metal transfer weld repair of aerospace ZE41A-T5 alloy using central composite design

Abstract

The pulsed cold metal transfer (CMT+P) process was evaluated for the repair of aerospace structural components made from ZE41A-T5 magnesium alloy. The choice of welding variables was considered to be unique for the material type, weld design and geometry, and application-specific requirements. A design of experiment (DOE) method based on a rotatable 3D central composite design (CCD) was used to systematically establish relationships between independent welding variables and the resultant output variables of the CMT+P process, including the development of mathematical models based on second-order polynomial. A multiple response desirability function approach was then used for process optimization. The CMT+P process produced high-quality welds in the alloy. Welding process variables were established to produce desired weld penetration and weld reinforcement and complete fusion with minimal weld defects. Optimal domains of the independent variables were achieved; where the welds comply with the application-specific (repair of gearbox housing) requirements and acceptable class A weld quality of the aerospace fusion welding standard AWS D17.1.