Sensitivity analysis for thickness uniformity of Al coating layer in extrusion of Mg/Al clad bar

Abstract

Although Mg alloys possess many attractive properties, the use of Mg alloys has been limited due to their extremely poor corrosion resistance. In the authors’ previous study, they have developed a new process for Mg/Al cladding by hot extrusion with a convex die. In the extrusion process, it was found that the thickness uniformity of the Al coating layer can be controlled by changing the die angle. However, the optimal condition of the extrusion and the influences of extrusion parameters on the coating thickness uniformity remain unclear. In this study, therefore, the sensitivity analysis has been performed in order to evaluate the influences of extrusion parameters on the coating thickness uniformity. The sensitivities of the following five parameters were evaluated: (1) initial thickness of the coating material plate, (2) extrusion temperature, (3) ram speed, (4) die angle, and (5) ratio of simulated flow stress to the experimental one for pure Al. In order to perform the sensitivity analysis, the process for Mg/Al cladding was modeled. The results from the extrusion model fairly agree with the experimental results. Thus, it can be said that the present model of Mg/Al cladding process is reliable. From the sensitivity analysis, it was found that the initial thickness of the coating material plate and die angle influence on the uniformity most. The extrusion temperature, ram speed, and flow stress ratio do not have significant influences.