Semi-solid manufacturing process of magnesium alloys by twin-roll casting

Abstract

An experimental approach has been employed to ascertain the effectiveness of semi-solid roll strip casting of magnesium alloys by a twin-roll caster. The demand for light-weight products with high strength has grown recently due to the rapid development of automobile and aircraft technology. One key to such development has been utilization of magnesium alloys, which can potentially reduce the total product weight. However, the problems of utilizing magnesium alloys are still mainly related to high manufacturing cost. One of the solutions to this problem is to develop magnesium casting–rolling technology in order to produce magnesium sheet products at competitive cost for commercial applications. In this experiment, magnesium alloys AZ31B, AZ91D, AM50A and AM60B were used for twin-roll strip casting. Temperature of the molten materials and roll speeds of upper and lower rolls, which could be adjusted independently, were varied to find appropriate manufacturing conditions. Effects of cooling and contact condition on possible forming were clarified in terms of contact condition between molten material and the rolls. Microscopic observation of the crystals of the finished casting was performed. It has been found that 2.0–3.0mm thick magnesium sheets could be produced at a speed of 25m/min. It has been found that the hot rolled cast magnesium sheets produced by semi-solid manufacturing process could be used for plastic forming.