Development of Rheocasting Facility and Production of Mg - Based Composites

Abstract

Work on rheocasting process, a molten alloy is vigorously stirred either continuously during solidification or isothermally in the semi-solid state followed by pouring. The vigorous agitation results in formation of globular or spheroidal primary morphology. Advantage of rheocasting is well known viz. grain refinement due to breakage of dendrites during stirring, reduced porosity rendering high strength, better die life in die-casting due to pouring at comparatively lower temperature etc. This process was developed in MIT (USA) in 1971 and subsequently lot of development has been taken place with respect to method of particle addition, stirrer design, control of process parameters, application areas etc. During the last three decades this process has gained popularity for MMCs preparation. Although composite can be prepared by many other processes viz. PM technique, spray forming, in-situ process, infiltration technique, squeeze casting etc, however there is a unique advantage of rheocasting. Till to-date enormous amount of work has been done on Al-MMCs, but Mg- based composites are meagre. Mg-base MMC due to its light weight and higher strength to weight ratio is being preferred to Al-base MMC in certain areas of aerospace & automobile applications.