DEVELOPMENT OF SPECIAL ALUMINIUM ALLOYS AND PREMIUM QUALITY CASTINGS FOR SPECIFIC APPLICATIONS

摘要

The successful development of two Al alloys, one with rare earth addition for electrical conductor applications using both commercial(IC) and electrical(IE) conductor grade Indian aluminium and another for premium quality cast components for space applications using an Indian Al Si-Mg alloy containing Fe as an impurity (comparable to the French alloy AS7G in terms of structure and properties, both in cast and heat treated conditions) is described. Addition of alloying elements, such as rare earth, to both commercial (IC) and electrical (IE) conductor grade has resulted in improved electrical conductivity of more than 1.5 percent and 1 percent IACS, respectively. This improvement has been attributed to the scavenging effect of alloying additions and the formation of intermetallics. Premium quality castings of varying sizes and configuration have been made using Al-12Si alloy (100Nos) and Al-Si-Mg alloy(35Nos). Use of appropriate casting design, melt controls and casting techniques has enabled the latter castings exhibiting comparable qualities of imported ones as well as surpassing the pressure tightness specification requirement. Similarly, two sets of three components each using Al-Si-Mg alloy have been developed to substitute Ti alloy forgings for space application. These castings were found to be of acceptable quality exhibiting the required mechanical properties at room, high (373-503K) and cryogenic (77K) temperatures and hence can effect weight saving.