DEVELOPMENT OF ALUMINIUM ALLOY BY CLADDING WITH STEEL

Abstract

Technological advance has increased the demand for materials sharply. Uniform metals can not meet the demand so that composite /materials are .required. Among the composite materials, technology of clad -materials' is often found to be cheap and versatile. Clad materials are more useful than uniform materials in many cases since they have characterstics of both materials.. Clad materials have found extensive applications in diversified fields of. industry, defence and aerospace. Stainless steel clad aluminium is used for cooking utensi-les and has considerable potential in cryogenic field.. These also find application in automobile industry for the manufacturing of components like connecting rods, cylinderblock, bearings etc, due to their reduced weight and hence reduced -inertia forces. In the present investigation, the emphasis is given on the cladding of aluminium by stainless steel or by mild steel. Different techniques of cladding such as cold rolling, hot rolling and cast- -cladding technique were carried out. The plates of chose-n dimension of stainless steel and aluminium base alloy were machined to suitable size. Firstly the cold rolling was carried out by sandwitching the aluminium plate in between to stainless steel plate and then tying them with mild steel wire. No bonding was reported after rolling. Then the plates were heated to a temperature of 5000C and maintained at this temperature for I hr, prior to rolling. These plates were then rolled and no bonding was reported. Same procedure was followed by increasing the temperature to 550°C and maintaining at this temperature for 1•hr., prior to rolling. Agai.i no bonding occurred. Technique of hot roll cladding was also applied for the mild steel plate. In this mild steel plate was heated to 800° C and maintained at this temperature for 1 hr prior to rolling. Then this plate was layered with aluminium alloy plate •which was at room temperature and rolled. No bonding was reported because of presence of thick oxide layer on the surface of mild steel `plate. Further cast-cladding technique was carried out. A furnace for casting was constructed by using kanthal wire and master alloy was prepared. This alloy was analysed by wet analysis to know the percentages of Cu, Fe and Si. The casting was taken by.fixing the stainless steel plate in the mould and pouring the molten aluminium alloy at 700° C in to the mould. Samples of suitable size were cut and polished for metallography studies.. .Metallographic studies were also carried out for samples having wires of stainless steel and mild steel, reinforced in matrix of aluminium alloy and annealed at 500° C" of 40 hr. Interface thickness was measured and microhardness were determined at various regions across the reaction interfaces. Thickness of interface was non uniform, which shows that the perfect mechanical contact is necessary for bonding. The high value of hardness 336 VHN and 290 VHN shows the, presence of brittle intermetallic compound at the interface. .-