Experimental Investigation of Mechanical and Metallurgical Properties of MIG Brazed Joints

Abstract

ii newlineABSTRACT newlineLightweight vehicle design is an efficient method to achieve environmental and economic goals such as reduction in fuel consumption and environmentally unfriendly gas emissions. Weight of automobiles can be reduced by introducing lightweight materials such as aluminium, magnesium, composites etc. in place of heavier steels and/or by adopting thinner high strength steels. High strength steels with reduced thickness can provide desired strength to the automobile structures along with the profound lightening. Zinc coated steels are used in automobile manufacturing in order to improve the corrosion resistance. High strength steels are composed of specific microstructures which necessitates systematic control over the heat input during joining/welding. In order to preserve the properties of high strength steels, low heat input joining processes are recommended which can effectively control the undesired microstructural evolutions. In addition, loss of zinc coating in the vicinity of joint can degrade the performance of joint in corrosive environments. Furthermore, dissimilar joining i.e. aluminium-steel is an unavoidable practice in automobile manufacturing. Due to solubility limitations between Fe and Al, formation of hard and brittle Fe-Al intermetallic compounds takes place during dissimilar joining which may degrade the mechanical performance of the joint. Therefore, present focus has been to develop alternative low heat input processes for joining thin coated steels sheets as well as dissimilar materials. newlineThe presence of the recently developed CMT process as one of these novel joining processes and its promising implementation in acquiring reliable cost-efficient steel-steel and aluminium-steel dissimilar joints for automotive lightweight design and the consequent lack of information on their performance, raise the necessity of characterizing the mechanical and metallurgical properties of these joints and relating them to their geometrical and microstructural features. Therefore, aim of the present wo