In today’s scenario, the fuel cost and stricter norms related to environmental protection are exponentially increasing and thus lightweight forging is gaining importance which directly enhances the efficiency of the entire vehicle leading to reduction in pollution and fuel consumption. Material substitution with lighter alloy is one of the solutions but the part design is a constraint to implement this approach in structural load bearing parts which undergoes dynamic loading in its lifecycle. Mixture forging is a solid / Semi solid hot-forming process of two different materials while plastic deformation occurs. In mixture forging of steel-aluminum parts there is a formation of intermetallic phases and the diffusion occurs between two materials. This paper is addressing the challenges in forging process and especially producing bimetal product by adapting to currently followed forging practices and infrastructure. In this study, a component forging process is designed using finite element computation tool and then forged in two stages followed by application of mixture forging concept during forging operation to achieve light weighting. The two different materials used are 42CrMo4 steel for high strength at the outer case and AA6061 aluminium alloy for a lightweight core. The thickness of the intermetallic phase seam achieved is less than 10 μm and its material characterisation is carried out using SEM analysis. Micro-hardness measurement was taken of the intermetallic phase and is found to be 855 (HV 0.01) which is brittle in nature. The component thus forged is found to be 27% lighter than the component produced by steel forging. This technology is a part of the multi material joining technology using forging process wherein conventional equipment can be used. The bulk forming process achieving multi material solution is a innovative process and can lead to lighweighting of various circular parts and shaft primarily in the transmission of ICE and Electric Vehicles.
Dr. Ajeet Babu Parasumanna, The Automotive Research Association of India, INDIA