Microstructure And Mechanical Properties Of Hot Rolled Fe-C-Mn-Si-X Multiphase Steels

The present study is aimed at developing the high strength, high formability low alloy steels having the retained austenite as one of the constituents. The main emphasis has been placed on understanding the effects of processing variables and alloying element (Cu) on the microstructure and properties of hot rolled Fe-C-Mn-Si base alloys. Experimental results show that microstructure of hot rolled alloys consists of ferrite, bainite, martensite and retained austenite, whose volume fraction and morphology vary depending on the hot rolling conditions. Increase in the quench-finish temperature results in a homogeneous distribution of fine granular particles of retained austenite and hard second phases in a ferrite matrix and accordingly a good combination of strength and ductility. addition of Cu results in the precipitation of fine E-CU in ferrite grains, resulting in the increased work hardening at the early stage of deformation. Cu containing alloy has much improved mechanical properties over the base alloy, having UTS of more than 1000MPa and elongation of more than 25%. Based on the results, the optimum microstructure for a better combination of strength and ductility is suggested to be the one having granular particles of retained austenite and hard phase (martensite or bainite) in a fine ferrite matrix.