Micro incremental forming of thin SS304 foils and its microstructural study

Abstract

Micro-forming of thin foils is challenging due to the size effect, friction effect, and tool design. The conventional macro-forming techniques cannot be directly applied to the thin foils. The incremental forming process (ISF) can be used for thin foils since it possesses higher formability compared to the conventional process. Hence, µ-ISF (micro incremental forming process) experiments were conducted on thin foils of SS304 stainless steel having 50, 100, and 200 µm thickness. As-received foils were further annealed at 950°C with a holding time of 20 mins to achieve strain-free microstructure. The Taguchi L18 orthogonal was applied to optimize the initial processing parameters for, µ-ISF experiments. Using the initial optimized parameters µ-ISF experiments were performed for all the thickness sheets up to the maximum wall angle. It was observed that the higher tool diameter and the lower step depth give the minimum roughness value in the deformed sheet. The tearing mode of failure was observed due to the formation of strain-induced martensite in the deformed sheet. The microstructure and bulk texture analysis relate the orientation and twin fraction with the deformation behaviour. From the texture evolution, it was observed that the brass {110} <112>, Cube {100} <001>, and goss {110} <001> texture component has a greater influence on the formability of SS304 stainless steel thin foils.