A novel micro-rolling&incremental sheet forming hybrid process:Deformation behavior and microstructure evolution

Thin-walled metal parts with functional micro-featured surface have broad application prospects in the fields of resistance reduction,noise reduction,etc.In this study,a novel micro-rolling&incremental sheet forming hybrid process(μR-ISF)is proposed to fabricate thin-walled metal parts with microgroove arrays.An analytical model which relates the rolling force and microgroove depth in the micro-rolling stage was first established.Then,the formation mechanism of microgroove morphology during both micro-rolling stage and macro-shape forming stage are investigated.After the micro-grooved sheet being incrementally formed,a significant reduction(between 21%to nearly 60%)is occurred in the depth of both transverse and longitudinal grooves compared to the flat sheet.Meanwhile,the width of transverse grooves decreases slightly by about 10%on average,while the width of longitudinal microgrooves increases significantly by more than 30%on average.After micro-rolling,85°{102}tensile twins appear on the micro-grooved sheet and the percentage of 65°{112}compressive twins increases.After incremental forming,the percentage of low-angle grain boundaries and the density of geometrically necessary dislocations in the formed part increase significantly,and the grain size distribution becomes more uniform.The present work provides a new strategy for the fabrication of 3D metal thin-walled components with surface micro-features.