Enhanced tensile and bending yield strengths of 304 stainless steel and H62 brass by surface spinning strengthening

Abstract

In this work, the tensile and bending yield strengths of 304 stainless steel and H62 brass are effectively enhanced by surface spinning strengthening (3S) that can introduce a strengthening layer with gradient microstructure on the samples. The results show that the two metals exhibit distinct grain refinement in the top layer as well as severe grain deformation in the subsurface layer with obvious gradient characteristics. For the tensile yield strength, it increases from 336 MPa to 372 MPa for 304 stainless steel, and 280 MPa–294 MPa for H62 brass, respectively. For the bending yield strength, it increases from 581 MPa to 667 MPa for 304 stainless steel, and 496 MPa–523 MPa for H62 brass, respectively. A two-phase (soft and hard phases) structure for the surface strengthened metals is proposed to analyze the enhancement of the tensile yield strength, and the enhancement of tensile yield strength is determined by the maximum microhardness and the thickness of the hardened layer. The enhancement of bending yield strength may be attributed to the maximum microhardness and the corresponding nano-scale grains in the topmost layer. Based on the results above, the tensile and bending yield strengths can be improved and optimized by constructing the gradient microstructure with different grain refinement and microhardness distributions.