Microstructure evolution and mechanical properties of ultrafine grained IF steel via multipass differential speed rolling

Abstract

The microstructural evolution and mechanical properties of ultrafine grained interstitial free steel fabricated by multipass differential speed rolling (DSR) technique were investigated. A series of DSR operations were performed up to four passes under a roll speed ratio of 1 : 4 for lower and upper rolls. Microstructural observations using a transmission electron microscope showed that the deformed microstructure comprised the severely deformed ferrite grains with a mean size of y0?7 mm having a relatively high dislocation density. In addition, the nearly equiaxed grains were effectively formed due to the sample rotation of 180u around the transverse axis between each passage where the macroscopic shearing was reversed. Electron backscattered diffraction analysis revealed an increase in the fraction of the high angle grain boundaries in the severely deformed samples with increasing number of DSR operations. The mechanical properties were also examined utilising microhardness and tensile tests, and these were discussed in relation to the shearing and microstructural characteristics.

Study on Deep Drawing Behavior of the Interstitial Free Steel in Correlation With the Microstructure

“…In addition, these materials can be easily coated, painted and welded. These properties make IF steel suitable to be applied to the exterior panels of the automotive body [2][3][4]. These steels are characterized by containing micro alloying elements such as titanium and/or niobium, among other elements that remove the carbon from the matrix, promoting the precipitation of different carbides, nitrides and carbonitrides (of Ti and Nb).…”

“…In addition, crystallographic texture represents another factor that influences the material drawability aptitude. Fibers γ {ND // <111>} are suitable for deep drawing, while the presence of α fibers {RD // <110>} could adversely affect on the sheets forming [4,5]. Different methods are used to evaluate the drawability of alloys through mechanical tests in order to obtain knowledge about the mentioned behaviour.…”

Effect of Grain Refinement and Dispersion of Particles and Reinforcements on Mechanical Properties of Metals and Metal Matrix Composites through High-Ratio Differential Speed Rolling

“…Based upon applications and capabilities, several SPD techniques have been invented, such as equal channel angular pressing (ECAP) [ 5 , 6 , 7 , 8 ], high pressure torsion [ 9 , 10 , 11 ], three roll planetary milling or screw rolling (SR) [ 12 , 13 , 14 , 15 ], accumulative roll bonding [ 16 , 17 ], multi directional forging [ 18 , 19 , 20 , 21 ] and asymmetric rolling (ASR) [ 22 ] or differential speed rolls (DSR) [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. However, for the production of ultra-fine equiaxed grains, severe, complex and high stress is required, and therefore material size is limited for most of the techniques.…”

Ti/Al Multi-Layered Sheets: Differential Speed Rolling (Part B)

“…For ESR, shear deformation is restricted to the near surface region [8,9]. In the case of DSR, the volume that is affected by shear is strongly material dependent as shown in numerous studies on different materials, e.g., steel, copper, aluminium and niobium [3,[10][11][12][13][14][15]. Special attention is paid to the investigation of DSR of hexagonal metals such as magnesium [4,[16][17][18] and titanium [6,[19][20][21].…”