Friction stir processing

About: Friction stir processing is a research topic. Over the lifetime, 2977 publications have been published within this topic receiving 62158 citations.

Multi-pass submerged friction stir processing of AZ61 magnesium alloy: strengthening mechanisms and fracture behavior

Abstract: Multi-pass submerged friction stir processing (M-SFSP) with an overlapping ratio of 50% was applied on as-cast AZ61 magnesium plate. The relationship between the microstructure and tensile behavior of the M-SFSP plate was investigated. With the cooling enhancement during processing, the grain size is significantly refined to be ~ 3.7 ± 1.7 μm in the stir zone. The initial network-like β-Mg17Al12 second phase in the cast alloy is effectively fragmented and dissolved into magnesium matrix, as revealed by a consistent right shift of magnesium peaks in the XRD patterns due to the lattice shortening caused by the smaller aluminum atoms getting into magnesium matrix to form substitutional solid solution. Texture is modified with a lower intensity in the center of stir zone than at the top surface. Compared with the base material, the strength and ductility of the M-SFSP Mg plate are significantly improved, mainly due to grain refinement along with dislocation strengthening and solid solution strengthening. Despite texture weakening, the M-SFSP plate still exhibits mechanical anisotropy to a certain extent, depending on the initial texture and loading direction. Cracking is observed to initiate from the transitional zone and propagate along the microstructural band due to the presence of high local residual stresses.

Effect of inhomogeneous deformation on anisotropy of AZ31 magnesium sheet

Abstract: Inhomogeneous plastic deformation in AZ31 magnesium sheet has been studied during uniaxial tensile testing using digital image correlation and electron backscatter diffraction techniques. Large strain gradients develop on the sheet surface parallel and perpendicular to the loading direction while very little deformation occurs in the thickness direction. This lack of thinning leads to an abrupt fracture following the development of a premature but extensive diffuse neck but without any localized neck. The strain distribution on the sheet surface evolves nonlinearly with strain, impacting the measured plastic strain ratio, r-value. The results show that r-value should be measured at “points” rather than over the “gage length” in Mg alloys. Friction stir processing modifies the basal texture and thus significantly improves the forming limit for in-plane plane strain path.

Different strategies of secondary phase incorporation into metallic sheets by friction stir processing in developing surface composites

Abstract: Friction stir processing (FSP) is a solid-state processing method, which recently gained wide popularity to modify the microstructure of metallic surfaces and to produce surface composites. For the past decade, composites of different materials such as aluminum, copper, magnesium, titanium, and their alloys were successfully produced by FSP. The amount of secondary phase that is dispersed at the surface of the workpiece during FSP and the level of dispersion depend on many factors such as tool design, processing parameters, and type of material. Recently, the method of secondary phase incorporation into the surface metals was also considered as an important factor in developing surface composites by FSP. A few strategies such as groove filling, holes filling, sandwich method, direct method, and surface coating followed by FSP methods have been developed as promising ways of secondary phase incorporation into the surface of the materials during FSP. The aim of this review paper is to give a comprehensive summary of different methods developed to disperse the secondary phase into the surface of the workpiece during FSP to produce surface composites. The strategies have been explained, compared, and discussed to suggest an appropriate method based on the requirement to adopt in developing surface composites.