Microstructure and Texture Evolution during Friction Stir Processing of AZ31 Mg Alloy

Abstract

In this study, a well-textured AZ31 Mg alloy sheet was friction stir (FS) processed, and the microstructure and texture evolution in various regions of the processed alloy were examined by optical microscopy (OM) and electron back scatter diffraction (EBSD). The results showed that the grain size in the FS zone was significantly refined compared to that in the base material (BM). The average grain size in the thermomechanically affected zone (TMAZ) and heat-affected zone (HAZ) was comparable with that in the BM. There is a gradual change of local texture from BM to FS zone due to plastic flow together with heating input during the FS processing. The <0002> direction was roughly parallel to the cylindrical pin surface normal of the FS zone. The <0002> direction in the HAZ is similar to that in the BM, but more diffuse. The <0002> direction in the TMAZ was tilted 25~30o away from the ND and there is a distinct boundary between the FS zone and TMAZ at the advancing side which introduced an incompatibility between the FS zone and TMAZ. This might explain the fact that the transverse FS processed Mg alloys commonly fracture at the advancing side during tensile tests.

Effect of welding flash on the corrosion of friction stir spot welded AZ31B

“…Currently, there is no specification for the immersion time that is required to properly evaluate the corrosion rate of a magnesium test coupon. As a result, corrosion rates are measured for a variety of exposure times ranging between several hours and a few weeks . Pardo et al have shown that the estimated corrosion rate for the alloy depends on the time used to expose the coupons to corrosive media .…”

Effect of ZrO2 additions on fabrication of ZrO2/Mg composites via friction-stir processing

“…Therefore, friction-stir processing provides a great possibility to resolve the contradiction between the mechanical properties and damping performance of magnesium alloys. [16][17][18][19][20] ZrO 2 particles have a high melting point and their doping to an alloy can inhibit the grain growth. When the alloy is plastically deformed, ZrO 2 particles are uniformly distributed along the grain boundaries, impeding the movement of dislocations and bending the dislocations deformed around them, promoting the formation of a concentrated deformation zone.…”

Effect of microtexture distribution on inhomogeneous deformation and fracture of friction-stir-processed magnesium alloys

“…Optical microscope (OM), electron backscatter diffraction (EBSD, Oxford Instruments equipped in FEI Nova 400) techniques were used to characterize the microstructure and texture of the specimens. For detailed description on material preparation and characterization methods, please see the previous studies [11,16] . Figure 1 shows that the microtexture is different in the various regions of the FSP specimen due to the different frictional heat and plastic deformation experienced.…”

“…a) overall cross-sectional macrostructure of FSP AZ31 Mg alloy; (b) the (0002) pole figures in various positions of the cross-sections[16] .…”