Texture, Microstructure and Hardness on Magnesium Alloy AZ31 Surfaces Processed by ECASD

P. RISSO; M. AVALOS; R. BOLMARO; P. FERNANDEZ MORALES; E. MENDOZA FANDIÑO; V. TARTALINI

Cancún

Congreso; XXV International Materials Research Congress; 2016

MRS

Mg alloys have attracted high interest because of its outstanding specific strength. Automobile and airplane industries are constantly improving the strength-to-weight ratio of their structural materials. Particularly AZ31B alloy (Mg + 3 wt.% Al, 1 wt.% Zn and 0.2?0.5 wt.% Mn) has achieved a large diffusion with those purposes. Mn addition helps on the refinement of microstructure conferring an improvement on mechanical properties. Meanwhile, grain size reduction by Severe Plastic Deformation (SPD) has been also widely applied to improve mechanical properties. Among the many SPD techniques, the one known as Equal Channel Angular Sheet Drawing (ECASD) is appropriate to introduce large deformations on the Surface of materials, without changing the section of the material, except for a small section reduction. The main purpose of the technique is the production of sheets with very large surface hardness with a ductile core while expending just small amounts of extra deformation energies.The current work presents the results on AZ31B sheets subject to 2, 4, and 6 passes using two shearing conditions of ECASD at various temperatures (25ºC, 100ºC and 200º). Textures were determined by laboratory X-ray diffraction and EBSD. EBSD allows the evaluation of the evolution of crystal sizes in function of the distance to the surface and the presence of twinning. Twinning is evident by the analysis of the textures, which show mainly two components, one due to the spin induced by the shearing of ECASD and the other one direct product of twinning.Tensile tests and Microhardness, by Knoop tests on the lateral face of the sheets, were performed, allowing the determination of the influence of SPD on the hardness from surface to surface going through the center of the sheet. Almost 50% increase on hardening, with respect to the non-processed material was obtained near to the surface after 6 passes. Larger numbers of passes were not as effective as a hardening technique as in the first 2 passes.