The Study Of Heat Treatment Strengthening Mechanism Of Semi-Solid/Hot Extrusion Al-Fe Alloy

Heat treatment T1 and T6 have been applied to Al-Fe alloy after thixoforming and hot extrusion to investigate the effects of heat treatment on microstructure and mechanical properties in this paper, using OM(Optical Microstructures), SEM(Scanning Electron Microscope) and other methods.The results indicated that after semi-solid extrusion, grains were much smaller than those after electromagnetic Stirring, but distributed unevenly on the matrix; the Al3Fe was surrounded by a few Cu elements, and became a slight "halo". After T6 heat treatment, more Cu elements gathered around Al3Fe, which became a visible "halo". In addition, grains were coarsening and irregular-shaped, so the mechanical properties of alloy decreased. While after T1 heat treatment, grains were fine and well-distributed. The mechanical properties of alloy were improved by strengthening phases Al2Cu precipitated out.It is also showed in hot extrusion experiment. After hot extrusion, the mechanism properties of Al-5.5Fe-4Cu-2Zn-0.5Mn-0.4Mg achieved 275.31MPa, increasing about 71%, compared with casting. its mechanism properties also decreased after T6 heat treatment.it is so different from semi-solid formation, after hot extrusion, rich-Cu phases can only be near rich Fe phase, forming sphere typed rich-Cu phase, while after T6 heat treatment, rich-Cu phase became a visible "halo" around Al3Fe, after T1 heat treatment, The mechanical properties of alloy were improved by strengthening phases Al2Cu precipitated out.