Research On The Microstructure And Technology Of Heat Treatment Of Semi-Solid Formation Al-Fe Based Alloy

Although the Al-5.5Fe-4Cu-2Zn-0.5Mn-0.4Mg alloy has better performance compared with Al-5Fe alloy,a large number of needle-like thick Al₃Fe phases which separate matrix still in the alloy.The semi-solid forming technology has been used to prepare alloy in this issue with the purpose is to thin structure and improve performance of the alloy.The effect of different heat treatment technology on properties of semi-solid formation alloy has been studied to improve mechanical properties of the alloy,then, designs reasonable heat treatment technology system.SEM,TEM,X-Ray have been used to observer microstructure of alloy.Heat treatment strengthening mechanism and precipitation feature of strengthening phase have been analyzed.The experimental results indicate that UTS of Al-5.5Fe-4Cu-2Zn-0.5Mn-0.4Mg alloy increase from 161MPa to 270MPa after semi-solid formation.The UTS of semi-solid formation Al-5.5Fe-4Cu-2Zn-0.5Mn-0.4Mg alloy decrease after T6 heat treatment.The mechanical properties of the alloy are lower than that after semi-solid formation when different T6 heat treatment process.Mechanical properties of alloy are lower and lower with the extension of the solution time.Study have shown that semi-solid formation similar to the strong plastic deformation that lead to re-dissolution of second phase and the role of it is equivalent to warming of heat treatment which lead to grow up of the second phase and lead to decrease of mechanical properties of alloy.The UTS of semi-solid formation Al-5.5Fe-4Cu-2Zn-0.5Mn-0.4Mg alloy have a substantial increase after T1 heat treatment. The tensile strength of alloy reach to the highest value 315Mpa after aged at 160℃for 10h. There are three stages of aging process,the change of elongation and tensile strength of alloy have the same trend.Diffusion-precipitation G.P zone which have sheet structure form in {001} and meta-stable phase are found.G.P zone transformed into meta-stable phaseθ″andθ′which growth in {100}αwith the increase of aging time.The diameter ofθ′is about 200nm.The direct reason that leads to the increase of mechanical properties is precipitation ofθ″phase.θphase which formed when aging at 160℃for 24h have square structure and have not coherence with matrix.