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Microstructure Evolution of Al-Si-Cu-Mg(-Fe) Alloys by Deformation-Semi Solid Extrusion Process

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Fe is an impurity in some aluminum alloys. Due to the low solid solubility of Fe, Fe-intermetallic compounds (Fe-IMCs) are formed during solidification. The Fe-IMCs degrade the mechanical properties such as ductility since they have platelet and coarse morphologies. It is brittle and acts as a stress raiser on fracture. On the other hand, Fe is a ubiquitous element and Fe-containing alloys can utilize in recycled aluminum alloys. Because we need to consider resources with low cost to produce automotive components environmentally, it is required to investigate Fe-containing alloys for recycling and price. Controlling size and morphology of the Fe-IMCs are becoming an important issue for strong and ductile aluminum alloys.

In this study, a deformation-semi solid extrusion (D-SSE) process was introduced to change the negative effect of Fe-IMCs on the mechanical properties. Microstructure evolution of Al-Si-Mg-Cu(-Fe) alloys by D-SSE process has been investigated by means of optical and scanning electron microscopes (SEM) linked with energy disperse x-ray spectrometer (EDS). Higher deformation rate gives rise to the smaller size of the Fe-IMCs. The Si particles are not affected by the D-SSE process while the Fe-IMCs are finely fragmented. The average size of the Fe-IMCs and Si particles in extruded alloys were 2.6 um and 3.9 um, respectively. Less than 3 um of the Fe-IMCs were distributed on the matrix in the Fe-added alloy. The number of particles increased due to the fragmentation of the Fe-IMCs.

Daehan Kim
Tokyo Institute of Technology
Additional Authors:
  • Dr. JaeHwang Kim
    Korea Institute of Industrial Technology
  • Prof. Equo Kobayashi
    Tokyo Institute of Technology