Microstructures and mechanical properties of heat-treated Al-5.0Cu-0.5Fe squeeze cast alloys with different Mn/Fe ratio

摘要

The Al-5.0 wt% Cu-0.5 wt% Fe alloys with different Mn/Fe ratio were prepared by squeeze casting. Various test techniques, including tensile test, image analysis, scanning electron microscope (SEM), X-ray diffraction (XRD), electron probe micro-analyzer (EPMA) and transmission electron microscopy (TEM) were used to examine the microstructures and mechanical properties of the alloys in T5 heat-treated condition. The results show that the beta-Fe (Al7Cu2Fe) is stable and its needle-like morphology is maintained after T5 heat treatment. However, the Chinese script AlmFe, alpha-Fe or Al-6(FeMn) partially transform to a new Chinese script Cu-rich alpha(CuFe) (Al7Cu2Fe or Al7Cu2(FeMn)), which is harmful to the mechanical properties of the alloys due to the decrease of the Cu content in alpha(AI) matrix. The optimal Mn/Fe ratio is determined by the morphology of Fe-rich intermetallics, volume fraction of theta' and T (Al20Cu2Mn3), size of alpha(Al) dendrite and porosity. Excessive Mn/Fe ratio will deteriorate the mechanical properties of the alloys due to the increase of the total amount of porosity and the Fe-rich intermetallics. When the Mn/Fe ratio is 1.6 and 1.2 for the applied pressure of 0 MPa and 75 MPa, respectively, the needle-like beta-Fe phase is completely converted to the Chinese script Fe-rich intermetallics. The ultimate tensile strength, yield strength and elongation of the T5 heat-treated alloy with the Mn/Fe ratio of 1.2 and applied pressure of 75 MPa reach 395 MPa, 335 MPa and 14%, respectively. 2013 Elsevier B.V.

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