Abstract
In this study, the effects of squeeze casting process and T6 heat treatment on the microstructure and mechanical properties of 2017A aluminum alloy were investigated with scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), differential scanning calorimetry (DSC), and microhardness and tensile tests. The results showed that this alloy contained α matrix, θ-Al2Cu, and other phases. Furthermore, the applied pressure and heat treatment refines the microstructure and improve the ultimate tensile strength (UTS) to 296 MPa and the microhardness to 106 HV with the pressure 90 MPa after ageing at 180°C for 6 h. With ageing temperature increasing to 320°C for 6 h, the strength of the alloy declines slightly to 27 MPa. Then, the yield strength drops quickly when temperature reaches over 320°C. The high strength of the alloy in peak-aged condition is caused by a considerable amount of θ′ precipitates. The growth of θ′ precipitates and the generation of θ phase lead to a rapid drop of the strength when temperature is over 180°C.
Highlights
IntroductionDue to their excellent mechanical and physical properties, Al-Cu cast alloys are used in automobile and military industries, aerospace, and in applications such as floor beams, engine pistons, wing box, covers, brake components, fuel tanks, slot tracks wheel, fittings, fuel systems, body skin connectors [1,2,3]
Due to their excellent mechanical and physical properties, Al-Cu cast alloys are used in automobile and military industries, aerospace, and in applications such as floor beams, engine pistons, wing box, covers, brake components, fuel tanks, slot tracks wheel, fittings, fuel systems, body skin connectors [1,2,3].the major problems in casting these alloys consist in their high tendency to form casting defects such as hot tearing, solidification shrinkage, porosity [2], and their bad fluidity in conventional casting processes. ese problems have negative effects on the mechanical properties and have greatly limited the application of Al-Cu cast alloys
Souissi et al [9] have shown that squeeze casting caused the refinement of the microstructure and reduction in the dendrite arm spacing (DAS) of the cast structure possibly due to increasing the cooling rate of 2017A aluminum alloy. ey found that the gravity cast specimens have the lowest ultimate tensile strength (UTS) compared with the squeeze cast specimens
Summary
Due to their excellent mechanical and physical properties, Al-Cu cast alloys are used in automobile and military industries, aerospace, and in applications such as floor beams, engine pistons, wing box, covers, brake components, fuel tanks, slot tracks wheel, fittings, fuel systems, body skin connectors [1,2,3]. Maleki et al [11] have investigated considerably the effects of squeeze casting parameters on the microstructure and mechanical properties of aluminum alloys. A typical precipitation hardening treatment involves three steps: (1) the solution treatment that brings all the elements into solid solution state; (2) rapid quenching in order to avoid diffusion and to retain supersaturated solid solution at room temperature; and (3) ageing treatment to form fine precipitates by controlled decomposition of metastable supersaturated solid solution In this regard, Panuskova et al [12] have investigated the effects of the heat treatment solution of Al-Si-Cu cast alloys on the microstructure of the alloy in three aspects, namely, the dissolution of coarse Al2Cu, homogenization of the microstructure, and improvement of eutectic silicon morphology (fragmentation, spheroidization, and coarsening). A Micro-Vickers hardness analysis HV was performed employing a MEKTON Vickers Hardness Tester with a diamond pyramidal indenter. ree measurements were taken at randomly selected points with a load of 300 g applied for 30 s
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