Effect of Heat Treatment on the Microstructure and Mechanical Properties of a Composite Made of Al-Si-Cu-Mg Aluminum Alloy Reinforced with SiC Particles

Abstract

In this paper, the effect of heat treatment (solution treatment and artificial aging) on the microstructure and properties of as-cast Al5Si1Cu0.5Mg aluminum alloy and its composite reinforced with 1.5 wt.% SiC particles was studied. The results showed that at 520 • C the optimal solution time for the aluminum alloy and its composite is 9 h and 6 h, respectively. After solution treatment, the microstructure of these two materials consists of a uniform distribution of nearly spherical eutectic Si and skeletal γ phase, furthermore, the composite eutectic Si phase is smaller and γ phase is more dispersed. After artificial aging at 175 • C for 6 h, the microstructure of the composite is more dispersed and finer than that of the aluminum alloy on the whole and Al 2 Cu is precipitated. After heat treatment, the microhardness, ultimate tensile strength, and elongation of the aluminum alloy and its composite are higher than those of the as-casts. At the same time, the morphology of tensile fracture surface changes very much from a large area of cleavage plane to a large number of dimples and the tearing ridges become thicker for both the aluminum alloy and its composite.Metals 2019, 9, 1205 2 of 10 intermetallic phases, such as Al 2 Cu, some phases containing copper and magnesium elements, and for changing the morphology of eutectic silicon phase; (ii) quenching, usually at room temperature, to obtain a supersaturated solid solution; (iii) age hardening, namely, the precipitation of different types of precipitated phases such as Mg 2 Si, Al 2 Cu and Al 5 Mg 8 Si 6 Cu 2 from the supersaturated solid solution either at room temperature (natural aging) or at an elevated temperature (artificial aging). During T6 heat treatment, many researchers [7,10,11] found that solution time, aging time, aging temperature, and some other parameters have a great influence on the microstructure and properties of aluminum alloys. For example, Costa et al. [7] found that for a directionally solidified Al-Si-Cu alloy, the profile of secondary dendrite arm spacing values obtained along the length of the DS casing increased only when the solution time adopted in the T6 heat treatment was increased from 5 to 8 h. They also found that the samples heat treated with a solution time of 8 h exhibited a decrease in hardness when compared to that of samples subjected to a solution time of 5 h, which may be associated with the corresponding increase in the dendritic arm spacing, coarsening of Si particles, and collapse of tertiary dendritic arms that makes the dendritic network less complex. Ceschini et al. [11] found that the hardness, yield strength, and ultimate tensile strength of as-cast CAl5Si1Cu0.5Mg alloy, the chemical composition of which is similar to that of Al5Si1Cu0.5Mg alloy, were obviously reduced after overaging treatment, which was mainly caused by the coarsening of precipitated phases in the crystal. Thus, it is of importance to select the parameters of heat treatment to improve microstructure and mechanical properties of aluminum alloy...

Effect of chemical composition and T6 heat treatment on microstructure and mechanical properties of a hyper eutectic Al–Si alloy

“…After heat treatment, the ultimate tensile strength (UTS)increased from 104.39 to 143 KN (improved by 37.17%) while the hardness increased from 56.13 to 78.80 HRB (improved by 40.38%). The increase in UTS and HRB was due to the precipitation of phases such as Mg2Si and the strong interfacial bonding strength of the Al-Si eutectic phase (Singh et al, 2016;Li et al, 2019).…”

“…Cyclic semi-solid heat treatment changed the morphology of iron-rich intermetallic phases to be plate-like and fine plate iron-rich intermetallic phases instead of needle-like iron-rich intermetallic phases observed in as-cast samples. Li et al (2019) studied the effect of heat treatment (solution treatment and artificial ageing) on the microstructure and properties of as-cast Al 5Si1 Cu 0.5Mg aluminium alloy and composite reinforced with 1.5 wt% SiC particles. Results showed that the optimal solution time for the aluminium alloy and its composite was 9 and 6 hours respectively.…”

Structure and Surface Property of Carbon Films Deposited on Cemented Carbide by Electron Cyclotron Resonance Plasma Sputtering

“…Fabrication of carbon film is a hot topic nowadays, and many of the methods are achieved to prepare carbon film, such as, filtered cathodic vacuum arc (FCVA) [1], pulsed plasma-enhanced chemical vapor deposition (PECVD) [2], pulsed laser deposition (PLD) [3] and so on. ECR plasma sputtering system makes the deposition of carbon film under low temperature and low energy possible, it is also effective for attaining high quality carbon films via electron irradiation or ion irradiation.…”

An Overview of the Interactions Between Reinforcements and Al Matrices with Si, Cu And Mg as Alloying Elements in Aluminum Matrix Composites: Case of Oxide Reinforcements

“…For MMSF characteristics of the hollow reinforcements such as porosity percentage and wall thickness also affect the mechanical properites 45 . Among the most reported reinforcements for AMC are carbides (SiC, B 4 C, WC, TiC) [46][47][48][49][50][51][52] , oxides (Al 2 O 3 , SiO 2 , TiO 2 , ZrO 2 , Y 2 O 3 , MgO, CeO 2 ) [53][54][55][56][57][58] , nitrides (Si 3 N 4 , BN) [59][60][61] and Carbon Nanotubes (CNTs) [62][63][64][65][66][67] . For the case of syntactic foams there have been mainly reported metallic or ceramics hollow spheres, being Fe, SiC, SiO 2 and Al 2 O 3 the most used [40][41][42][43][44][45][68][69][70][71][72] .…”