Abstract
Due to its excellent comprehensive performances, Al-Si-Mg alloy i widely used in automotive, transportation and other fields. In this work, tensile performances and fracture behavior of Al-Si-Mg alloy modified by dilute Sc and Sr elements (Al-7.12Si-0.36Mg-0.2Sc-0.005Sr) were investigated at the temperature of −60–200 °C for the first time, aiming to obtain a satisfactory thermal stability within a certain temperature range. The results showed that the new designed Al-Si-Mg alloy possessed a completely stable yield strength and a higher-level elongation under the present conditions. Fracture morphology analysis, fracture profile observation and strengthening mechanism analysis were applied to elucidate the evolution mechanisms of yield strength and elongation of the alloy. The fracture modes were significantly distinct in different temperature sections, and the reasons were discussed. In addition, the interaction among the nano precipitate phase particles, the deformation substructure and the dislocations were responsible for the thermal stability of the alloy within a certain temperature range.
Highlights
In the past few decades, due to its lightweight, excellent mechanical performances, good corrosion resistance and castability, hypoeutectic Al-Si casting alloy, especially Al-Si-Mg alloys, were widely used in automotive engines, high-speed train sleepers and other transportation fields [1,2,3]
Tzeng et al investigated the effect of dilute Sc and Be elements on the thermal stability of Al-7Si-0.6Mg alloy, and the results showed that precipitation of fine Al3 Sc particles effectively inhibited grain growth and suppressed dislocation movement, leading to a better thermal stability at the thermal exposure temperature of 250 ◦ C [15]
Qiu et al investigated the effect of Sr and La elements composite modification on the mechanical performances of Al-Si-Mg alloy; the results indicated that Sr can promote the more isotropic growth of eutectic Si and convert the morphology of eutectic Si from acicular-like to short fibrous or fine particles, which promoted the mechanical performance of the alloy [1]
Summary
In the past few decades, due to its lightweight, excellent mechanical performances, good corrosion resistance and castability, hypoeutectic Al-Si casting alloy, especially Al-Si-Mg alloys, were widely used in automotive engines, high-speed train sleepers and other transportation fields [1,2,3]. Previous research showed that due to the stability of Al3 Sc phase at elevated temperatures, Sc is arguably known as one of the most attractive and effective microalloying elements to develop high-performance aluminum-based alloy for high temperature applications [2,12]. Xu et al performed Sc and Sr elements composite modification and T6 treatment on Al-Si-Mg alloy, focused on the mechanical properties at room temperature and obtained satisfactory UTS (296 MPa) and El. Though Sc element can improve the high temperature performances of Al-Si-Mg alloy, few literatures focused on the effect of a wide range of temperature variations on the YS stability. The results indicated that the alloy possessed satisfactory YS stability over a wide temperature range, and the reasons were discussed through fracture behavior analysis, microstructure observation and strengthening mechanism analysis
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