جستجوی مقالات مرتبط با کلیدواژه "a356" در نشریات گروه "مواد و متالورژی"

This research investigated the cooling curves and tensile test results of three casting methods conventional CO2 sand casting (CSC), ablation casting with a water-soluble binder (ABL), and Ablation casting with Na2SiO3 binder (DWS). With the as-cast CSC samples, the σUTS and εf were 125 MPa and 3%, respectively which were promoted by the DWS process to 193 MPa and 11.5 %, respectively. The ABL process could increase the σUTS and εf to 210 MPa and 19 %, respectively. According to metallography examinations, the SDAS of α-Al dendrites decreased from 80µm in CSC to 40µm in DWS and 20µm in ABL. Ablation with a water-soluble binder had the most effect on tensile mechanical properties as it provided the highest cooling rate (1.2 °C/s) comparing to the two other processes. The differences between these two Ablation procedures were 50% in SDAS and 65% in εf, while 13% with respect to σUTS. Prior researches attributed these enhancements to the α-Al dendrites SDAS affected by the high cooling rate experienced. The DWS results, however, reveal a research gap indicating the participation of other factors besides merely the α-Al dendrites in improvement of the mechanical properties in Al-Si alloys.

In this study, the effect of Ca, Sr, Mn, and Be on modification and quality index ‎improvement of A356 aluminum alloy containing 1.2 wt% Fe impurity was studied in as-‎cast and heat treated conditions. According to the results, Sr and Ca modified the eutectic Si ‎particles and decreased the size of detrimental β-Al5FeSi compounds so that their average ‎size reduced by 23 and 18%, respectively. The addition of Be and Mn did not affect the ‎eutectic Si, but converted the brittle b-platelets to the α-Fe Chinese-scripts. Due to this ‎microstructural variation, the quality index of the alloys modified by Ca, Sr, Be, and Mn has ‎increased by 58, 32, 31, and 17%, respectively. T6 heat treatment led to the precipitation ‎hardening of the alloy, thermally modified the eutectic Si particles, and fractured the b-‎particles. Although, it did not exert significant effect on the size and volume fraction of α-‎compounds. The maximum improvement of quality index in heat-treated samples (36 %) ‎was observed in non-modified base alloy whilst the amplitudes of the quality index ‎improvement in the Ca, Sr, Be and Mn modified samples were 6, 13, 21, and 19 ‎respectively. Increasing of porosity content and the remaining of rather large α-compounds ‎were found to be the most important factors responsible for the relative reduction of the ‎quality index in modified and heat treated samples.‎