چكيده به لاتين
The process of Ablation Casting (AC) is a novel sand casting technique that offers not only the benefits of Conventional Sand Casting (CSC) but also opportunities to overcome some of its shortcomings. This research was conducted in two sections. The purpose of the first section was to evaluate the effect of chemical composition and solidification range of alloy in the AC process. In this section, the variations of the solid fraction parameter at different times of A413 alloy (skin solidification) and A356 alloy (pasty solidification) was investigated through the simulation of the CSC process. Subsequently, the effect of the AC process on these alloys, with two water spraying delay times of 60 and 120 s, was evaluated by considering thermal analysis and microstructural parameters. In the second section, the influence of the AC process on the microstructure and mechanical properties of an aluminum matrix composite reinforced by SiC particles with two volume fractions of 5 and 10% was examined. The CSC simulation process revealed that the alloys with skin solidification like A413 to be more suitable for the AC process. The experimental results of the first section demonstrated that the AC process increased the cooling rate of both alloys (6 and 4 times for A413 and 10 and 9 times for A356) compared to CSC for delay times of 60 and 120 s, respectively. Notably, the AC had a more significant impact on reducing the SDAS in A413 (75 and 60% for delay times of 60 and 120 s) compared to A356 (61 and 45% for delay times of 60 and 120 s), respectively. Additionally, the reduction of the eutectic silicon aspect ratio was nearly equal in both A413 (81 and 77% for delay times of 60 and 120 s) and A356 (83 and 80% for delay times of 60 and 120 s) alloys through the AC process compared to CSC. Due to the greater reduction of the SDAS parameter of A413 compared to A356, it was confirmed that the alloys with skin solidification are more suitable than the alloys with pasty solidification for AC process, and these results confirmed the simulation results. In the second section, the results of the thermal analysis of the aluminum matrix composite with 5 vol% SiC in a sloping pattern showed that the cooling rate in the growth zone of the primary alpha aluminum in the AC process, compared to CSC, for the thicknesses of 30 mm, 50 mm, 70 mm, and 90 mm, was 15, 9, 7, and 3 times, respectively. Moreover, the average cooling rate from the start to the end of solidification in the AC process, compared to CSC, for the thicknesses of 30 mm, 50 mm, 70 mm, and 90 mm, was 36, 19, 13, and 11 times, respectively. The SDAS in the ablated composite with 5 vol% SiC was reduced by 25 to 60% compared to CSC, and by 30 to 63% for the composite with 10 vol% SiC. For both composites (5 and 10 vol% SiC), the variations of the volume fraction of SiC in relation to the distance from the surface showed that, due to the increase in the cooling rate, the particle settling phenomenon occurred less in the AC process than the CSC process, resulting in a more suitable distribution of particles in the AC composites compared to CSC composites from the surface to bottom at different thicknesses. These results were confirmed by decreasing of DP (Distribution Parameter) in AC samples relative to CSC samples. This parameter showed that a more uniform distribution of particles has been obtained by AC process compared to CSC process at different sections of the castings. The results of the tensile testing revealed that the AC process increased the yield strength, ultimate tensile strength, elongation and stiffness parameters of the 5 vol% SiC composite by 53, 50, 59 and 128%, respectively, and by 51, 47, 60 and 122% for the 10 vol% SiC composite, respectively, compared to the CSC process. Examination of the fracture surface indicated that the fracture of the composites could be attributed to shrinkage porosity (especially in the CSC samples) or Fe-containing intermetallic compounds in both CSC and AC samples. Finally, it was observed that the distribution of hardness in the AC process was more uniform from the surface to the bottom compared to the CSC process.
