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- Microstructural characterization and corrosion-resistance behavior of friction stir-welded A390/10 wt% SiC composites-AA2024 Al alloy jointsPublication . Aval, Hamed Jamshidi; Galvão, IvanThis study examined the effect of traverse speed on the mechanical properties, corrosion-resistance behavior, and microstructure of friction stir-welded A390/10 wt% SiC composites AA2024 Al alloy joints. The laminar flow of both materials was found to diminish in the stir zone (SZ) when the traverse speed of the tool increased from 40 to 80 mm/min, lowering their mixing rate. Large aspect ratio Si particles are broken by the tool pin-induced applied plastic strain, which turns them into refined equiaxed particles. Their aspect ratio remains unchanged in the SZ, despite their decreasing size. SiC and Si particles progressively come into view when moving from the AA2024 alloy’s SZ to the composite workpieces. These changes happen abruptly as traverse speed increases due to the lack of an interfacial layer structure. The advancing side (AS)’s SZ grain size drops from 4.2 ± 0.3 μm to 1.2 ± 0.2 μm as the traverse speed drops from 80 to 40 mm/min. Increased traverse speed from 40 to 80 mm/min will result in a 5.8% decrease in elongation percentage (EP) and 8.4%, 36%, and 10.3% increases in the ultimate tensile strength (UTS), corrosion resistance, and yield strength, respectively.
- Characterization of friction stir welded Al-4Cu-Mg alloy / Al-16Si-4Cu-10SiC composite jointPublication . Aval, Hamed Jamshidi; Galvão, IvanThis study investigated the tool’s rotational speed effect during dissimilar friction stir welding of A390–10 wt.% SiC composite-AA2024 aluminum alloy on microstructure, mechanical properties, and corrosion resistance. The results show that the tunnel defect is created on the advancing side at low rotational speeds of 400 and 600 rpm due to insufficient material flow and a high rotational speed of 1200 rpm due to turbulent material flow in the stir zone. Finely equiaxed recrystallized grains are formed in the stir zone under a high plastic strain rate and particle-stimulated nucleation mechanism. The minimum hardness occurs in the TMAZ of the AA2024 aluminum alloy side, and by increasing the rotational speed from 800 to 1000 rpm, the average hardness in the stir zone decreases from 146.06±8.67 to 137.86±3.98 HV0.1. Also, by increasing the rotational speed from 800 to 1000 rpm, the stir zone’s yield strength and ultimate tensile strength decrease by 4.9 and 5.2%, respectively. With the increased rotational speed from 800 to 1000 rpm, corrosion current increases from 0.0213 to 0.0225 mA.cm_2 and corrosion resistance decreases by 17 %. After friction stir welding with a rotational speed of 800 rpm and traverse speed of 20 mm/min, the corrosion resistance of the joint increases and decreases compared to the composite base metal and AA2024 aluminum alloy base metal, respectively.
- Microstructure and corrosion behavior of A390-10 wt% SiC composite-AA2024-T6 aluminum alloy dissimilar joint: Effect of post-weld heat treatmentPublication . Aval, Hamed Jamshidi; Galvão, IvanThe weldability of aluminum matrix composites to other materials, such as aluminum alloys, is an essential point in expanding the use of these materials. This study investigated the effect of rotational speed and post-weld heat treatment on the microstructure, mechanical properties, and corrosion behavior of A390-10 wt% SiC composite/ AA2024-T6 aluminum alloy dissimilar joint. Friction stir welding is performed using a square frustum pyramid pin tool with a rotational speed of 400–1200 rpm and a traverse speed of 40 mm/min. Results found that a surface groove formed on the weld crown at a rotational speed lower than 800 rpm due to insufficient material flow. Also, the tunnel defect formed on the advancing side at a rotational speed higher than 1000 rpm due to the turbulent flow of material. By increasing rotational speed from 800 to 1200 rpm, the average grain size of the advancing and retreating sides increased by 41.1 and 46.3 %, respectively. Compared to AA2024-T6 and A390-10 wt% SiC composite base metals, the average hardness of the stir zone of the joint fabricated by the rotational speed of 800 rpm increased by 8.4 and 38.2 %, respectively. By increasing the rotation speed from 800 to 1000 rpm, the yield strength and ultimate tensile strength decreased by 6.8 and 6.5 %, respectively. By decreasing rotational speed from 1000 to 800 rpm, the elongation and corrosion resistance decreased by 5.4 % and 34.7 %, respectively. After post-weld heat treatment, the hardness, yield strength, ultimate tensile strength, and corrosion resistance increase 15.9, 12.7, 7.8, and 28.9 %, respectively.
- Evaluation of tool rotational speed effect in Al-16Si-4Cu-10SiC composite/Al-4Cu-Mg alloy jointPublication . Jamshidi Aval, Hamed; Galvão, IvanThis study investigated the influence of the rotational speed of the tool with a cylindrical threaded pin on the microstructure, mechanical properties and corrosion resistance of the Al-16Si-4Cu-10SiC composite/Al-4Cu-Mg alloy joint. The results show tunnel defects are formed on the advancing side in the heat input less than 121 J/mm and more than 342 J/mm. With the increase of rotational speed from 800 to 1000 rpm, the silicon particle size and the aspect ratio have decreased and increased from 5.6 ±1.2 to 3.5±1.4 µm and 0.6 to 0.8, respectively. By decreasing rotational speed from 1000 to 800 rpm, the maximum hardness (152.3 ±0.6 HV0.1), yield strength (383±6 MPa), ultimate tensile strength (469±9 MPa) and corrosion rate (1.03 mm/year) were achieved.