Browsing by Author "Kumara, B."

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    Effect of Multi-Axial Room-Temperature Forging on Scratch Hardness and Wear Properties of Hypoeutectic Al-7.3Si and Eutectic Al-12.1Si Alloys
    (Springer, 2024) Kumara, B.; Kumar, G.V.P.
    In this work, effect of multi-axial room temperature forging process on scratch and wear characteristics of Al-7.3 and Al-12.1Si alloys with varying cumulative strains was investigated. Al-7.3 and Al-12.1Si alloy ingots were remelted in a furnace and then poured into a preheated die to produce a cast sample of the desired shape and dimension for the MAF process. These samples were subjected to solution heat treatment before forging Scratch test was conducted to measure the scratch resistance of unprocessed and MAF-processed samples. Dry sliding wear tests were performed on a tribometer (pin-on-disk) at ambient temperatures. MAF-processed materials exhibited better scratch and wear resistance compared to as-cast materials. After MAF, wear mechanisms in both alloys shifted from adhesive and delamination wear to a combination of abrasive and a lesser amount of adhesive wear. Moreover, the degree of delamination significantly decreased after MAF-process. Improved scratch and wear resistance is mainly due to increased microhardness via refinement and improved uniformity in the redistribution of eutectic silicon as well as the strain hardening of the aluminum phase. © ASM International 2023.
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    Influence of Multi-directional Room-Temperature Forging Process on Microstructure and Mechanical Behaviour of Eutectic Al-12Si Alloy
    (Springer, 2022) Kumara, B.; Preetham Kumar, G.V.
    In the present work, the influence of multi-directional forging on the microstructure and mechanical behaviour of eutectic Al-12Si alloy at ambient temperature has been examined. The sample for multi-directional forging was prepared by melting and pouring the commercially available LM-6 aluminum alloy ingot into a casting die. Prior to the forging process, the samples were solutionized for 3 h at 525 °C and then cooled in water. Light optical microscopy and scanning electron microscopy were used to examine the microstructure of materials. Microstructural observations have shown that effectively broken coarse needle-shaped plates like silicon particles with an average size of 11.7 µm in length of as-cast samples into fine particles with an average size of 2.8 µm in length after three cycles of forging (9 passes) and are evenly distributed in the α-Al phase. After three cycles, the tensile strength of the as-cast sample is enhanced from 192 to 382 MPa, and its hardness is enhanced from 66.6 to 100.2 Hv, respectively. X-ray diffraction analysis of Al-12Si alloys revealed the existence of α-Al and eutectic silicon (Si) phases. The peak broadening is also noted in X-ray diffraction pattern of three cycles, samples with cumulative strains of 2.43, which confirms the reduction in silicon particle size and grain size. Facets and tearing ridges are observed on the tensile fracture surface of forged samples. The improvement in the mechanical properties of forged samples can be attributed to the evenly distributed silicon particles and the work hardening of the aluminum phase. © 2022, ASM International.
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    Influence of Multi-directional Room-Temperature Forging Process on Microstructure and Mechanical Behaviour of Eutectic Al-12Si Alloy
    (Springer, 2022) Kumara, B.; Preetham Kumar, G.V.
    In the present work, the influence of multi-directional forging on the microstructure and mechanical behaviour of eutectic Al-12Si alloy at ambient temperature has been examined. The sample for multi-directional forging was prepared by melting and pouring the commercially available LM-6 aluminum alloy ingot into a casting die. Prior to the forging process, the samples were solutionized for 3 h at 525 °C and then cooled in water. Light optical microscopy and scanning electron microscopy were used to examine the microstructure of materials. Microstructural observations have shown that effectively broken coarse needle-shaped plates like silicon particles with an average size of 11.7 µm in length of as-cast samples into fine particles with an average size of 2.8 µm in length after three cycles of forging (9 passes) and are evenly distributed in the α-Al phase. After three cycles, the tensile strength of the as-cast sample is enhanced from 192 to 382 MPa, and its hardness is enhanced from 66.6 to 100.2 Hv, respectively. X-ray diffraction analysis of Al-12Si alloys revealed the existence of α-Al and eutectic silicon (Si) phases. The peak broadening is also noted in X-ray diffraction pattern of three cycles, samples with cumulative strains of 2.43, which confirms the reduction in silicon particle size and grain size. Facets and tearing ridges are observed on the tensile fracture surface of forged samples. The improvement in the mechanical properties of forged samples can be attributed to the evenly distributed silicon particles and the work hardening of the aluminum phase. © 2022, ASM International.
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    Investigation on Microstructure and Mechanical Properties of Solution Heat-Treated and Multi Directional Forging-Processed LM-25 Aluminium Alloy
    (Springer, 2020) Kumara, B.; Preetham Kumar, G.V.
    The experimental study of hypoeutectic Al-7.3Si alloy on microstructure and mechanical properties processed by MDF at room temperature was reported in this paper. A commercial LM-25 aluminium alloy ingot was melted in an electric casting furnace and poured into a preheated rectangular casting die. The samples were then solutionized for 10 h at 535 °C and quenched in water for MDF processing. Microstructure analysis of the samples was done with the help of optical microscopy and scanning electron microscopy. Microstructural observation of MDF processed up to six passes sample showed that coarse eutectic silicon particles with an average length of 16 µm are effectively broken into fine particles with an average length of 4 µm and uniformly distributed in aluminium phase. After six passes, UTS of as-cast specimen is increased from 177 to 441 MPa and microhardness is increased from 75 to 127 Hv. XRD analysis of the samples confirmed the presence of Al phase and eutectic Si phase. Therefore, modification of eutectic Si particle with Al phase refinement has been demonstrated to be a very important factor for enhancing mechanical properties of aluminium–silicon alloy. © 2020, The Indian Institute of Metals - IIM.