Abstract
RSA 905, a rapidly solidified aluminum alloy, has been widely utilized in optical, automotive, and aerospace industries owing to its superior mechanical properties such as hardness and strength compared to conventional aluminum alloys. However, the surface finishing of RSA 905 to achieve submicron surface roughness is quite challenging and was rarely addressed. This paper presents an experimental and analytical study on magnetic field-assisted finishing (MFAF) of RSA 905 through a systematic investigation on surface integrity in relation to the MFAF process parameters. The effect of abrasive and polishing speed conditions on material removal and surface roughness was quantitatively investigated. The surface and subsurface quality were evaluated by optical microscope and scanning electron microscope (SEM) observations, residual stress measurement, surface microhardness and tribology test. The results show that relatively high material removal and low surface roughness were obtained under conditions using the SiC abrasive with a grit size of 12 µm at polishing speed of 400 rpm or using the Al2O3 abrasive with a grit size of 5 µm at polishing speed of 800 rpm. Heat melt layer caused by wire electrical discharge machining (EDM) during the sample preparation was removed by MFAF without inducing new subsurface damage. The MFAF process also helps release the surface residual stress and improve the tribological performance although the surface microhardness was slightly reduced.
Highlights
Material property and function are intimately dependent on microstructure such that ultra-fine grained (UFG) materials are in general harder, tougher and more wear-resistant compared to their coarse-grained versions [1]
The results show that relatively high material removal and low surface roughness were obtained under conditions using the SiC abrasive with a grit size of 12 μm at polishing speed of 400 rpm or using the Al2O3 abrasive with a grit size of 5 μm at polishing speed of 800 rpm
The surface and subsurface quality was evaluated by optical microscope and scanning electron microscope (SEM) observations, residual stress measurement, surface microhardness and tribology test
Summary
Material property and function are intimately dependent on microstructure such that ultra-fine grained (UFG) materials are in general harder, tougher and more wear-resistant compared to their coarse-grained versions [1]. Rapid solidification technology (RST) has played a key role in enhancing the mechanical behavior of metallic systems through producing ultra-fine microstructures, especially for lightweight metal alloys since the 1980s [10]. Solidified aluminum, owing to its superior mechanical properties of hardness and strength over conventional light-weight aluminum alloys, has a wide application in optical, automotive, aerospace and even sports industries. As a superior alternative material for injection mold inserts, RSA 905 with an average grain size of 1–2 μm has been developed by the rapid solidification process. The grain size of rapidly solidified aluminum is much smaller than that of the conventional aluminum alloy. In terms of physical and mechanical properties, RSA 905 contains more constituent elements such as Fe, Ni and Cu, and has the same density with the conventional aluminum alloy but about two times higher tensile strength, yield strength, and hardness [11]
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