SBIR Phase I: Novel Casting Process for Developing a Carbon Modified Hyper-Eutectic Aluminum-Silicon Alloy for Forging Wear Resistant Parts

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This Small Business Innovation Research Phase I project proposes to develop a 20-25% Si alloy based on the 4032 aluminum forging alloy composition that has low density and high wear resistance. The proposed Phase I research builds upon carbon dispersion in the melt that can increase machinability and fluidity of cast aluminum alloys. To achieve these advantages in hyper-eutectic alloys, it is proposed to adjust the carbon and copper contents in the aluminum alloy during melt processing, and to precipitate during solidification equiaxed particles of primary silicon, carbides and graphite flakes in the Al-Si eutectic. These micro- and nano-particles will provide for higher wear resistance, modulus and toughness. There are significant challenges in this research including the possibility of precipitation of undesired acicular silicon, unacceptable shrinkage, hydrogen embrittlement, segregation etc. during ingot solidification. The high silicon content can significantly reduce solidification and homogeniezation kinetics during processing making it hard to achieve uniform properties and microstructure. Since this research aims to create a new alloy composition using a novel casting process, it will generate considerable new fundamental knowledge in solidification and deformation processing. The broader impact/commercial potential of this project is that a new market will open up to higher-integrity machinable forged hyper-eutectic parts that are heat treatable. Currently, most aluminum-silicon alloy components are limited to cast structures where their strength and wear capabilities override the additional costs of testing for physical defects, rejections, and high costs of machining. Applications in automotive engines include pistons, cylinder heads and connecting rods where wear resistance and light weight is important, and computer equipment manufacturing where thermal properties, weight and rigidity are critical.