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Abstract
The feasibility of enhancing the thermal conductivity of an alloy via microstructural refinement was examined using Al–12%Si alloy as a model material. Al–12Si alloy samples were fabricated at different process parameters using laser engineered net shaping (LENS™) and the effect of microstructural features on the thermal conductivity was studied and compared with conventionally cast alloy. The large difference in melting points and laser light absorptivities of Si and Al as well as the low melt viscosity of Al–12Si alloy resulted in a very small process window to successfully fabricate bulk Al–12Si alloy samples using LENS™. Comparison of microstructural features of laser-processed samples with cast Al–12Si alloy showed significant refinement in eutectic Si for laser processed samples. Microstructural refinement not only improved the thermal conductivity of Al–12Si alloy but also compensated the detrimental effect of porosity on thermal conductivity. The thermal conductivity of cast alloy varied between 82 and 93 W/mK, which is ∼21–76% lower than the values exhibited by laser-processed samples in the range 103–153 W/mK. The results of LENS™ fabrication, microstructural evolution and thermal properties of Al–12Si alloy bulk structures can be extended to other immiscible alloys and metal matrix composites for a variety of engineering applications.
Acknowledgements
The authors acknowledge the financial support from National Science Foundation (CMMI 0728348) and the Office of Naval Research (N00014-05-0583). We also acknowledge financial support from the WSU Research Foundation under gap funding. Also, the financial support from the W. M. Keck Foundation to purchase a LENS™-750 system at Washington State University is acknowledged.