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High performance of rapid solidified Si-Al alloys
A novel Si-Al alloy was prepared by rapid solidification technology for electronic packaging. After year's of experience and development,the studies outcomes indicate that the alloys (Si-(27%–70%)Al) have advantageous physical and mechanical characteristics, including low coefficient of thermal expansion (7.5 ppm/℃–17 ppm/℃), high thermal conductivity (120–175 W/(m.K)), low density (2.43–2.64 g/cm3), high ultimate flexural strength (180–220 MPa) and Brinell hardness (162–261). The alloys are easy to machine to tight tolerances using standard machine tools and they can be electroplated with gold finishes and soldered with Sn-Pb alloy without any difficulty.
You will please find the below properties of Si-Al alloys:
Aluminum alloys containing highly loaded silicon (Si/Al composite) are of special importance in terms of thermal management applications owing to their low density, high thermal conductivity and tailorable coefficient of thermal expansion (CTE). Besides the attractive physical properties, the strength and elastic modulus of Si is markedly higher than Al , so that highly loaded Si/Al composite may be effectively strengthened and has superior mechanical properties. This proposal is supported by the extensively accepted strengthening theory for particle reinforced Al matrix composites (AMCs). Besides, appropriate strength–toughness combinations will enable the structure–function integrated applications of this lightweight material.
Typically, high volume fraction Si/Al composite often contains 50–75 vol.% Si inclusions in manner of closely packed particles or semi-continuous network within Al matrix. In such kind of AMCs, the coordinated deformation of matrix and particle is difficult because of the intense constraint of reinforcement framework. As a result, these composites are brittle and their mechanical properties become highly sensitive to flaws, such as porosities , particle defects or abnormally coarsened Si particles. Most of the available investigations on Si/Al composites revealed poor mechanical properties and machinability. Particularly, strength of composites reinforced with more than 50% Si is often comparable or even lowered than the non-reinforced Al alloys, and further degrades with increasing Si content. In a word, the mechanical behaviors of this composite are highly dependent on the fabrication processing which now is not well controlled.Si/Al alloy was produced by our proprietory rapid solidification process to reach isotropic and homogeneous microstructure with average grain size is within 40μm,high surface roughness and no macro-segregation,which greatly improve the performance.