Abstract
Open-porous MAX phase skeletons from Ti3SiC2 were manufactured by Microwave-Assisted Self-propagating High-temperature Synthesis (MASHS) and subsequently subjected to squeeze casting infiltration with an Al-Si lightweight casting alloy (EN AC-44200). This alloy was chosen due to its high flowability, corrosion resistance and good machinability. The manufactured composites, together with a reference sample of the original alloy, underwent testing of thermal properties, including thermal conductivity and diffusivity, specific heat and thermal expansion in the temperature range 50-500 °C, which corresponds to the expected working temperatures of the material. The fabricated AlSi/Ti3SiC2 composites have significantly increased thermal stability, with coefficients of thermal expansion (approximately 10-11 × 10−6 °C−1) half that of the original alloy. As regards mechanical properties, the instrumental Young’s modulus and Vickers hardness of the composite materials are 170.8 and 8.5 GPa, respectively. Moreover, the microstructure and phase composition, structural defects and potential impacts between constituents of the manufactured composites were characterized using SEM, TEM and STEM microscopy and EDS and XRD analysis.
Highlights
Titanium silicon carbide (Ti3SiC2) is composed of Si atoms separated from each other by three Ti layers that accumulate C atoms around them (Ref 1)
The fabrication of an open-porous structure of a MAX preform, with sufficient conversion of the substrates and the strength required for pressure infiltration, involves the determination of parameters for the Microwave-Assisted Self-propagating High-temperature Synthesis (MASHS) synthesis
As SiC particles are far less reactive than the Al or TiC phases, for example, that are present in the Ti-Al-C combination, it is necessary to apply coupled MASHS synthesis
Summary
Titanium silicon carbide (Ti3SiC2) is composed of Si atoms separated from each other by three Ti layers that accumulate C atoms around them (Ref 1). The interesting properties of Ti3SiC2 arise precisely from its crystal structure, in which metallic, covalent and ionic bonds are present Like metals, it possesses high thermal conductivity (34 W mÀ1 CÀ1) and electrical conductivity (4.5 9 106 S/m), good machinability with conventional tools, high resistance to crack propagation, and outstanding resistance to varying ambient operating temperatures (Ref 2). It possesses high thermal conductivity (34 W mÀ1 CÀ1) and electrical conductivity (4.5 9 106 S/m), good machinability with conventional tools, high resistance to crack propagation, and outstanding resistance to varying ambient operating temperatures (Ref 2) Like ceramics, it is characterized by high mechanical strength at elevated temperatures, a low coefficient of thermal expansion—resulting in increased dimensional stability of machine parts made from it—a high melting point, good corrosion and oxidation resistance, a high modulus of. Being a good thermal conductor with a low coefficient of thermal expansion, it is a promising alternative to materials commonly used for working at high temperatures, such as bushings, brake disks and heat exchangers (Ref 4)
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