Investigation of Pre-milling Effect on Synthesis of Ti5Si3 Prepared by MASHS, SHS, and MA

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Ti5Si3 was fabricated by self-propagating high-temperature synthesis (SHS), mechanical-activated SHS (MASHS), and mechanical alloying with the aim of investigating the effect of milling energy on final product. For MASHS process, Ti and Si as starting materials were milled by high energy ball milling, with ball-to-powder weight ratio (BPR) of 10:1, for different times (1, 3, and 6 h), then pressed to form pellets. Green compacts were placed in a tube furnace preheated to three different temperatures of 1000, 900, and 800 °C with argon atmosphere for the synthesis. The milled and synthesized powders were characterized by means of XRD and SEM. The results showed that Ti5Si3 was not formed during milling up to 3 h, after that a trace of Ti5Si3 peaks can be detected from XRD pattern. The increase in milling time prior the combustion reaction caused a decrease in the crystallite size of the final product and ignition temperature of the reactant. The average crystallite sizes of Ti5Si3 after activation of 1, 3, and 6 h were calculated 87, 55, and 48 nm, respectively. Higher milling energy in BPR 15:1, led to the full reaction and formation of nanostructured Ti5Si3 in milling media by mechanical alloying method, even after 1 h. The crystallite sizes of Ti5Si3 after milling of powders from 1, 3, and 6 h, were calculated 70, 26, and 14 nm, respectively. For the SHS process Ti and Si were mixed in the methanol. The combustion reactions were carried out in the tubular furnace and reactor. SEM results showed that Products were formed via MASHS process have more uniformity of microstructure compared to those synthesized via SHS process.