Effect of Al Additions on the Synthesis of Single-Phase Ti 3 SiC 2
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Effect of Al Additions on the Synthesis of Single-Phase Ti3SiC2 ZhengMing Sun1,3, Songlan Yang1,2, Hitoshi Hashimoto1 and Michel W. Barsoum3 1
National Institute of Advanced Industrial Science and Technology (AIST), Nagoya 463-8560, Japan
2
State Key Laboratory for Corrosion and protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, P. R. China
3
Department of Materials Science and Engineering, Drexel University, Philadelphia, PA19104, U.S.A.
ABSTRACT Powder mixtures of 3Ti/SiC/C/xAl with different Al contents (x=0~0.2) were reactively sintered by pulse discharge sintering (PDS) process, to reveal the effect of Al addition on the single-phase bulk Ti3SiC2 synthesis. It was found that the optimal sintering temperature for the Ti3SiC2 synthesis is greatly decreased by the Al addition. Almost single-phase bulk Ti3SiC2 material can be synthesized from 3Ti/SiC/C/0.15Al and 3Ti/SiC/C/0.20Al powder mixtures at temperature as low as 1200OC for 15 min by PDS. And the optimal temperature range for the Ti3SiC2 formation is enlarged obviously by the Al addition. INTRODUCTION Ti3SiC2 is the most extensively studied MAX ternary compounds (viz. Mn+1AXn where, M: early transition metal, A: group A element, X: C and/or N, n=1-3). The MAX phases have received added attention recently due to their unique combination of both metal- and ceramiclike properties. In the case of Ti3SiC2, it is thermally and electrically conductive, damage tolerant, thermal shock resistant and readily machinable. Furthermore, its density is relatively low (4.5g/cm3) and it is stable up to at least 1700OC in inert atmospheres and vacuum. Ti3SiC2 was firstly synthesized via chemical reaction in 1967 [1]. Reactive sintering process for the single-phase bulk Ti3SiC2 material synthesis seems rather difficult by applying various starting powder mixtures, including Ti/Si/C [2], Ti/SiC/C [3,4] as well as Ti/Si/TiC [5-7], using different sintering technique, such as arc-melting , HIP or SHS-HIP , reactive sintering. Generally, TiC will exist in the final product together with Ti3SiC2. In our previous work, bulk material with high content of Ti3SiC2 (over 99 vol.%) was rapidly synthesized from Ti, Si, and TiC powder mixtures with molar ratios of 2:2:3 by PDS technique at 1300OC for about 15min [5-7]. It should be pointed out that the high-temperature oxidation
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resistance of Ti3SiC2 is questionable [8] due to the formation of TiO2 rich scale after long-term high temperature exposure, and Al is an interesting element for the alloy oxidation resistance improvement based on the possible formation of protective Al2O3 scales. In addition, the low melting point (about 660OC) of Al enables the formation of a melting pool during the sintering, which may accelerate the corresponding element diffusion and should be helpful for the Ti3SiC2 formation. In the present report, powder mixtures of 3Ti/SiC/C with different Al additions were used for reactive sintering by PDS process, to reveal the effect of Al addition on the s
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