Microstructure and mechanical properties of Ti 3 (Al,Ga)C 2 /Al 2 O 3 composites prepared by in situ reactive hot pressi
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ISSN 2226-4108 CN 10-1154/TQ
Research Article
Microstructure and mechanical properties of Ti3(Al,Ga)C2/Al2O3 composites prepared by in situ reactive hot pressing Yuan FANG, Xiaohua LIU, Yuxia FENG, Jianfeng ZHU*, Wei JIANG School of Material Science and Engineering, Shaanxi Key Laboratory of Green Preparation and Functionalization for Inorganic Materials, Shaanxi University of Science and Technology, Xi’an 710021, China Received: July 22, 2020; Revised: September 15, 2020; Accepted: September 26, 2020 © The Author(s) 2020.
Abstract: In this study, Ti3(Al,Ga)C2/Al2O3 composites were successfully synthesized by in situ hot pressing at 1350 ℃ for 2 h using Ti, Al, TiC, and Ga2O3 as raw materials. X-ray diffraction and scanning electron microscopy were used for characterizing the phase identities and microstructures of the sintered composites. The dependence of the Vickers hardness and flexural strength on the Al2O3 content was found to be in single-peak type. Ti3(Al0.6,Ga0.4)C2/10.3vol%Al2O3 composite exhibited significantly improved mechanical properties. Vickers hardness and flexural strength of the composite reached 6.58 GPa and 527.11 MPa, which were 40% and 74% higher than those of Ti3AlC2, respectively. Formation of solid solution and incorporation of second phase of Al2O3 resulted in the opposite influence on the fracture toughness. Finally, the hardening and strengthening mechanisms were discussed in detail. Keywords: Ti3AlC2; solid solution; ceramic composites; microstructure; mechanical properties
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Introduction
Mn+1AXn phases, in short MAX phases, are a class of ternary layered compounds, where M represents transition metal elements, A represents A-group elements (mostly III A and IV A), and X denotes carbon or nitrogen element [1–4]. Theoretically, the bonding in MAX phase is metallic-covalent-ionic in nature, which was calculated by ab initio pseudopotential method based on density functional theory [5,6]. The coexistence of three types of chemical bonds indicates that these compounds have features of both metals and ceramics. For example, they have electrical and thermal conductivity, ductility, and machinability similar to * Corresponding author. E-mail: [email protected]
metals. At the same time, some of the compounds have high melting point, high specific strength, and elastic modulus similar to ceramics [7]. Ti3AlC2 is an important Al-containing member of MAX phase which exhibits several remarkable properties. For example, Ti3AlC2 has excellent oxidation properties when exposed to oxidizing environments, due to the formation of a highly passivating and continuous alumina layer [8,9]. Tzenov and Barsoum [10] showed that Ti3AlC2 did not deform like a metal when it was cut with a high-speed steel knife, even without the use of coolant and lubricant, and only micro-flaking occurred. Moreover, they also reported that Ti3AlC2 has high thermal stability when the temperature is above 1600 ℃; it behaves plastically and shows a high compressive strength under compression deformation. However, He et al. [
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