Available online at www.sciencedirect.com Journal of the European Ceramic Society 31 (2011) 217–224 Mechanical properties of low temperature synthesized dense and fine-grained Cr 2 AlC ceramics S.B. Li a,b,∗ , W.B. Yu a , H.X. Zhai a , G.M. Song b , W.G. Sloof b , S. van der Zwaag c a Institute of Materials Science and Engineering, School of Mechanical and Electronic Control Engineering, Beijing Jiaotong University, Beijing 100044, China b Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands c Novel Aerospace Materials Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands Received 20 May 2010; received in revised form 6 August 2010; accepted 10 August 2010 Available online 17 September 2010 Abstract Mechanically activated hot-pressing technology was used to synthesize a fine-crystalline Cr 2 AlC ceramic at relatively low temperatures. A mixture of Cr, Al and C powders with a molar ratio of 2:1.2:1 was mechanically alloyed for 3 h, and then subjected to hot pressing at 30 MPa and different temperatures for 1 h in Ar atmosphere. The results show that a dense Cr 2 AlC ceramic with a grain size of about 2 m can be synthesized at a relatively low temperature of 1100 ◦ C. The synthesized fine-grained Cr 2 AlC has a high density of 99%, which is higher than the 95% density for the coarse-grained Cr 2 AlC (grain size of about 35 m) as synthesized by hot pressing unmilled Cr, Al and C. The flexural strength, fracture toughness and Vickers hardness of the fine-grained Cr 2 AlC were determined and compared with the values for the coarse-grained Cr 2 AlC. © 2010 Elsevier Ltd. All rights reserved. Keywords: Cr 2 AlC; Carbides; Mechanically activated hot pressing; Microstructure; Mechanical properties 1. Introduction MAX phase ceramics (where M denotes an early transition metal, A is an element mostly in IIIA or IVA group, and X is either C or N) exhibit many unusual combinations of attractive properties such as a high electrical conductivity, a low oxi- dation rate, resistance against corrosion, and high strength at high temperature as well as good machinability. 1,2 Moreover, these materials show autonomous crack healing at high tem- peratures in an oxidizing environment. 3 Out of the total MAX phase family, the systems Ti 3 SiC 2 , Ti 3 AlC 2 and Ti 2 AlC have been studied extensively because of their attractive properties and relative ease of fabrication. Recently it has been shown that Cr 2 AlC has an even better oxidation and corrosion resistance than Ti 3 SiC 2 and Ti 3 AlC 2 at high temperatures. 4–6 So, Cr 2 AlC is expected to be a more promising candidate for high tempera- ture applications. In addition, the thermal expansion of Cr 2 AlC ∗ Corresponding author at: Institute of Materials Science and Engineering, School of Mechanical and Electronic Control Engineering, Beijing Jiaotong Uni- versity, Beijing 100044, China. Tel.: +86 10 51685554; fax: +86 10 51685554. E-mail address: shbli1@bjtu.edu.cn (S.B. Li). is 12–13 × 10 −6 /K, which is close to that of the superalloys. 7,8 Hence Cr 2 AlC has potential applications in the field of ceram- ics/metals joining and protective coatings on the superalloys. The possibility of depositing large area Cr 2 AlC coatings on steel substrates has already been demonstrated. 9 There are several methods used to produce Cr 2 AlC bulk ceramics. For example, Manoun et al. 10 synthesized Cr 2 AlC bulk ceramic by hot isostatic pressing (HIP) of a mixture of 2Cr/Al/C elemental powders at 1200 ◦ C under 100 MPa for 12 h. Lee and Nguyen 6 obtained Cr 2 AlC bulk ceramic by hot pressing powders of CrC 0.5 and Al at 1300 ◦ C under 25 MPa for 1 h. No information was provided on the presence of other phases. Lin et al. 11 made Cr 2 AlC bulk ceramic with 95% density and con- taining Al–Cr phase as an impurity by hot pressing a mixture of 2Cr/1.05Al/C at 1400 ◦ C under 30 MPa for 1 h. Tian et al. 12 fab- ricated Cr 2 AlC bulk ceramic with Cr 7 C 3 as the impurity by hot pressing a mixture of 2Cr/1.1Al/C at 1400 ◦ C under 30 MPa for 1 h. They 13 also fabricated the ceramic by pulse discharge sinter- ing (PDS) the same mixture at 1250 ◦ C under 50 MPa for 30 min. Impurities of Al 2 O 3 and Cr 7 C 3 were detected in the matrix. Generally, it is difficult to produce a pure Cr 2 AlC ceramic from a mixture of Cr, Al and C powders, due to the formation of intermediate compounds, such as Al 4 C 3 , Cr 7 C 3 and Cr–Al 0955-2219/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jeurceramsoc.2010.08.014