The repeated thermal shock behaviors of a ZrB2.pdf

Int. Journal of Refractory Metals and Hard Materials 29 (2011) 44–48 Contents lists available at ScienceDirect Int. Journal of Refractory Metals and Hard Materials j ourna l homepage: www.e lsev ie / locate / IJRMHMThe repeated thermal shock behaviors of a ZrB2–SiC composite heated by electric resistance method Songhe Meng, Fei Qi ?, Hongbo Chen, Zhi Wang, Guanghui Bai Center for Composite Materials, Harbin Institute of Technology, Harbin 150001, China? Corresponding author. Tel./fax: +86 451E-mail address: hitqifei@ (F. Qi). 0263-4368/$ – see front matter ? 2010 Elsevier Ltd. Al doi:10.1016/j.ijrmhm.2010.06.012a b s t r a c ta r t i c l e i n f oArticle history: Received 15 April 2010 Accepted 24 June 2010 Keywords: ZrB2-based ceramic Microstucture Repeated thermal shocks Mechanical propertiesRepeated thermal shocks of ZrB2–20 vol.% SiC (ZrB2–SiC) composite was investigated by the electric resistance method with 330 A and 4 V. It was found that the maximum temperature of the specimen center was obtained in 20 s and the specimen was cooled down to room temperature in 10 s due to a coolant system, and then the specimen was heated again. The thermal shock treatment increased the flexural strength with a peak at 20 cycles. Even though 30 cycles showed the minimum strength, it was still higher than that of the unshocked specimen. The increase in the strength was attributed to the formation of the oxide layer and the compression stress that resulted from volume expansion upon conversion of ZrB2 and SiC, to ZrO2, B2O3 and SiO2.. l rights reserved.? 2010 Elsevier Ltd. All rights reserved.1. Introduction Zirconium diboride (ZrB2) based ultrahigh temperature ceramic matrix composites are a leading candidate as potential materials for a variety of high temperature structural applications, such as thermal protection structures for leading edge parts on hypersonic reentry space vehicles at over 1800 °C [1–3]. It is primarily because ZrB2 has an excellent combination o