Effects of whisker-like β-Si3N4 seeds on phase transformation and mechanical properties of α/β Si3N4 composites using MgSiN2 as additives

• Published in: Ceramics international 2013-04, Vol.39 (3), p.2743-2751
• Main Authors: Liang, Zhen-hua, Zhang, Hai-long, Gui, Liu-cheng, Li, Jun, Peng, Gui-hua, Jiang, Guo-jian
• Format: Article
• Language: English
• Subjects: A. Phase transformation; Beta; C. Mechanical properties; D. Silicon nitride; Deflection; Elongation; Fracture toughness; Hardness; Mechanical properties; Seeds; Silicon nitride
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2012.09.041

α/β Si3N4 composites with β-Si3N4 content ranging from 26% to 100% were hot-pressed with or without β-Si3N4 seeds, using MgSiN2 as additives, and their mechanical properties were investigated. When the α-Si3N4 content was over 58%, the microhardness of α/β Si3N4 composites was in the range of 23–24GPa, and then the indentation hardness decreases with decreasing the content of α-Si3N4, whether with β-Si3N4 seeds or not. The toughness increased with increasing elongated β-Si3N4 grains, which improved fracture resistance by crack bridging, pull out or the crack deflection mechanism, and reached the maximum value of 7.0MPam1/2 with 1wt% β-seeds. In comparison with α/β Si3N4 composite with a similar phase composition, the fracture strength was improved by adding β-Si3N4 seeds because of the relatively smaller grain sizes and higher toughness. The α/β Si3N4 composite with 5wt% β-seeds showed a high strength of 1253MPa, a high hardness of 20.9GPa and a toughness of 6.9MPam1/2.