Tensile behaviour of gas pressure sintered silicon nitride in the 1600–1700°C temperature range

• Published in: Acta materialia 2001-10, Vol.49 (17), p.3589-3596
• Main Authors: Testu, S, Rouxel, T, Besson, J-L
• Format: Article
• Language: English
• Subjects: Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides); Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; High temperature; Materials science; Mechanical properties; Other materials; Physics; Specific materials; Structural ceramics
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/S1359-6454(01)00250-6

The tensile behaviour of a silicon nitride ceramic has been studied between 1600 and 1680°C under strain rates from 6×10−6 to 1.2×10−5 s−1. At low temperature and/or high strain rate, the behaviour was essentially brittle: failure occurred by cavitation along boundaries of acicular grains lying normal to the tensile axis and linking of these cavities by interfacial debonding. At 1650°C, the deformation started to be ductile: a stress peak was observed in the tensile curve and cavities formed at multigrain junctions while grain boundary sliding began to occur. As the temperature increased, the contribution of grain boundary sliding to deformation increased at the expense of the cavitational component. The stress peak is interpreted in terms of a relaxation effect that governs the competition between cavitation and grain boundary sliding. Le comportement en traction d'une céramique de type nitrure de silicium a été étudié entre 1600–1680°C sous des vitesses de chargement de 6×10−6 à 1.2×10−5 s−1. A basse température et/ou forte vitesse, le comportement est fragile: la rupture est produite par cavitation le long des joints de grains des cristaux aciculaires orientés perpendiculairement à l'axe de traction et jonction de ces cavités par décohésion interfaciale. A 1650°C, le comportement commence à être ductile: un pic de contrainte apparaı̂t sur la courbe de traction et des cavités se forment aux jonctions multiples tandis que des glissements aux joints de grains commencent à se produire. A température croissante, la contribution à la déformation du glissement aux joints de grains augmente au détriment de la contribution cavitationnelle. Le pic de contrainte est interprété comme un effet de relaxation qui gouverne la compétition entre cavitation et glissement aux joints de grains.