TY - JOUR
T1 - The effect of heat-treatment on the performance of submicron SiCp-reinforced α-β sialon composites
T2 - III. Mechanical properties
AU - Liu, Q.
AU - Gao, L.
AU - Yan, D. S.
AU - Mandal, H.
AU - Thompson, D. P.
PY - 1997/2
Y1 - 1997/2
N2 - Agglomerate-free SiCp-reinforced Ln-sialon (Ln=Nd and Yb) composites were fabricated by hot-pressing and by pressureless sintering to evaluate the improvement in microstructure and mechanical properties that could be achieved by incorporating sub-micron SiC particles into a sialon matrix and then inducing α → β sialon transformation by heat-treatment. Both Nd2O3 and Yb2O3 were successful in producing dense samples by hot-pressing, but Yb2O3 produced a more stable α-sialon phase than Nd2O3. As a result, Yb-sialon/SiCp composites showed higher hardness (Hv), attributable to the higher percentage of α-sialon grains (formed in acicular morphology) in these materials. Under comparable heat-treatment conditions, the α-sialon phase present in Nd-sialon/SiCp composites was very unstable and almost completely transformed to β-sialon, with the aluminium-containing melilite phase (M') forming at pockets in grain junctions as the dominant grain-boundary phase. Even though the Nd-densified samples contained a large proportion of β-sialon, the fracture toughness(KIc) was not significantly improved by SiCp addition because of the decrease in aspect ratio and the coalescence of grains caused by the longer heat-treatment which resulted in degradation of mechanical properties, especially KIc.
AB - Agglomerate-free SiCp-reinforced Ln-sialon (Ln=Nd and Yb) composites were fabricated by hot-pressing and by pressureless sintering to evaluate the improvement in microstructure and mechanical properties that could be achieved by incorporating sub-micron SiC particles into a sialon matrix and then inducing α → β sialon transformation by heat-treatment. Both Nd2O3 and Yb2O3 were successful in producing dense samples by hot-pressing, but Yb2O3 produced a more stable α-sialon phase than Nd2O3. As a result, Yb-sialon/SiCp composites showed higher hardness (Hv), attributable to the higher percentage of α-sialon grains (formed in acicular morphology) in these materials. Under comparable heat-treatment conditions, the α-sialon phase present in Nd-sialon/SiCp composites was very unstable and almost completely transformed to β-sialon, with the aluminium-containing melilite phase (M') forming at pockets in grain junctions as the dominant grain-boundary phase. Even though the Nd-densified samples contained a large proportion of β-sialon, the fracture toughness(KIc) was not significantly improved by SiCp addition because of the decrease in aspect ratio and the coalescence of grains caused by the longer heat-treatment which resulted in degradation of mechanical properties, especially KIc.
UR - http://www.scopus.com/inward/record.url?scp=0042262674&partnerID=8YFLogxK
U2 - 10.1016/s0955-2219(96)00102-1
DO - 10.1016/s0955-2219(96)00102-1
M3 - Article
AN - SCOPUS:0042262674
SN - 0955-2219
VL - 17
SP - 593
EP - 598
JO - Journal of the European Ceramic Society
JF - Journal of the European Ceramic Society
IS - 4
ER -