Preparation, mechanical properties, and toughening mechanisms of SiCw/SiCp‐reinforced zirconia‐toughened alumina ceramics

Abstract

Zirconia‐toughened alumina (ZTA) ceramics with high mechanical properties were sintered by hot‐pressing method using SiC particles (SiCp) and SiC whiskers (SiCw) as the reinforcing agents simultaneously. The influences of sintering temperature, SiCp, and SiCw contents on the microstructure and mechanical properties of ZTA ceramics were investigated. It was found that both SiCp and SiCw could contribute to grain refinement significantly and promote the mechanical properties of the ceramics. However, the excess addition of SiCp or SiCw led to the formation of pores with large sizes and degraded the mechanical properties instead. When 13 wt% SiCp was introduced, the maximum flexural strength of 1180.0 MPa and fracture toughness of 15.9 MPa·m1/2 were obtained, whereas the maximum flexural strength of 1314.0 MPa and fracture toughness of 14.7 MPa·m1/2 were achieved at 20 wt% SiCw. Interestingly, the simultaneous addition of SiCp and SiCw could further improve the mechanical properties, and the highest flexural strength of 1334.0 MPa and fracture toughness of 16.0 MPa·m1/2 were achieved at a SiCw/SiCp ratio of 16/4. The reinforcement mechanisms in the ceramics mainly included the phase transformation toughening of ZrO2, the crack deflection and bridging of SiCp and SiCw, and the pull‐out of SiCw.

Mechanical properties and strengthening mechanism of SiC particle reinforced porcelain

“…However, at higher SiC contents, the flexural strength decreased, likely because excess SiC caused a thermal expansion mismatch between the matrix and SiC, leading to excessive internal residual stress, causing micro-cracks inside the porcelain to cause defects. [25][26][27] temperature and holding time markedly influenced the flexural strength, and this trend is related to that of the bulk density, as shown in Figures 1 and 2. At excessively high low or high firing temperatures and holding times, the porosity of the porcelain and the bulk density increased; however, the bulk density and flexural strength decreased.…”

“…When the SiC content was 8 wt%, the flexural strength reached its maximum value of 122 ± 4 MPa, which is 90.6% higher than that of the matrix (64 ± 5 MPa). However, at higher SiC contents, the flexural strength decreased, likely because excess SiC caused a thermal expansion mismatch between the matrix and SiC, leading to excessive internal residual stress, causing micro‐cracks inside the porcelain to cause defects 25–27 …”

High damage tolerant Al2O3 composite ceramics constructed with short Al2O3 fibers

“…Lots of effort has been made to alleviate the brittle failure of ceramic materials. Such as phase change toughening, [3][4][5] particle dispersion toughening, 6,7 whisker toughening, [8][9][10] long fiber toughening, 11,12 and bionic structure toughening 2,13,14 developed to overcome the sensitivity to defect. Among them, the long fiber toughening and bionic structure composite ceramics achieve the optimal nonbrittle failure manner with high toughness and work of fracture together with considerable strength.…”