An investigation of toughening in NiAl composites reinforced with yttria-partially stabilized zirconia particles

Abstract

The results of an investigation of toughening mechanisms in NiAl composites reinforced with yttriapartially stabilized zirconia polycrystals are presented. Different yttria stabilization levels in the zirconia, between 0 and 6 mole pct are employed. It is shown that substantial improvements in fracture toughness are obtained in all the composites reinforced with partially stabilized zirconia particles. The phase contents and microstructures of the composite systems are characterized by X-ray diffraction and transmission electron microscopy (TEM) techniques. Crack tip deformation was also studied using crack tip TEM analysis, and laser Raman spectroscopy was used to estimate the size of the transformation zone. The results show that transformation toughening is significant only in the 2 mole pct yttria-stabilized zirconia composite. Toughening is also shown to occur via slip phenomena within the NiAl grains in the near-tip regions of the composites reinforced with 2, 4, or 6 mole pct yttria-stabilized zirconia particles.

Influence of non-reactive particles on the microstructure of NiAl and NiAl–ZrO2 processed by thermal explosion

“…This high mechanical reinforcement is attributed to an increase in dislocation density induced by prestraining NiAl at high temperature. This mechanism of dislocation induced plasticity has been also highlighted for NiAl-PSZ [28] and NiAl-Al 2 O 3 [29] composites using transmission electron microscopy. Therefore, it is possible that a similar prestraining effect of the NiAl matrix results from the residual stresses generated during the reactive process and improves significantly the mechanical properties.…”

ZrO2 Matrix Toughened Ceramic Material‐Strength and Toughness

“…[ 118,119 ] In addition to the toughening mechanism mentioned in Figure 8a, adding dispersed metal particles can also prevent grain growth during the sintering process, thus achieving the effect of grain refinement. [ 120 ]…”

Thermo-mechanical response of heterogeneous materials with randomly distributed transforming particles

“…The phenomenon of transformation toughening in zirconia composites has been studied by Ramasundaram et al (1998). Inducement of high stress in composites is one of the transformation toughening mechanisms.…”

“…The material properties are shown in Table 3. From the experimental data obtained by Ramasundaram et al (1998), the transformation zone height was observed to be 300 lm, and the volume fraction of particles that undergo stress-induced transformation was estimated to be 35% inside the transformation zone.…”

“…The high stress concentration around a crack tip induces the transformation of particles, and, as a crack propagates, the transformed particles behind the crack tend to close the crack. this transformation-toughening mechanism has been examined experimentally (Ramasundaram et al (1998)), theoretically (Budiansky (1983), Evans and Canon (1986)) and numerically (Ramakrishnan et al (1991), Okada et al (1992)). In this work, a ®nite element approach for the discrete modeling of transformation toughening is presented.…”