“…As a result, a decrease in penetration depth as observed in Figure 5 is frequently associated with an increase in nanohardness of a material. 43 Figure 5.The Nanoindentation force-depth curves of the sintered samples at varying ZrO 2 contents.…”
Ni-Cr-ZrO2 composites with varying amounts of ZrO2 additive (5 wt%, 7.5 wt%, 10 wt% and 12.5 wt%) were fabricated using spark plasma sintering method at a sintering temperature of 1000°C, heating rate of 100°C/min, holding time of 5 min, and a pressure of 50 MPa. The effect of ZrO2 addition on the microstructure, tribological and mechanical properties of the developed composites were studied. The results showed that maximum densification was attained at 10 wt% ZrO2. Further increase in the fractions of ZrO2 within the composites results in a decrease in the relative density of the sintered composite. A significant increase in hardness from 433.24 HV to 510.11 HV and elastic modulus from 252.67 GPa to 294.6 GPa was observed in the fabricated samples as the ZrO2 content increase from 5 to 12.5 wt%. An appreciable improvement in the wear performance of the sintered samples was obtained with increasing ZrO2 content. The observed improvement in the properties of the sintered composites was attributed to the presence of the hard dispersoids of ZrO2 and formation of solid solution strengthening and hard Cr3Ni2 phases within the matrix of the sintered composites.
“…As a result, a decrease in penetration depth as observed in Figure 5 is frequently associated with an increase in nanohardness of a material. 43 Figure 5.The Nanoindentation force-depth curves of the sintered samples at varying ZrO 2 contents.…”
Ni-Cr-ZrO2 composites with varying amounts of ZrO2 additive (5 wt%, 7.5 wt%, 10 wt% and 12.5 wt%) were fabricated using spark plasma sintering method at a sintering temperature of 1000°C, heating rate of 100°C/min, holding time of 5 min, and a pressure of 50 MPa. The effect of ZrO2 addition on the microstructure, tribological and mechanical properties of the developed composites were studied. The results showed that maximum densification was attained at 10 wt% ZrO2. Further increase in the fractions of ZrO2 within the composites results in a decrease in the relative density of the sintered composite. A significant increase in hardness from 433.24 HV to 510.11 HV and elastic modulus from 252.67 GPa to 294.6 GPa was observed in the fabricated samples as the ZrO2 content increase from 5 to 12.5 wt%. An appreciable improvement in the wear performance of the sintered samples was obtained with increasing ZrO2 content. The observed improvement in the properties of the sintered composites was attributed to the presence of the hard dispersoids of ZrO2 and formation of solid solution strengthening and hard Cr3Ni2 phases within the matrix of the sintered composites.
“…The decrease in H n with P max is referred to as the indentation size effect (ISE) and has been observed even in other metallic glasses, such as MSR and BMGs (Steenberge et al, 2007;Li et al, 2008;Li et al, 2009a;Huang et al, 2010;Jang et al, 2011;Xu et al, 2014;Xue et al, 2016). In the case of crystalline materials, the ISE is attributed to the presence of geometrically necessary dislocations (due to high plastic strain gradients) at low p (Nix and Gao, 1998;Pharr et al, 2010;Prasad and Ramesh., 2019;Kathavate et al, 2021). However, owing to the amorphous nature, the ISE in metallic glasses cannot be explained by the dislocation theory and is often attributed to the shear band nucleation and propagation characteristics underneath the indentation (Li et al, 2009b) and evolution of free volume during indentation (Yang and Nieh, 2007b).…”
Section: Variation Of Nanohardness With the Indentation Loadmentioning
In this work, the deformation behavior of as-prepared (AP) and structurally relaxed (SR) Cu–Zr–based nanoglasses (NGs) are investigated using nano- and micro-indentation. The NGs are subjected to structural relaxation by annealing them close to the glass transition temperature without altering their amorphous nature. The indentation load, p, vs. displacement, h, curves of SR samples are characterized by discrete displacement bursts, while the AP samples do not show any of them, suggesting that annealing has caused a local change in the amorphous structure. In both the samples, hardness (at nano- and micro-indentation) decreases with increasing p, demonstrating the indentation size effect. The micro-indentation imprints of SR NGs show evidence of shear bands at the periphery, indicating a heterogeneous plastic flow, while AP NG does not display any shear bands. Interestingly, the shear band density decreases with p, highlighting the fact that plastic strain is accommodated entirely by the shear bands in the subsurface deformation zone. The results are explained by the differences in the amorphous structure of the two NGs.
“…A large number of studies have been devoted to solving the problem of ISE in various materials based on different theory methods so far, such as the Nix-Gao model, Hays-Kendall model, elastic recovery model, energy balance approach, and proportional specimen resistance model. [12,13] Of all these models, the true hardness value (i.e., a depth-independent hardness) was obtained by different research to describe the ISE of various materials. The relationship between the true hardness value and the macroscopic constitutive law is not established, and the focus is more on discussing the nanomechanical properties.…”
Section: Introductionmentioning
confidence: 99%
“…[15,16] The extent of ISE usually depends on the intrinsic length scales of the material, which is attributed to the plastic strain gradient, [17] elastic recovery, work-hardening mechanisms, and high dislocation nucleation stresses underneath indentation. [13] Nix-Gao described the size effect of indentation hardness by using geometrically necessary dislocations (GNDs) and the intrinsic microstructural length scales. [12] However, the bulk of the research shows that there are great differences between the theoretical prediction and experimental results for the…”
Indentation size effect (ISE) is a critical feature for investigating the local properties of materials using the indentation test method. Although there are numerous works on the indentation response, there is a lack of data in the literature on the association between nanoindentation and uniaxial compression. Herein this study, uniaxial compression tests combined with Digital Image Correlation Technique are conducted on Ti6Al4V alloy with a focus on investigating the elastic–plastic properties and obtaining the accurately constitutive relation. Then, an ISE model of Ti6Al4V is established based on this constitutive relation and strain gradient theory. Indentation hardness, predicted by this proposed model, agrees well with the measurement by nanoindentation experimental techniques. This model can be used to bridge the gap between the uniaxial stress–strain and the depth‐dependent hardness, and clarifies the effect of the strain hardening on indentation hardness. The significance of this model is that it provides a direct and reasonable theory foundation to investigate ISE by uniaxial compression, and promotes the potential application of nanoindentation.
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