“…The failure stress increased up to 6 GPa when the strain rate increased to 2000/s, which implies strong strain-rate sensitivity of the material. A similar phenomenon had been reported elsewhere[9,19,28]. The 'plateau' regions of the stress-strain curves represent the reflected signals in the SHPB system after the sample was crushed, and may be caused by accumulation of plastic deformation and damage.…”
supporting
confidence: 79%
“…Two sets of specimens were cut, with a nominal dimension of 3×3×6 mm 3 and 6×6×4 mm 3 for quasi-static and dynamic (SHPB) compression tests, respectively. The size of the specimen was decided based on the work of [19] where similar dimension (2×2×3 mm 3 ) was used. The sample size was also verified against the capability of the testing machines.…”
Section: Experimental Details 21 Materials and Specimenmentioning
This paper compared the mechanical behavior of 6H SiC under quasi-static and dynamic compression. Rectangle specimens with a dimension of 3 × 3 × 6 mm3 were used for quasi-static compression tests under three different loading rates (i.e., 10−5/s, 10−4/s, and 10−3/s). Stress–strain response showed purely brittle behavior of the material which was further confirmed by scanning electron microscopy (SEM)/transmission electron microscopy (TEM) examinations of fractured fragments. For dynamic compression, split Hopkinson pressure bar (SHPB) tests were carried out for cubic specimens with a dimension of 6 × 6 × 4 mm3. Stress–strain curves confirmed the occurrence of plastic deformation under dynamic compression, and dislocations were identified from TEM studies of fractured pieces. Furthermore, JH2 model was used to simulate SHPB tests, with parameters calibrated against the experimental results. The model was subsequently used to predict strength and plasticity-related damage under various dynamic loading conditions. This study concluded that, under high loading rate, silicon carbide (SiC) can deform plastically as evidenced by the development of nonlinear stress–strain response and also the evolution of dislocations. These findings can be explored to control the brittle behavior of SiC and benefit end users in relevant industries.
“…The failure stress increased up to 6 GPa when the strain rate increased to 2000/s, which implies strong strain-rate sensitivity of the material. A similar phenomenon had been reported elsewhere[9,19,28]. The 'plateau' regions of the stress-strain curves represent the reflected signals in the SHPB system after the sample was crushed, and may be caused by accumulation of plastic deformation and damage.…”
supporting
confidence: 79%
“…Two sets of specimens were cut, with a nominal dimension of 3×3×6 mm 3 and 6×6×4 mm 3 for quasi-static and dynamic (SHPB) compression tests, respectively. The size of the specimen was decided based on the work of [19] where similar dimension (2×2×3 mm 3 ) was used. The sample size was also verified against the capability of the testing machines.…”
Section: Experimental Details 21 Materials and Specimenmentioning
This paper compared the mechanical behavior of 6H SiC under quasi-static and dynamic compression. Rectangle specimens with a dimension of 3 × 3 × 6 mm3 were used for quasi-static compression tests under three different loading rates (i.e., 10−5/s, 10−4/s, and 10−3/s). Stress–strain response showed purely brittle behavior of the material which was further confirmed by scanning electron microscopy (SEM)/transmission electron microscopy (TEM) examinations of fractured fragments. For dynamic compression, split Hopkinson pressure bar (SHPB) tests were carried out for cubic specimens with a dimension of 6 × 6 × 4 mm3. Stress–strain curves confirmed the occurrence of plastic deformation under dynamic compression, and dislocations were identified from TEM studies of fractured pieces. Furthermore, JH2 model was used to simulate SHPB tests, with parameters calibrated against the experimental results. The model was subsequently used to predict strength and plasticity-related damage under various dynamic loading conditions. This study concluded that, under high loading rate, silicon carbide (SiC) can deform plastically as evidenced by the development of nonlinear stress–strain response and also the evolution of dislocations. These findings can be explored to control the brittle behavior of SiC and benefit end users in relevant industries.
“…The clear grain boundary is presented for Fig. 3c and there is amorphous coat with about 5~10 nm thickness at the grain interface, which is considered to be one of the major causes of nitride ceramic with superplasticity 23,24 . The amorphous coat is usually formed by chemical reaction from (1) to (5) 9 .Figure 3Scanning electron microscopy and transmission electron microscopy images of Sialon-based ceramic compacts before deformation in an electric field.…”
The utralow-temperature superplastic forging for sialon-based nanocomposites is reported for the first time. Sialon-based nanocomposites, with an average grain size smaller than 50 nm and 98.5% relative density, were prepared with nano-sized row powders by the spark plasma sintering (SPS) technique at a record ultralow sintering temperature of 1150 °C. An excellent gear is forged at the ultralow deformation temperature of 1200 °C with nanosized grains without any cracking. The maximum strain rate achieved is over 10
−1
s
−1
, and a compression strain is more than 0.9. The practical application for superplastic forming of nitrogen ceramics is much more difficult than that for oxide ceramics because of the high deformation temperature and low strain rates. The present findings present a bright prospect for the near-net-shape superplastic forming of nitrogen ceramics.
“…In most oxide ceramics, the superplastic deformation always needs a lower strain rate of <10 −5 s −1 and a higher deformation temperature of >1450 °C. Obviously, for industrial applications, the superplastic formation needs a higher efficiency (higher strain rate) and a lower production cost (lower deformation temperature) [13]. This means that the superplasticity of oxide ceramics should be enhanced to accommodate the industrial demands.…”
In this study, the compressive deformation of zirconia toughened alumina (ZTA) ceramics doped with different amounts of TiO2 dopants were investigated in the temperature range of 1300–1400 °C to evaluate the stress exponent (n value) and apparent deformation activation energy (Q value). With 0–8 wt.% TiO2 dopants, the n values and Q values of the TiO2-doped ZTA ceramics were calculated as 2–3 and 605–749 kJ/mol, respectively. Moreover, three grain boundary features were observed in these deformed materials, named the clean grain boundary, thin liquid phase grain boundary, and thick liquid phase grain boundary. Based on the deformation behavior and microstructure evolution, it was found that the lower apparent activation energy and higher strain rate of TiO2-doped ZTA ceramics are intensively related to the grain boundary feature.
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