Low-Temperature Processing of ZrB2-ZrC Composites by Reactive Hot Pressing

Rangaraj, Lingappa; Suresha, S. J.; Divakar, C; Jayaram, Vikram

doi:10.1007/s11661-008-9500-y

Cited by 59 publications

(65 citation statements)

References 35 publications

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“…To account for that we have modified the model of Helle et al [25][26][27] Constitutive equations are shown in Eq. (2)(3)(4)(5).…”

Section: (4) Densification Mechanism In Rhp Of Zrc Xmentioning

confidence: 99%

“…4 Reactive hot pressing (RHP), on the other hand, showed more promise and recent work on RHP of zirconium (Zr) -boron carbide (B 4 C) and Zr: carbon (C) powder mixture yielded full density at much lower temperatures. [5][6][7] Stoichiometric 3Zr:B 4 C composition required 1600°C and 40 MPa to achieve 96% relative density (RD), whereas nonstoichiometric 3.5Zr:B 4 C composition yielded 98% RD at a significantly lower temperature of 1200°C. 5 The study on RHP has been extended to different molar ratios of Zr:C and it was observed that the nonstoichiometric composition always displayed a better densification than the stoichiometric composition.…”

Section: Introductionmentioning

confidence: 99%

“…[5][6][7] Stoichiometric 3Zr:B 4 C composition required 1600°C and 40 MPa to achieve 96% relative density (RD), whereas nonstoichiometric 3.5Zr:B 4 C composition yielded 98% RD at a significantly lower temperature of 1200°C. 5 The study on RHP has been extended to different molar ratios of Zr:C and it was observed that the nonstoichiometric composition always displayed a better densification than the stoichiometric composition. 6,7 The stoichiometry of ZrC in equilibrium with the Zr-rich solid solution varies from 37.8 mol% C (ZrC 0.6 ) at 500°C to 33.3 mol% C (ZrC 0.5 ) at 1805°C while the maximum C content is 50 mol% (ZrC) in equilibrium with C. 8 The densification observed in Zr-C and Zr-B 4 C powder mixture during RHP, is mostly attributed to the nonstoichiometry of ZrC and to the fine grain size of reaction products.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Zirconium on the Densification of Reactively Hot‐Pressed Zirconium Carbide

2014

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Densification mechanisms involved during reactive hot pressing (RHP) of zirconium carbide (ZrC) have been studied. RHP has been carried out using zirconium (Zr) and graphite (C) powders in the molar ratios 1:0.5, 1:0.67, 1:0.8, and 1:1 at 40 MPa, 800°C-1200°C for different durations. The volume fractions of phases formed, including porosity, are determined from the measured density and from Rietveld analysis. Increased densification with an increasing nonstoichiometry in carbon has been observed. Microstructural and X-ray diffraction observations coupled with the predictions of a model based on the constitutive laws governing plastic flow of zirconium suggest that the better densification of nonstoichiometric compositions arise from the higher amount of starting Zr and also the longer duration of its availability for plastic flow during RHP. Volume shrinkage due to reaction between Zr and C and the gradual elimination of the soft metal phase limit the final density achievable. Based on these observations, a twostep RHP carried out at 800°C and 1200°C leads to a better densification than a single RHP at 1200°C.

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“…To account for that we have modified the model of Helle et al [25][26][27] Constitutive equations are shown in Eq. (2)(3)(4)(5).…”

Section: (4) Densification Mechanism In Rhp Of Zrc Xmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of Zirconium on the Densification of Reactively Hot‐Pressed Zirconium Carbide

2014

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“…3. The calculated values of increments of the fracture toughness KIC for the composite materials ZrB 2 -SiC, ZrB 2 -ZrC, ZrB 2 -TiB 2 when the volume concentration of inclusions are of 10 -20 % [1,4,13,19,20].…”

Section: Resultsmentioning

confidence: 99%

Predicting the mechanical properties of ultra-high temperature ceramics

Skripnyak¹,

Skripnyak²

2017

LoM

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A model for predicting mechanical properties of ultra-high temperature ceramics (UHTC) and composites within a wide temperature range is presented. The model can be useful for predicting the mechanical properties of UHTC composites under dynamic loading and thermal shock. Results of calculations taking into account the dependences of the nonlinearity of normalized elastic moduli on the homologous temperature in the range T / T m = 0.2 -0.62 are presented.. Residual stresses in ZrB 2 composites reinforced with particles of refractory borides, carbides and nitrides after selective laser sintering (SLS) or spark plasma sintering (SPS) are predicted. It is shown that the fracture toughness K IC of UHTC increases at the sintering temperature in the range (0.45 -0.62) T m . The residual stress in the matrix of ceramic composites can be either negative or positive due to a difference between the thermal expansion coefficients of the matrix and inclusion phases. It is shown that the fracture toughness and the flexural strength of ZrB 2 matrix composites can be increased by 25 % by the introduction of inclusions of specially selected refractory strengthening phases. Dependence of the normalized strength of composites ZrB 2 -B 4 C on the logarithm of normalized strain rate can be described by a power law in the range of strain rates from 10 -3 to 10 6 s -1 and temperatures from 295 K to about 1673 K. Results of simulations confirm that the technologies of SLS and SPS can be used for the production of UHTC composites with high values of the specific strength and the fracture toughness.

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“…The material sintered at 1873 K (1600°C) displayed mechanical properties comparable to those previously reported for materials that had experienced higher sintering temperatures. Rangaraj et al [75,76] found that nonstoichiometric ZrC x played a crucial role in RHP of Zr-B 4 C powder mixtures at 1473 K (1200°C) and in ZrB 2 -SiC composites produced at 1873 K (1600°C).…”

Section: Reactive Hot Pressingmentioning

confidence: 99%