The High Temperature Deformation Behavior of TiC0.98 Grown by the Floating Zone Technique

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In order to clarify the effect of C/Ti atom ratios(χ) on the deformation behavior of TiC χ at high temperature, single crystals having a wide range of χ, from 0.56 to 0.96, were deformed by compression test in a temperature range of 1183~2273 K and in a strain rate range of 1.9 × 10 −4~5.9 × 10 −3 s −1. Before testing, TiC χ single crystals were grown by the FZ method in a He atmosphere of 0.3 MPa. The concentrations of combined carbon were determined by chemical analysis and the lattice parameters by the X-ray powder diffraction technique. It was found that the high temperature deformation behavior observed is the χ-less dependent type, including the work softening phenomenon, the critical resolved shear stress, the transition temperature where the deformation mechanism changes, the stress exponent of strain rate and activation energy for deformation. The shape of stress-strain curves of TiC 0.96 , TiC 0.85 and TiC 0.56 is seen to be less dependent on χ, the work hardening rate after the softening is slightly higher in TiC 0.96 than in TiC 0.85 and TiC 0.56 . As χ decreases the work softening becomes less evident and the transition temperature where the work softening disappears, shifts to a lower temperature. The τ c decreases monotonously with decreasing χ in a range of χ from 0.86 to 0.96. The transition temperature where the deformation mechanism changes shifts to a lower temperature as χ decreases. The activation energy for deformation in the low temperature region also decreased monotonously as χ decreased. The deformation in this temperature region is thought to be governed by the Peierls mechanism.

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confidence: 88%

Section: Methodsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…The details of the testing machine, heating method and temperature measurement used were the same as those described in previous papers. 12,13) 3. Results .…”

Section: Methodsmentioning

confidence: 99%

Section: )mentioning

confidence: 99%

See 3 more Smart Citations

Effect of C/Ti Atom Ratio on the Deformation Behavior of TiCχ Grown by FZ Method at High Temperature

Shin¹

2013

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Deformation Properties of TiC-Mo Eutectic Composite at High Temperature

Shin

2013

The deformation properties of a TiC-Mo eutectic composite were investigated in a compression test at temperatures ranging from room temperature to 2053 K and at strain rates ranging from 3.9 × 10 . It was found that this material shows excellent high-temperature strength as well as appreciable room-temperature toughness, suggesting that the material is a good candidate for high-temperature application as a structure material. At a low-temperature, high strength is observed. The deformation behavior is different among the three temperature ranges tested here, i.e., low, intermediate and high. At an intermediate temperature, no yield drop occurs, and from the beginning the work hardening level is high. At a high temperature, a yield drop occurs again, after which deformation proceeds with nearly constant stress. The temperature-and yield-stress-dependence of the strain is the strongest in this case among the three temperature ranges. The observed hightemperature deformation behavior suggests that the excellent high-temperature strength is due to the constraining of the deformation in the Mo phase by the thin TiC components, which is considerably stronger than bulk TiC. It is also concluded that the appreciable room-temperature toughness is ascribed to the frequent branching of crack paths as well as to the plastic deformation of the Mo phase.

Ductile-Brittle Transition Property of Sintered TiC-Nb Composites

신¹

2014

In order to clarify the effect of Nb addition on the ductile-brittle transition property of sintered TiC, TiC-10 mol% Nb composites were researched using a three-point bending test at temperatures from room temperature to 2020 K, and the fracture surface was observed by scanning electron microscopy. It was found that the Nb addition decreases the ductile-brittle transition temperature of sintered TiC by 300 K and increases the ductility. The room temperature bending strength was maintained at up to 1800 K, but drastically dropped at higher temperatures in pure TiC. The strength increased moderately to a value of 320 MPa at 1600 K in TiC-10 mol% Nb composites, which is 40 % of the room temperature strength. Pores were observed in both the grains and the grain boundaries. It can be seen that, as Nb was added, the size of the grain decreased. The ductile-brittle transition temperature in TiC-10 mol% Nb composites was determined to be 1550 K. Above 1970 K, yieldpoint behavior was observed. When the grain boundary and cleavage strengths exceed the yield strength, plastic deformation is observed at about the same stress level in bending as in compression. The effect of Nb addition is discussed from the viewpoint of ability for plastic deformation.