• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1995년도 추계학술대회논문집
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• pp.172-180
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• 1995

Isothermal interrupted deformation behavior of 10vol.%SICp/AI-Si composites was investigated by hot torsion test at the temperature ranges from 27$0^{\circ}C$ to 43$0^{\circ}C$ and at strain rate range of 1.26X10-2~2.16X10-1/sec. With increasing pass strain, flow stresses were high compared to continuous deformation condition. Fractional softening was increased with temperature imterruption time and pass strain. Fractional softening of 10vol.%SiCp/AI-Si composites was lower than that of AI-Si matrix at 37$0^{\circ}C$. However at high temperature of 43$0^{\circ}C$, SiC particle promoted static softening, diminishing the dislocation density at the interface of AI-Si matrix and reinforcements, then this resulted in higher fractional softening in composites. Both of failure strain improved reducing the fracture of SiC particle and Si precipitates above 32$0^{\circ}C$, however at low temperature of 27$0^{\circ}C$, the softening effect by interrupted deformation was found to be negligible.

• 소성∙가공
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• 제4권2호
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• pp.169-179
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• 1995

Static restoration mechanism during hot interrupted deformation of Cu-Zn alloy was studied in the temperature range from $550^{\circ}C$ to $750^{\circ}C$ and at a constant strain rate of 0.1/sec. At a given temperature, the hot interrupted deformations were performed with variation of interrupted time $t_i$ form 1 to 50 sec and of interrupted strain ${\varepsilon}_i$ from 0.15 to 0.90. From the analysis of the values of the critical strain of ${\varepsilon}_c$ for tje initiation of dynamic recrystallization and the peak strain of${\varepsilon}_p$, the relationship ${\varepsilon}_c{\fallingdotseq}0.7{\varepsilon}_p$ was obtained. It was clarified that the softening of the interrupted deformation was mainly the static recrystallization and the fractional softening(FS) which was over 30% mostly confirmed this result. The fractional softening of the interrupted time $t_i$ especially and pre-strain. The FS increased with increasing strain rate, interrupted time and pre-strain. The change of microstructures after hot deformation could be predicted by the FS. when the FS was 30~100%, static recrystallization was happened and grain growth was observed at the condition which was $750^{\circ}C$ deformation temperature, 0.45 prestrain and this condition's FS value was over 100%.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.77-80
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• 1997

The torsion tests in the range of 900~110$0^{\circ}C$, 5.0$\times$10-2~5.0$\times$100/sec were performed to study the recry stallization behavior of 304 stainless steel in the high temperature multistage deformation. The no-recrystallization temperature(Tnr) and fractional softening(FS) were determined by the change of flow curves. The inflection points of stress slope were moved to lower temperature area as the strain rate and the interrupt time were increased. From the multipass flow curve, the intersection between pass stress and FS curve was corresponding to the pass which the FS dropped abruptly and it was shown that the recrystallization area could be determined by the FS measurement in multipass deformation.

• 소성∙가공
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• 제10권1호
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• pp.42-52
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• 2001

The static softening mechanisms of 304 stainless steel were studied by hot torsion test. The interrupted deformation tests were performed In the range of 900~$1100^{\circ}C$ and 5.0$\times$$10^{-2}$- 5.0$\times$$10^0$/sec. The metadynamic recrystallization (MDRX) could be distinguished from the static recrystallization (SRX). Comparison of the softening kinetics between MDRX and SRX showed that the rate of MDRX was more rapid than that of SRX for the same deformation variables. To the exact prediction of MDRX, the MDRX parameter, which could be simultaneously estimated by the interpass time and Zener-Hollomon parameter, was developed. The time lot 50% MDRX, $t_{0.5} was modeled using the deformation parameters : $t_{0.5} = 1.33\times10^{-11}$ $\.\varepsilon^{-0.41}$ D exp(230.3kJ/mol/RT) and the predicted value was very correspondent with the measurement. It was found that the static parameters such as interpass time can control the dynamic states in the several successive deformation process.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 추계학술대회논문집
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• pp.185-188
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• 1997

Static restoration during hot interrupted deformation of 304 stainless steel was studied in the temperature range from 900 to 1100$^{\circ}C$ under various strain rate of 0.05∼ 5/sec and pass strain of 1/4∼3 times peak strain. The static restoration was dependent on the pass strain, deformation temperature and strain rate. Fractional softening(FS) values increased with increasing strain rate, deformation temperature and pass strain. Recystallization kinetics was well explained by the Avrami equation and the time for 50% recrystallization was evaluated using equation of t0.5=2.01${\times}$10-10$\varepsilon$-.156$\varepsilon$ -0.81Dexp(196.66/RT)