“…The DRX grain sizes are almost equal at the same of deformation condition in spite of different pre-existing grain sizes. This result is in good agreement with conclusion reported previously [7] . …”
Section: Effect Of Deformation Temperaturesupporting
The dynamic recrystallization (DRX) behaviors in SPHC steel were investigated with hot compression tests at deformation temperatures of 950-1 150 ℃, strain rates of 0.1-15 s −1 , and initial austenite grain sizes of 86-232 µm. The effects of deformation temperature, strain, strain rate and the initial austenite grain size on the microstructural evolution during DRX were studied in detail. The results show that DRX is observed under the condition of the Zener-Hollomon parameter being less than 1.07×10 13 s −1 . The deformation activation energy for SPHC steel is calculated to be 299.4 kJ/mol by regression analysis. Austenite grain size of DRX is refined with decreasing temperature and increasing strain rate under steady state conditions, but it is not influenced by the initial grain size. The mathematical equation of DRX grain size of SPHC steel is obtained.
“…The DRX grain sizes are almost equal at the same of deformation condition in spite of different pre-existing grain sizes. This result is in good agreement with conclusion reported previously [7] . …”
Section: Effect Of Deformation Temperaturesupporting
The dynamic recrystallization (DRX) behaviors in SPHC steel were investigated with hot compression tests at deformation temperatures of 950-1 150 ℃, strain rates of 0.1-15 s −1 , and initial austenite grain sizes of 86-232 µm. The effects of deformation temperature, strain, strain rate and the initial austenite grain size on the microstructural evolution during DRX were studied in detail. The results show that DRX is observed under the condition of the Zener-Hollomon parameter being less than 1.07×10 13 s −1 . The deformation activation energy for SPHC steel is calculated to be 299.4 kJ/mol by regression analysis. Austenite grain size of DRX is refined with decreasing temperature and increasing strain rate under steady state conditions, but it is not influenced by the initial grain size. The mathematical equation of DRX grain size of SPHC steel is obtained.
“…In their study, the effects of deformation temperature and strain rate on the DRX kinetics were considered. However, a large amount of work [26][27][28][29] showed that the characteristics of DRX behavior depend on not only the deformation temperature and strain rate but also the initial grain size for the metals or alloys. Thus, the DRX kinetics in the hot deformed 42CrMo steel still need further investigation by considering the effects of initial grain size on the DRX behavior.…”
“…Figure 4 indicates the variation of flow stress with reciprocal temperature. According to Equation (8), the value of Q can be derived from the average slope of linearly regressed data, which is 487.21 kJ mol −1 , higher than Mn–Cr gear steel (378.60 kJ mol −1 ) [21], Q235(363.10 kJ mol −1 ) steel [22] and 316LN stainless steel (458.85 kJ mol −1 ) [12]. Figure 4 Relationship between ln(sinh(ασ p )) and 1/ T. Figure 5 Relationship between flow stress and Zener–Hollomon parameter.…”
High strain isothermal compression tests at temperatures of 700–1200°C and strain rates of 0.1–50 s−1 were performed in a Gleeble-3800 thermal simulator to investigate the hot deformation behaviour of a high-alloy Cr–Co–Mo–Ni gear steel, and the constitution equation and hot processing map were established based on these experiments. The results show that the flow stress can be described by the constitutive equation in hyperbolic sine function, and the optimum hot working regions are at the temperature of 1000–1100°C and strain rate of 0.3–1.0 s−1. Optical microscopy observations of austenite grains indicate that dynamic recrystallisation occurs when the deformation temperature is over 900°C. The forging was successfully produced on the basis of the above-described researches.
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