Showing 3 results for Arrhenius Relation
Seyed Mohammad Mirghasemi, Ehsan Mohammad Sharifi, Gholam Hossein Borhani,
Volume 21, Issue 0 (3-2024)
Abstract
The hot deformation behavior modeling and microstructural evolution of low-carbon boron steels with Ti (FBT) and Nb (FBN) additions were investigated and compared with a baseline boron-treated steel (FB) in our previous work. Hot compression tests were conducted at temperatures of 850–1150 °C and strain rates of 0.01–10 s⁻¹. Flow curve analysis revealed that both Ti and Nb increased flow stress and delayed the onset of dynamic recrystallization (DRX), with the effect more pronounced in FBN. Constitutive analysis based on the Arrhenius model showed that the activation energy of deformation increased from 293.37 kJ/mol in FB to 314.15 kJ/mol in FBT and 353.04 kJ/mol in FBN, highlighting the strong pinning effect of precipitates. Critical stresses and strains (σc, σp, εc, εp) followed the order FB < FBT < FBN, indicating higher resistance to recrystallization in the microalloyed steels. DRX kinetics, modeled using the Avrami equation, yielded exponents of 2.09, 1.65, and 1.88 for FB, FBT, and FBN, respectively, confirming that Ti suppressed nucleation more strongly than Nb. Microstructural analysis demonstrated that Ti inhibited BN formation and promoted TiN/Ti(C,N), whereas Nb retained BN and generated Nb(C,N), mainly at MnS interfaces. Grain size distribution analysis revealed that both FBT and FBN exhibited significantly finer and more homogeneous grains compared to FB, with average grain sizes at 1150 °C (0.1 s⁻¹) of 17.3 μm in FBT and 17.0 μm in FBN, nearly half that of FB (33.6 μm). Overall, Ti and Nb additions distinctly altered the high-temperature deformation and recrystallization mechanisms of boron steels, enhancing grain refinement while suppressing DRX, thereby extending the findings of our previous study on FB.
Seyed Mohammad Mirghasemi, Ehsan Mohammad Sahrifi, Gholam Hossein Borhani, Mirtaher Seyed Beigi,
Volume 21, Issue 4 (12-2024)
Abstract
In this study, the hot deformation and dynamic recrystallization behavior of low carbon steel containing 21 ppm boron was investigated. After homogenizing the samples at 1250 ℃ for 1-hour, hot compression tests were conducted at temperatures ranging from 850 ℃ to 1150 ℃ and strain rates from 0.01 to 10 s⁻¹, resulting in strain-stress flow curves. Following corrections, calculations and modeling were performed based on Arrhenius equations. Among them, the hyperbolic sine relationship provided the most accurate estimate and was selected as the valid model for the applied strain range. According to this model, the deformation activation energy (Q), was determined to be 293.37 KJ/mol. Additionally, critical and peak stress and strain values were obtained for each temperature and strain rate, and power relationships were established to describe their variation with respect to the Zener-Hollomon parameter (Z). Recrystallization fractions were derived by comparing the hypothetical recovery curves with the material flow curves, and the results were successfully modeled using the Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation. The Avrami exponent was measured at approximately 2, indicating that nucleation predominantly occurred at grain boundaries. Microstructural analysis revealed that at higher Z values, recrystallization occurred along with a fraction of elongated grains, while lower Z values resulted in a greater fraction of equiaxed dynamic recrystallization (DRX) grains. The average grain sizes after compression tests at 950 ℃, 1050 ℃, and 1150 ℃ were measured as 21.9 µm, 30.4 µm, and 33.6 µm respectively at a strain rate of 0.1 s⁻¹, and 17.7 µm, 28.7 µm, and 31.3 µm at 1 s⁻¹. The overall microstructure displayed a more uniform grain size distribution with increasing deformation temperature.
Krishna Jyothi N, Keerthi M., Gnana Kiran M., Venkata Kamesh Vinjamuri, Prakash Babu Kanakavalli, Krupakaran R.l, Nandini P.s.v., Rao M.c., D. Madhavi Latha, Mahamuda Sk.,
Volume 22, Issue 4 (12-2025)
Abstract
This research systematically examines the structural, electrical, and optical characteristics of Tamarind Seed Polysaccharide (TSP)--based biopolymer electrolytes that are doped with varying concentrations of sodium iodide (NaI). Composite films were synthesized using the solution cast technique in weight percent ratios of TSP: NaI (100:0, 90:10, 80:20, 70:30) and subsequently characterized employing X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), UV–Vis spectroscopy, and impedance analysis. The XRD analysis indicated that the 80:20 composition displayed the highest degree of amorphousness, which is associated with improved ionic conductivity and reduced crystallite size. The FTIR analysis corroborated the occurrence of complexation between TSP and NaI, while the temperature-dependent conductivity measurements conformed to Arrhenius behaviour, with the 80:20 film achieving the ionic conductivity (1.97x10⁻4 S/cm) and the lowest activation energy (0.69 eV). Optical absorption investigations revealed a decrease in the bandgap from 3.92 (pure TSP) to 2.68 eV (80:20 film). Minimum optical energy bandgaps were achieved for the optimized film. Opto-dielectric investigations further demonstrated that the 80:20 formulation exhibited optimal dielectric permittivity and loss. The results underscore the potential applicability of TSP–NaI biopolymer systems as sustainable, high-performance polymer electrolytes.
