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Synthesis of Nano-Crystalline RuAl by Mechanical Alloying
( Anil Borah ),( P. S. Robi ),( A. Srinivasan ) 대한금속재료학회 ( 구 대한금속학회 ) 2007 METALS AND MATERIALS International Vol.13 No.4
Nano-crystalline RuAl was synthesised by mechanical alloying. The evolution of the nano-crystalline RuAl phase during the mechanical alloying process using ruthenium and aluminium powders was studied. During the milling process, the peaks corresponding to reflections from the aluminium planes disappeared. The variation of crystallite size and microstrain with milling time was evaluated using X-ray diffraction (XRD) patterns. Though the XRD results showed the formation of a RuAl phase after 7 h of milling, scanning electron microscopy studies revealed that the RuAl phase was formed after 2 h of milling. The analysis revealed that average crystallite sizes of 17 and 120 nm were obtained for RuAl and Ru phases, respectively, during the milling process. Density value of 97 % of the theoretical value was obtained for the milled powder mixture after cold compaction and sintering.
Calorimetric Study of Precipitation Kinetics of Al–Cu–Mg and Al–Cu–Mg–0.06 wt.% Sn Alloys
Sanjib Banerjee,P. S. Robi,A. Srinivasan 대한금속·재료학회 2010 METALS AND MATERIALS International Vol.16 No.4
Al–Cu–Mg alloy and Al–Cu–Mg alloy micro alloyed with 0.06 wt.% of Sn were prepared by casting route. Precipitation kinetics of these alloys was studied by differential scanning calorimeter (DSC) from 50 °C to 550 °C at constant heating rates of 10 °C/min, 15 °C/min, 20 °C/min and 25 °C/min. DSC curves of the Al–Cu–Mg alloy revealed two exothermic peaks in the temperature ranges from 245.3 °C to 257.5 °C and from 267.7 °C to 288.3 °C. For Al–Cu–Mg–0.06 wt.% Sn alloy, two similar exothermic peaks were observed in the temperature ranges from 233.5 °C to 252.1 °C and from 271.3 °C to 296.7 °C. Both peak temperatures increased with increase in heating rate. The reaction kinetics was investigated and the kinetic parameters of the rate equation were determined from the experimental results by using a new methodology. Activation energy of precipitation increased from 96.3 kJ/mole to 99.1 kJ/mole for the first exothermic peak and decreased from 78.0 kJ/mole to 69.0 kJ/mole for the second exothermic peak due to trace addition of 0.06 wt.% of Sn. Fairly good accuracy was obtained when the rate of reaction predicted using the derived parameters was compared with the experimental values.
Saptarshi Dutta,P. S. Robi 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.8
High-temperature tensile tests were carried out on Zr-2.5Nb alloy in the temperature range of 298-873 K for both longitudinal and transverse specimen directions. Kocks-Mecking (K-M) approach was used to analyze the tensile flow and work-hardening nature of this alloy. The graph of instantaneous work hardening rate (θ = dσ/dε, where true stress is denoted by σ and true plastic strain by ε) with stress exhibited two-stage strain hardening behavior at all temperatures. The graph of θ vs σ and the variation in the parameters of strain hardening displayed three temperature zones, with a plateau region in 473-573 K. A fairly good correlation was achieved between the strain hardening parameters measured with the K-M method and the Voce equation at the above-mentioned temperature range.
Saptarshi Dutta,P. S. Robi 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.12
In the present work, creep tests on Zr–2.5Nb alloy at different stresses and temperatures in the two-phase region were carriedout. The three creep regions were very distinct at low stresses and temperatures, whereas the secondary creep regionsnarrowed down considerably at higher temperatures and stresses. Data obtained from these creep tests were used to simulatethe creep curves by multiple linear regression (MLR) and artificial neural network (ANN) modeling. The MLR model wasable to predict the primary creep region accurately; however, it over-predicted the secondary creep region. ANN modelcould simulate all the three creep regions with very high accuracy, where 98% of the creep strain could be predicted withina deviation of ± 5%. Two different creep experiments were conducted to verify the predictability of the proposed models. The results indicate that the ANN technique can be used to predict the creep curves of two-phase alloys.