A Differential Scanning Calorimetry (DSC) Study of Phase Changes in an As-Received Zr-2.5Nb Pressure Tube Material during Continuous Heating and Cooling

2012 ◽  
Vol 706-709 ◽  
pp. 853-858 ◽  
Author(s):  
R.W.L. Fong ◽  
H. Saari ◽  
R. Miller ◽  
J. Teutsch ◽  
Sven C. Vogel
Keyword(s):  
Differential Scanning Calorimetry ◽  
Neutron Diffraction ◽  
Volume Fraction ◽  
Phase Changes ◽  
Pressure Tube ◽  
Continuous Heating ◽  
Tube Material ◽  
Scanning Calorimetry ◽  
Heating And Cooling ◽  
Β Phase

Differential scanning calorimetry (DSC) has been used to study the phase changes in samples of as-received Zr-2.5Nb pressure tube material by continuous heating and cooling. Two different heating rates (5 and 20°C/min) were used to heat the sample up to 1050°C. After a short time hold at 1050°C, all the samples were continuously cooled to 300°C at a rate of 20°C/min. On continuous heating, the DSC signals obtained showed two endothermic transitions. The low-temperature transition, occurring between about 500 and 650°C, is attributed to a thermal decomposition of metastable niobium-stabilized β-phase. The highertemperature transition, occurring between 600 and 950°C, is due to phase transformations of hcp α-Zr to bcc β-Zr, as previously confirmed in a companion study on the same pressure-tube material that was examined in-situ by neutron diffraction. The neutron diffraction results provided a positive identification of the two phases and also a quantification of the β-phase present in the sample at different heating temperatures, and thus provided a guide to extract the volume fraction of β-phase from the DSC signals obtained in this study. The DSC signals revealed only one exothermic transition which is correlated to the reverse transformation of β-Zr to α-Zr, as previously identified in the companion neutron diffraction study of the same pressure tube material.

scholarly journals Effect of β Phase Decomposition on Recrystallization in α-Zr Region in Zr-2.5%Nb Pressure Tube Material

2020 ◽  
Vol 58 (10) ◽  
pp. 672-679
Author(s):  
SungSoo Kim ◽  
Sang Yup Lim ◽  
Gyeong-Geun Lee
Keyword(s):  
Isothermal Annealing ◽  
Volume Fraction ◽  
Inverse Pole Figure ◽  
Pressure Tube ◽  
Stable Region ◽  
Phase Decomposition ◽  
Tube Material ◽  
Lattice Contraction ◽  
Β Phase ◽  
Annealing Study

The effects of β phase decomposition on recrystallization and texture variation in Zr-2.5% Nb alloy pressure tube material were investigated. Isothermal annealing was conducted at 350 to 550 <sup>o</sup>C for 240 hours, and isothermal annealing was performed at 500 <sup>o</sup>C for 240 to 3,000 hours. The recrystallization and texture variation were analyzed by inverse pole figure variation using the XRD and EBSD methods. Annealing in α-Zr region at below 610 <sup>o</sup>C induced recrystallization and texture variation in the α-Zr. These results differ from those from a previous annealing study of the α+β region at 750-830 <sup>o</sup>C. Annealing above 400 <sup>o</sup>C for 240 hours caused β-Zr decomposition into β-Nb. The decomposition of the β-phase by annealing above 475 <sup>o</sup>C caused a contraction of 7.5% in the d(110) spacing in the β-phase, and a reduction in the volume fraction of the β phase by about 80%. It seems that the stress internally formed by the lattice contraction of the β-phase provides the driving force for recrystallization. In addition, it suggests that the newly formed α-Zr produced by β phase decomposition provides new nucleation sites for recrystallization and causes texture variation in the α-Zr. The reason why the recrystallization and the texture variation occurs only in the α-Zr stable region at below 610 <sup>o</sup>C is discussed.

Microstructure investigation of rapidly solidified Al–V–Fe alloys

2002 ◽  
Vol 17 (4) ◽  
pp. 814-820 ◽  
Author(s):  
G. He ◽  
C. H. Shek ◽  
Joseph K. L. Lai ◽  
Z. Bian ◽  
X. D. Hui ◽  
...  
Keyword(s):  
Grain Size ◽  
Volume Fraction ◽  
Glass Forming Ability ◽  
Continuous Heating ◽  
Minor Effect ◽  
Scanning Calorimetry ◽  
Glass Forming ◽  
Heating And Cooling ◽  
Average Grain Size ◽  
Fe Alloys

The microstructures and their thermal behaviors of quenched Al94V4Fe2, Al90V8Fe2, Al86V8Fe6, and Al85V9Fe2Ni4 alloys were investigated by x-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. The as-quenched microstructures of the four alloys consist of quasicrystal particles and a fcc-α–Al matrix. The as-quenched Al86V8Fe6 and Al85V9Fe2Ni4 alloys also contain a small volume fraction of amorphous phase. All phases observed have fine morphologies with grain sizes of less than 100 nm. With the increase in V from 4 to 8 at.% at 2 at.% Fe, the average grain size decreases from 100 to 70 nm and the melting temperature of α–Al solid solution increases from 640 to 653 °C. The alloy with 8 at.% V has a finer and more stable microstructure than that of the alloy with 4 at.% V. The Fe addition has minor effect on grain size but improves the glass-forming ability. The Ni addition significantly improves the glass-forming ability and refines the microstructure. The metastable amorphous and quasicrystalline phases transform into a stable crystalline phase during continuous heating and cooling. The stable phases in these Al–V–Fe alloys include α–Al(V, Fe), Al10V, and Al80V12.5Fe7.5.

scholarly journals A STUDY OF PARAMETERS RELATED TO ANALYSIS OF TRANSITION TEMPERATURES AND ENTHALPIES OF POLYPROPYLENE BY DIFFERENTIAL SCANNING CALORIMETRY (DSC)

2002 ◽  
Vol 10 (11) ◽  
pp. 73-78
Author(s):  
Carlos R. Wolf ◽  
Emir Grave
Keyword(s):  
Differential Scanning Calorimetry ◽  
Material Characterization ◽  
Transition Temperatures ◽  
Nitrogen Flow ◽  
Thermoplastic Polymer ◽  
Scanning Calorimetry ◽  
Know How ◽  
Heating And Cooling ◽  
Polypropylene Material ◽  
Dsc Method

Polypropylene is a thermoplastic polymer, widely employed by converter industries to produce different plastic objects. In order to control and optimize the final properties of the polypropylene material, the evaluation of transition temperatures and enthalpies by Differential Scanning Calorimetry (DSC) has a very important role. Therefore, it is fundamental to know how the analytical conditions influence the results. In this study heating and cooling rates, 10°C/min and 20°C/min, and two different rates of nitrogen flow, 20mL/min and 50mL/min were investigated. It was concluded that thermal properties are influenced by rates of heating and rates of nitrogen flow. The best precision was obtained with the low heating rate, 10°C/min, and high flow rate, 50mL/min. These conditions are being used with the DSC method for polyolefin quality control and material characterization.

Analytical Models for the Systematic Errors of Differential Scanning Calorimetry Instruments

Volume 1 ◽  
2004 ◽  
Author(s):  
Adrian S. Sabau ◽  
Wallace D. Porter
Keyword(s):  
Differential Scanning Calorimetry ◽  
Phase Change ◽  
Computational Analysis ◽  
Systematic Errors ◽  
Analytical Models ◽  
Transition Temperatures ◽  
Scanning Calorimetry ◽  
Heating And Cooling ◽  
Dsc Measurements ◽  
Phase Transition Temperatures

Differential Scanning Calorimetry (DSC) measurements are routinely used to determine enthalpies of phase change, phase transition temperatures, glass transition temperatures, and heat capacities. In order to obtain data on the amount of phases during phase change, time-temperature lags, which are inherent to the measurement process, must be estimated through a computational analysis. An analytical model is proposed for the systematic error of the instrument. Numerical simulation results are compared against experimental data obtained at different heating and cooling rates.

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