The Effect of Niobium on the Microstructure and Phase Transformation Kinetics in Low-Carbon Medium Manganese Steels*

2015 ◽  
Vol 70 (6) ◽  
pp. 267-275 ◽  
Author(s):  
P. Peissl ◽  
R. Schneider ◽  
M. Rahofer ◽  
L. Samek ◽  
E. Arenholz
Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5443
Author(s):  
Mateusz Morawiec ◽  
Adam Skowronek ◽  
Mariusz Król ◽  
Adam Grajcar

This paper aims to analyze the effect of deformation on the phase transformation kinetics of low-carbon structural steel. The steel used for the investigation was subjected to two different dilatometric analyses using a DIL 805A/D device. The first analysis was to determine the phase transformation kinetics without deformation of austenite before cooling. Then, the analysis under deformation conditions was conducted to investigate the deformation effect on the transformation kinetics. Microscopic studies by light microscopy were performed. The essential part of the research was hardness analysis for different cooling rates and the creation of continuous-cooling-transformation (CCT) and deformation continuous-cooling-transformation (DCCT) diagrams. It was found that the deformation of the samples before cooling increases a diffusion rate in the austenite resulting in the corresponding increase of ferritic, pearlitic, and bainitic start temperatures, as well as shifting the austenite transformation product regions to a longer time. The increase of the transformation area and a decrease in grain size are observed for the deformed samples.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
A. R. Massih ◽  
Lars O. Jernkvist

AbstractWe present a kinetic model for solid state phase transformation ($$\alpha \rightleftharpoons \beta$$ α ⇌ β ) of common zirconium alloys used as fuel cladding material in light water reactors. The model computes the relative amounts of $$\beta$$ β or $$\alpha$$ α phase fraction as a function of time or temperature in the alloys. The model accounts for the influence of excess oxygen (due to oxidation) and hydrogen concentration (due to hydrogen pickup) on phase transformation kinetics. Two variants of the model denoted by A and B are presented. Model A is suitable for simulation of laboratory experiments in which the heating/cooling rate is constant and is prescribed. Model B is more generic. We compare the results of our model computations, for both A and B variants, with accessible experimental data reported in the literature covering heating/cooling rates of up to 100 K/s. The results of our comparison are satisfactory, especially for model A. Our model B is intended for implementation in fuel rod behavior computer programs, applicable to a reactor accident situation, in which the Zr-based fuel cladding may go through $$\alpha \rightleftharpoons \beta$$ α ⇌ β phase transformation.


Author(s):  
Nathan Fernandes Ignácio ◽  
Maisa Silva Fernandes ◽  
Diego Magalhães Baía ◽  
Ana Gabriela Conceição dos Santos ◽  
Felipe da Silva Siqueira ◽  
...  

2018 ◽  
Vol 67 (7) ◽  
pp. 070204
Author(s):  
Chong Tao ◽  
Wang Gui-Ji ◽  
Tan Fu-Li ◽  
Zhao Jian-Heng ◽  
Tang Zhi-Ping

2017 ◽  
Vol 371 ◽  
pp. 160-165
Author(s):  
Vladimir Burlaka ◽  
Kai Nörthemann ◽  
Astrid Pundt

It was recently shown that phases forming in thin films undergo a coherency state change depending on the film thickness. For Nb-H thin films, the coherency state was reported to change at about 38 nm. In this study the impact of the coherency state on the phase transformation kinetics is investigated for Nb films of two different film thicknesses (25 nm and 80 nm), below and above the state change thickness. The phase transformation in thin metal-hydrogen films can be studied by surface topography analyses via scanning tunneling microscopy (STM) because of the strong local lattice expansion of the hydride precipitates. STM on Nb-H reveals fast phase transformation kinetics for the 25 nm Nb-film, and much slower kinetics for the 80 nm film. This is suggested to be related to the change in the coherency between the Nb-matrix and the hydride precipitates.


2014 ◽  
Vol 50 (3) ◽  
pp. 1412-1426 ◽  
Author(s):  
Pere Barriobero-Vila ◽  
Guillermo Requena ◽  
Fernando Warchomicka ◽  
Andreas Stark ◽  
Norbert Schell ◽  
...  

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