Characterization of the peritectic reaction in medium-alloy steel through microsegregation and heat-of-transformation studies |
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Authors: | Brij K Dhindaw Tomas Antonsson Hasse Fredriksson Jose Tinoco |
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Affiliation: | 1.the Department of Metallurgical and Materials Engineering,Indian Institute of Technology,Kharagpur,India;2.the Department of Metalcasting,Royal Institute of Technology (KTH),Stockholm,Sweden;3.Research and Development,Outokumpu Copper,V?ster?s,Sweden |
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Abstract: | In the present work, the phenomenon of the peritectic reaction was characterized in a medium-alloy steel. Several directional
solidifcation and thermal-analysis experiments were done to investigate the reaction process. Directional solidification experiments
carried out did not tend to show any direct evidence of a peritectic reaction. Microsegregation studies on the directionally
solidified samples and those solidified under isothermal conditions bring out some interesting features. It has been documented
that if the segregation ratio for Ni is higher than that for Cr, there is a correlation that the peritectic reaction had occurred
in that region. On the other hand, a higher Cr segregation ratio as compared to Ni showed the possibility that the liquid
had directly transformed to γ-austenite without undergoing a peritectic reaction. Measurement of energies of transformations and the analysis of their
values in different segments of the cooling-curve differential thermal analysis (DTA) experiments have helped in understanding
the peritectic reaction. It is revealed that the transformation is more like diffusionless transformation, where γ-austenite directly precipitates from δ-ferrite. Indeed, this proposition is also supported by the segregation patterns for Cr and Ni obtained in the solidified
samples of this steel during directional solidifcation and DTA experiments and also by calculations to show the presence of
enough lattice defects or vacancies to aid the aforementioned transformation. |
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