Effect of electric current pulses on the microstructure and niobium carbide precipitates in a ferritic-pearlitic steel at an elevated temperature

• Published in: Journal of materials research Vol. 30; no. 20; pp. 3049 - 3055
• Main Authors: Rahnama, Alireza, Qin, R.S.
• Format: Journal Article
• Language: English
• Published: New York, USA Cambridge University Press 28.10.2015; Springer International Publishing; Springer Nature B.V
• Subjects: Alloying elements; Alloys; Analysis; Applied and Technical Physics; Biomaterials; Current pulses; Electric current; Electric currents; Electronics; Elongation; Energy; Ferritic stainless steels; Grain size; High temperature; Inorganic Chemistry; Materials Engineering; Materials research; Materials Science; Mechanical properties; Microstructure; Nanotechnology; Niobium carbide; Nucleation; Pearlite; Precipitates; Precipitation; Scanning electron microscopy; Steel; Steels; Studies; Tensile stress; United Kingdom > UK; electromigration; steel; phase transformation
• ISSN: 0884-2914; 2044-5326
• DOI: 10.1557/jmr.2015.268

Niobium is an important alloying element in steels. In the present work an effort has been made to investigate the effect of electropulsing on the niobium carbide (NbC) at an elevated temperature (800 °C). The results show that the electropulsing treatment can generate an evenly distributed NbC by decreasing the kinetics barriers for precipitation. It has been also found that a semitransformed pearlite structure forms in such a way that the grains are oriented toward a direction parallel to that of the electric current flow. Furthermore, the electropulsed sample benefits from refined grain size. This is thought to be due to the electropulse-enhanced nucleation rate. Tensile testing has been carried out to compare the properties of electropulsed sample with that of without electropulsing. The results show that the sample with treatment has greater yield strength and ultimate tensile stress while its elongation is only 1% less that of the unelectropulsed samples. The improved mechanical properties of the sample with pulsing are attributed to its finer grain sizes as well as the elimination of precipitation free zones caused by the electropulsing treatment.