Influence of Niobium on the Beginning of the Plastic Flow of Material during Cold Deformation

Stoja Rešković,Ivan Jandrlić

doi:10.1155/2013/723725

Abstract

Investigations were conducted on low-carbon steel and the steel with same chemical composition with addition of microalloying element niobium. While tensile testing was carried out, the thermographic measurement was tacking place simultaneously. A specific behavior of niobium microalloyed steel was noticed. Test results have shown that, in the elastic deformation region, thermoelastic effect occurs, which is more pronounced in niobium microalloyed steel. Start of plastic flow in steel which is not microalloyed with niobium begins later in comparison to the microalloyed steel, and it is conducted so that, at the point of maximum stress, deformation zone is formed within which stresses grow. In steel microalloyed with niobium after proportionality limit, comes the occurrence of the localized increase in temperature and the occurrence of Lüders band, which propagate along the sample forming a deformation zone.

Highlights

Niobium microalloyed steel is low carbon steel with the addition of niobium up to 0.06%
In steel microalloyed with niobium after proportionality limit, comes the occurrence of the localized increase in temperature and the occurrence of Luders band, which propagate along the sample forming a deformation zone
The purpose of this paper is to investigate the beginning of plastic flow of niobium microalloyed steel during static tensile testing

Summary

Introduction

Niobium microalloyed steel is low carbon steel with the addition of niobium up to 0.06%. Accumulation of dislocations around the series of precipitates in the deformed grain creates the subboundaries and by process of recrystallization, the reduction of grain size is achieved [2] In this way, a fine grained structure and significantly improved properties are achieved compared to the same low-carbon steel without the addition microalloying element niobium. During the static tensile testing in some steels, comes the occurrence of localized plastic deformation after reaching the yield point. This phenomenon is the explained by rheological behavior of materials during the cold deformation. Niobium microalloyed steel has a clearly defined upper and lower yield point, and at certain conditions, shows a rheological behavior at the beginning of plastic deformation

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Conclusion