The Role of Phase Hardness Differential on the Non-uniform Elongation of a Ferrite-Martensite Dual Phase Steel

Soudip Basu, Balila Nagamani Jaya, Anirban Patra, Sarbari Ganguly, Monojit Dutta, Anton Hohenwarter, Indradev Samajdar

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This study involved a commercial hot-rolled dual-phase (DP) steel consisting of martensite (~10 pct) and ferrite phases. The harder lath martensite was located at the grain boundaries and triple junctions of the equiaxed ferrite grains. Tempering and high-pressure torsion (HPT) were used to alter the phase hardness differential ∆H (where ΔH=HMartensite−HFerrite) of the DP. The relationship between ∆H and non-uniform elongation, εNU, or post-necking ductility under tensile deformation, was then explored. Tempering softened predominantly the martensite, while HPT increased the ferrite hardness. Both led to a reduction in ∆H. A drop in ∆H in the tempered DP resulted in a steady increase and eventual saturation in εNU. On the other hand, a ∆H decrease in the HPT specimens showed an initial increase in εNU followed by a drop. Strain analysis, with optical digital image correlation during tensile deformation of the tempered DP samples, clearly related the formation of strain localization with ∆H. In particular, severity of strain localization during necking scaled linearly with ∆H. This study thus brought out a potential relationship among the phase hardness differential (∆H), severity of strain localizations and post-necking ductility (εNU).
Original languageEnglish
Pages (from-to)4018-4032
Number of pages15
JournalMetallurgical and materials transactions. A, Physical metallurgy and materials science
Issue number9
Early online date15 Jul 2021
Publication statusPublished - Sept 2021

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