The influence of martensite shape, concentration, and phase transformation strain on the deformation behavior of stable dual-phase steels

Journal Article · Mon Feb 01 04:00:00 EST 1993 · Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States)

DOI:https://doi.org/10.1007/BF02657317· OSTI ID:6311320

Bhattacharyya, A; Weng, G J ^[1]; Sakaki, T ^[2]

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1. Rutgers Univ., New Brunswick, NJ (United States)
2. Tokyo Metropolitan Univ. (Japan)

A continuum model is developed to examine the influence of martensite shape, volume fraction, phase transformation strain, and thermal mismatch on the initial plastic state of the ferrite matrix following phase transformation and on the subsequent stress-strain behavior of the dual-phase steels upon loading. The theory is developed based on a relaxed constraint in the ductile matrix and an energy criterion to define its effective stress. In addition, it also assumes the martensite islands to possess a spheroidal shape and to be randomly oriented and homogeneously dispersed in the ferrite matrix. It is found that for a typical water-quenched process from an intercritical temperature of 760 C, the critical martensite volume fraction needed to induce plastic deformation in the ferrite matrix is very low, typically below 1 pct, regardless of the martensite shape. Thus, when the two-phase system is subjected to an external load, plastic deformation commences immediately, resulting in the widely observed 'continuous yielding' behavior in dual-phase steels. The subsequent deformation of the dual-phase system is shown to be rather sensitive to the martensite shape, with the disc-shaped morphology giving rise to a superior overall response (over the spherical type). The stress-strain relations are also dependent upon the magnitude of the prior phase transformation strain. The strength coefficient h and the work-hardening exponent n of the smooth, parabolic-type stress-strain curves of the dual-phase system also increase with increasing martensite content for each selected inclusion shape. Comparison with an exact solution and with one set of experimental data indicates that the theory is generally within a reasonable range of accuracy.

• OSTI ID: 6311320
• Journal Information: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Journal Name: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States) Vol. 24:2; ISSN 0360-2133; ISSN MTTABN
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
ALLOYS
ANNEALING
CARBON ADDITIONS
DEFORMATION
DUCTILITY
FERRITE
HEAT TREATMENTS
IRON ALLOYS
IRON BASE ALLOYS
MARTENSITE
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
PHASE TRANSFORMATIONS
PLASTICITY
SHAPE
STEELS
STRAINS
STRESSES
TENSILE PROPERTIES