Pre-strain effects on critical stress and hydrogen content for hydrogen-induced quasi-cleavage fracture in a TRIP-aided bainitic ferrite steel: Martensitic transformation, matrix damage, and strain aging

This paper examined whether the modified Ritchie-Knott-Rice (RKR) failure criterion can be applied to examine the feasibility of miniaturized Charpy type SE(B) specimens of thickness-to-width ratio B/W=1. The modified RKR failure criterion considered in this paper is the (4δt,σ22c) criterion which predicts the onset of cleavage fracture when the midplane crack-opening stress measured at a distance equal to four times the crack-tip opening displacement, denoted as σ22d, exceeds a critical stress σ22c. Specimens with B values of 25, 10, 3, and 2 mm (denoted as 25t, 10t, 3t, and 2t specimens, resp.) manufactured with 0.55% carbon steel were tested at 20°C. The results showed that the modified RKR criterion could appropriately predict the occurrence of cleavage fracture accompanied by negligibly small stable crack extension (denoted as KJc fracture) naturally for the 25t and 10t specimens. The modified RKR criterion could also predict that KJc fracture does not occur for the 2t specimen. The σ22c obtained from specimens for the 25t and 10t specimens exhibited only a small difference, indicating that the Jc obtained from the 10t specimens can be used to predict the Jc that will be obtained with the 25t specimens.

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Effects of thermomechanical treatments on the martensitic transformation and critical stress of Ti–50.2at.% Ni alloy

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2015.02.195 ◽

2015 ◽

Vol 637 ◽

pp. 171-177 ◽

Cited By ~ 7

Author(s):

M. Karimzadeh ◽

M.R. Aboutalebi ◽

M.T. Salehi ◽

S.M. Abbasi ◽

M. Morakabati

Keyword(s):

Martensitic Transformation ◽

Critical Stress ◽

Ni Alloy

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Thermal stability of retained austenite in bainitic steel: an in situ study

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2011.0212 ◽

2011 ◽

Vol 467 (2135) ◽

pp. 3141-3156 ◽

Cited By ~ 57

Author(s):

A. Saha Podder ◽

I. Lonardelli ◽

A. Molinari ◽

H. K. D. H. Bhadeshia

Keyword(s):

Martensitic Transformation ◽

Retained Austenite ◽

Elevated Temperatures ◽

Bainitic Ferrite ◽

Ambient Conditions ◽

Two Phase ◽

Tempering Temperature ◽

Thermal Stability Of ◽

Lower Carbon

The tempering of two-phase mixtures of bainitic ferrite and carbon-enriched retained austenite has been investigated in an effort to separate the reactions that occur at elevated temperatures from any transformation during cooling to ambient conditions. It is demonstrated using synchrotron X-radiation measurements that the residue of austenite left at the tempering temperature partly decomposes by martensitic transformation when the sample is cooled. It is well established in the published literature that films of retained austenite are better able to resist stress or strain-induced martensitic transformation than any coarser particles of austenite. In contrast, the coarser austenite is more resistant to the precipitation of cementite during tempering than the film form because of its lower carbon concentration.

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Effect of Strain-Induced Martensitic Transformation on Coaxing Effect of Austenitic Stainless Steels

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.385-387.505 ◽

2008 ◽

Vol 385-387 ◽

pp. 505-508

Author(s):

Jae Woong Jung ◽

Masaki Nakajima ◽

Yoshihiko Uematsu ◽

Keiro Tokaji ◽

Masayuki Akita

Keyword(s):

Martensitic Transformation ◽

Stainless Steels ◽

Work Hardening ◽

Strain Aging ◽

Austenitic Stainless Steels ◽

Fatigue Tests ◽

The Other ◽

Conventional Tests ◽

Materials Used ◽

Type 304

The effects of martensitic transformation on the coaxing behavior were studied in austenitic stainless steels. The materials used were austenitic stainless steels, type 304 and 316. Conventional fatigue tests and stress-incremental fatigue tests were performed using specimens subjected to several tensile prestrains from 5% to 60%. Under conventional tests, the fatigue strengths of both steels increased with increasing prestrain. Under stress-incremental tests, 304 steel showed a marked coaxing effect, where the failure stress significantly increased irrespective of prestrain level. On the other hand, the coaxing effect in 316 steel decreased with increasing prestrain up to 15%, where the failure stresses were nearly the same. Above this prestrain level, the coaxing effect increased with increasing prestrain. In 304 steel, the coaxing effect is primarily dominated by work hardening at low prestrains, while the effect of strain-induced martensitic transformation increases with increasing prestrain. The coaxing effect in 316 steel is dominated by both work hardening and strain aging at low prestrains, but strain-induced martensitic transformation could play a significant role at high prestrains.

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