Post-uniform elongation and tensile fracture mechanisms of Fe-18Mn-0.6C-xAl twinning-induced plasticity steels

Synopsis : This paper presents an overview of the recent works on dynamic strain aging (DSA) of Fe-Mn-C austenitic steels including Hadfield and twinning-induced plasticity (TWIP) steels. First, a model of the DSA mechanism and its controlling factors are briefly explained in terms of Mn-C coupling and dislocation separation. Then, we introduce the effects of DSA on mechanical properties such as work hardening capability, uniform elongation, post-uniform elongation, and fatigue strength. Specifically, we note the pinning effect on extended dislocation for the work hardening, the Poretvin-Le Chatelier banding effect on damage evolution for the elongation, and the crack tip hardening/softening effect on crack resistance for the fatigue strength. We believe that this overview will help in designing advanced high-strength steels with superior ductility and fatigue resistance.

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“…Table 3. Reduction ratios of width, thickness and area between the uniformly deformed region and the fractured region after tensile tests 70) . …”

Section: セレーション開始ひずみの結晶粒径 " 逆 " 依存性mentioning

confidence: 99%

Overview of Dynamic Strain Aging and Associated Phenomena in Fe-Mn-C Austenitic Steels

2018

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“…Figure 7 shows SEM images of the specimen cross-sections after the thermal fatigue tests. The oxide layers formed during thermal fatigue are uneven and non-continuous, as observed in the literature [22]. These must result from the cyclic thermal stress and deformation in both the oxide layer and underlying steel.…”

Section: High Temperature Oxidationmentioning

confidence: 74%

Thermal Fatigue Characteristics of Type 309 Austenitic Stainless Steel for Automotive Manifolds

Zhan

Huang³

et al. 2019

Metals

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The thermal fatigue behavior of type 309 austenitic stainless steel was investigated by cyclic tests ranged from 100 • C to the maximum temperatures 800 and 900 • C. The microstructures of the specimens were characterized by optical microscope, scanning electron microscope and X-ray diffraction. With changing the maximum temperature from 800 to 900 • C, the stainless steel exhibits much lower strength, higher elongation and a decrease of fatigue life about 56.6%. After the thermal fatigue failure, the specimens show micro-void coalescence fractures caused by the creep during the holding period at the maximum temperatures, and the quasi-cleavage feature also appears in the case of the maximum temperature 800 • C. During the thermal fatigue processes, the cavities usually form at the grain and twin boundaries, facilitating the initiation and growth of cracks. Furthermore, the high-temperature oxidation produces oxides on the specimen surfaces and in the cracks, deteriorating thermal fatigue properties. With an increase in the maximum temperature, the enhanced synergetic effect of strength, grain size, creep and oxidation is responsible for the accelerated fatigue failure of 309 stainless steel during the thermal cycles.

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“…The magnification of deep dimple and shear fracture regions are presented in Figure d and g, respectively. In the other part of fracture, the stress and strain concentrations within the PLC band are strong, so the cracks rapidly propagate along the PLC band across the whole sample, leaving flat shear fracture, as shown in Figure g. With the deformation temperature increasing to 393 K, the fracture exhibits similar morphology, including deep dimple region, and shear fracture region.…”

Section: Resultsmentioning

confidence: 96%

“…The dynamic strain aging (DSA) effect is considered as the main cause, where the localized strain and stress concentrations appear within the Portevin‐le Chatelier (PLC) bands (promoted by DSA effect) . In order to suppress the harmful effect of DSA on the fracture behavior, the additions of Al, Si, and N into Fe–Mn–C system TWIP steel are investigated. However, these methods are not perfect, such as the Al addition reduces the tensile strength and work‐hardening rate, the Si addition lowers the ductility, and the N addition brings limited simultaneous improvement.…”

Section: Introductionmentioning

confidence: 99%

Dramatic Increase of Strength and Ductility in Fe–22Mn–1.0C Twinning‐Induced Plasticity Steel at Elevated Temperature

2018

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Tensile properties and microstructural evolutions of Fe-22Mn-1.0C (wt%) twinning-induced plasticity steel are investigated in the temperature range from 293 to 443 K. An unexpected enhancement of strength and ductility is observed at the elevated temperature of 443 K (%400 MPa ultimate tensile strength and %10% true strain improvements). The twinning capability is still kept stable with the increasing temperature, and the premature fracture is postponed by suppressing dynamic strain aging effect. As a result, the synchronous improvement of strength and plasticity is achieved at high deformation temperature.

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Post-uniform elongation and tensile fracture mechanisms of Fe-18Mn-0.6C-xAl twinning-induced plasticity steels

Cited by 52 publications

References 26 publications

Overview of Dynamic Strain Aging and Associated Phenomena in Fe-Mn-C Austenitic Steels

Overview of Dynamic Strain Aging and Associated Phenomena in Fe-Mn-C Austenitic Steels

Thermal Fatigue Characteristics of Type 309 Austenitic Stainless Steel for Automotive Manifolds

Dramatic Increase of Strength and Ductility in Fe–22Mn–1.0C Twinning‐Induced Plasticity Steel at Elevated Temperature

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