Internal Stress and Elastic Strain Energy in Pearlite and Their Accommodation by Misfit Dislocations

Nakada, Nobuo; Kato, Masaharu

doi:10.2355/isijinternational.isijint-2016-256

Cited by 18 publications

(11 citation statements)

References 32 publications

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“…26) Thus, authors proposed that the internal stress generated by the misfit between ferrite and cementite has large influence on the strength of pearlite steels. [26][27][28][29][30][31] Figure 12 shows X-ray (211) ferrite diffraction peak containing Kα1 and Kα2 of 40C0Mn and 100C2Mn with IF steel as a reference. As shown above in Table 2, 40C0Mn and 100C2Mn have the lowest and highest 0.2% proof stress, respectively.…”

Section: Strength Mechanism Of Pearlite By Mn Additionmentioning

confidence: 99%

Effects of Mn on Isothermal Transformation Microstructure and Tensile Properties in Medium- and High-carbon Steels

et al. 2019

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The effects of Mn addition on the microstructure formed through an isothermal transformation at 873 K and its tensile properties were investigated over a wide range of concentrations in medium-and highcarbon steels with 0.4-1.0 mass% C. The Mn addition changed the pearlite transformation mode from relatively slow non-partitioning pearlite with a small amount of proeutectoid ferrite to an extremely slow partitioning pearlite without any proeutectoid ferrite in the hypoeutectoid steel. The transformation rate of the partitioning pearlite associated with the Mn partitioning between ferrite and cementite in Fe-CM alloy was more than three orders of magnitude lower than the pearlite transformation in Fe-C binary alloy at a given interlamellar spacing. The decrease in the transformation rate in the non-partitioning and partitioning pearlite transformation was caused by the decrease in the carbon flux controlling the pearlite transformation, which can be explained by the theory of local equilibrium at the austenite/ferrite and austenite/ cementite interphases. The Mn addition increased the thermal stability of the lamellar cementite. Corresponding to the change in the transformation microstructure, the Mn addition improved the tensile properties in the pearlite steel, particularly the strength and local deformability balance, regardless of the difference in the transformation mode between the non-partitioning and the partitioning transformation, unless the proeutectoid cementite precipitated at prior austenite grain boundaries. The strength increase of the pearlite after the Mn addition was caused by the refinement of the interlamellar spacing and/or the increase of the lattice strain in the pearlitic ferrite.

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Section: Strength Mechanism Of Pearlite By Mn Additionmentioning

confidence: 99%

Effects of Mn on Isothermal Transformation Microstructure and Tensile Properties in Medium- and High-carbon Steels

et al. 2019

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“…Recently, Nakada and Kato have evaluated such interface stress generation and its relaxation by introduction of misfit dislocations using a micro-mechanics model. 29)…”

Section: Pearlite Transformation and Change In Ferritementioning

confidence: 99%

<i>In situ</i> Neutron Diffraction Study on Ferrite and Pearlite Transformations for a 1.5Mn-1.5Si-0.2C Steel

et al. 2018

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The phase transformation behavior from austenite upon cooling in a 1.5Mn-1.5Si-0.2C steel was in situ monitored using dilatometry, X-ray and neutron diffractions. The starting temperature of ferrite transformation was in good agreement between dilatometry and neutron diffraction, whereas much higher in X-ray diffraction. Such a discrepancy in transformation temperature is attributed to the change in chemical composition near the surface of a specimen heated to elevated temperatures in a helium gas atmosphere for X-ray diffraction. In situ neutron diffraction enables us to investigate the changes in lattice constants of ferrite and austenite, which are affected by not only thermal contraction but also transformation strains, thermal misfit strains and carbon enrichment in austenite. Pearlite transformation started after carbon enrichment in austenite reached approximately 0.7 mass% and contributed to diffraction line broadening.

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“…Nakada and Kato estimated the elastic strain due to the misfit between ferrite and cementite by a calculation using micromechanics. 27) They suggested that the elastic strain energy changes according to the crystal orientation relationship and the lattice parameter gap due to distribution of alloying elements between the two phases. 28) To consider the effect of V distribution on the lattice strain, we attempted to evaluated the principal strain and elastic strain energy of the misfit based on the literature data.…”

mentioning

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“…28) To consider the effect of V distribution on the lattice strain, we attempted to evaluated the principal strain and elastic strain energy of the misfit based on the literature data. 27) The lattice parameter data of cementite (Fe 3 C) and its alloyed counterparts, which were studied by Razumovskiy and Ghosh using first-principles calculation, 29) were referred. Here, the cementite lattice parameters are a θ , b θ , and c θ , in ascending order.…”

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Lattice Strain and Strength Evaluation on V Microalloyed Pearlite Steel

et al. 2020

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The strengthening mechanism of microalloyed vanadium (V) on eutectoid pearlite steel was investigated from the perspectives of nano-precipitation and lattice strain. The 0.2% proof stress of specimens, isothermally transformed at 873 K, increased by about 160-170 MPa with the addition of 0.1% V. However, the interphase precipitation of vanadium carbide (VC), regarded as the principal strengthening factor, was detected neither by transmission electron microscopy nor by 3D atom probe microscopy (3D-AP). A lattice strain in lamellar ferrite, analyzed by broadening of the X-ray diffraction peak, has been experimentally estimated to understand the strengthening mechanisms by V-addition. The lattice strain data of 0.1% V-added pearlite specimens were plotted on the same correlation line as those of the V-free specimens with proof stress. In addition, the elemental map obtained by 3D-AP showed that V atoms concentrate in lamellar cementite rather than ferrite, which could change the cementite lattice parameters and gain ferrite/cementite misfit, causing lattice strain increment. These results revealed that microalloyed V influences not only VC precipitation in lamellar ferrite but also the lattice strain increment in pearlite lamellar. In the case of pearlite steels containing at most 0.1% V, lattice strain was considered the major factor of their yield behaviors. Furthermore, 0.1% V addition did not enhance work-hardening behavior as notably as that estimated by Ashby's work-hardening theory of dispersion-hardened crystals. Therefore, VC precipitation is not necessary for the V strengthening effect on pearlite steel.

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Internal Stress and Elastic Strain Energy in Pearlite and Their Accommodation by Misfit Dislocations

Cited by 18 publications

References 32 publications

Effects of Mn on Isothermal Transformation Microstructure and Tensile Properties in Medium- and High-carbon Steels

Effects of Mn on Isothermal Transformation Microstructure and Tensile Properties in Medium- and High-carbon Steels

<i>In situ</i> Neutron Diffraction Study on Ferrite and Pearlite Transformations for a 1.5Mn-1.5Si-0.2C Steel

Lattice Strain and Strength Evaluation on V Microalloyed Pearlite Steel

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