Crystal Orientation Relationships between Acicular Ferrite, Oxide, and the Austenite Matrix

Nako, Hidenori; Hatano, Hitoshi; Okazaki, Yuji; Yamashita, Ken; Otsu, Minoru

doi:10.2355/isijinternational.54.1690

Cited by 26 publications

(8 citation statements)

References 34 publications

(59 reference statements)

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“…This effect was first observed for weld metals. [8] Comprehensive reviews on the formation of acicular ferrite have been done by Bhadeshia [9] as well as Sarma et al [10] Up to now, C-Mn-(Ni) weld metals [11][12][13][14][15] were the most investigated material related to the formation of acicular ferrite.…”

Section: Introductionmentioning

confidence: 99%

On the Capability of Nonmetallic Inclusions to Act as Nuclei for Acicular Ferrite in Different Steel Grades

Loder

Michelic

Mayerhofer

et al. 2017

Metall Mater Trans B

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Acicular ferrite nucleates intragranularly on nonmetallic inclusions, forming a microstructure with excellent fracture toughness. The formation of acicular ferrite is strongly affected by the size, content, and composition of nonmetallic inclusions, but also by the composition of the steel matrix. The potential of inclusions in medium carbon HSLA (high-strength low-alloyed) steels has been the main focus in the literature so far. The current study evaluates the acicular ferrite capability of various inclusions types in four different steel grades with carbon contents varying between 0.04 and 0.65 wt pct. The investigated steels are produced by melting experiments on a laboratory scale and subsequent heat treatment in a High-Temperature Laser Scanning Confocal Microscope. Inclusions are exclusively formed by deoxidation and desulfurization reactions. No synthetic particles are added to the melt. The inclusion landscape is analyzed by Scanning Electron Microscopy. Final ductility of the samples is evaluated based on performed tensile tests. Inclusion types in every steel grade are assessed regarding their nucleation potential always considering the interaction with the steel composition, especially focusing on the role of manganese. The effects of (Ti,Al)O x -, MnS-, and MgO-containing inclusions are discussed in detail.

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Section: Introductionmentioning

confidence: 99%

On the Capability of Nonmetallic Inclusions to Act as Nuclei for Acicular Ferrite in Different Steel Grades

Loder

Michelic

Mayerhofer

et al. 2017

Metall Mater Trans B

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show abstract

“…Jiang et al also proposed the similar conclusions by the investigation about microstructure refinement and mechanical properties improvement by developing intra‐granular acicular ferrites on inclusions in Ti–Al complex deoxidized HSLA steel. It is also worth noting that, in contrast to Kang ’ s experimental results, Nako et al did not find the MDZ around the inclusions containing MnTi 2 O 4 constituent in their works about crystal orientation relationships between AF, oxide, and the austenite matrix in low carbon steel submerged‐arc welding weld.…”

Section: Introductionmentioning

confidence: 73%

Inclusion Characteristics and Acicular Ferrite Nucleation in Ti‐Containing Weld Metals of X70 Pipeline Steel

Wang

2017

steel research int.

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The X70 steel weld metals with Ti content of 0.003-0.13% are prepared by single pass submerged-arc welding process. The effects of Ti content in weld metals on the constituent phases of inclusions and potential of acicular ferrite nucleation on the inclusions are in detail investigated by means of electron probe micro-analysis, scanning transmission electron microscopy, and thermodynamic calculation. The obtained results show that with an increase of Ti content, primary constituent phases of inclusions are changed from (Mn-Al-Si-O) compound to a mixture of spinel and pseudobrookite solid solutions, eventually to pseudobrookite. The spinel solid solution is characterized by MnTi 2 O 4 constituent. The proportion of Ti 3 O 5 in pseudobrookite is increased remarkably with an increase in Ti content at the expense of MnTi 2 O 5 constituent. Compared with pseudobrookite, spinel has lower Ti concentration, but significantly higher Mn content regardless of Ti content in the weld metals. In the case of presence of a considerable amount of spinel primarily composed of MnTi 2 O 4 , Mn element is enriched strongly in the inclusions, resulting in the development of Mn-depleted zone in matrix around the inclusions, which enhances the capability of inclusions nucleating intragranular acicular ferrite.

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“…[20] Ti-deoxidation has been found as an effective way of promoting AF-nucleation effective particles, and it has been successfully implemented in steel industrial production. [4] Various inclusions after Ti-deoxidation have been found effective in stimulating AF nucleation, including MnTi 2 O 4, [21][22][23] TiO, [24,25] and Mn-Si-Al-Ti-O amorphous phases. [26] Despite the wide range of effective inclusions found…”

Section: Introductionmentioning

confidence: 99%

Acicular Ferrite Identification in Heat‐Affected Zone of a Ti‐Killed High Strength Low Alloy Steel

Zhao,

Gao,

Huang

et al. 2024

steel research int.

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It is frequently found in the literature that an acicular ferrite (AF) dominant microstructure has unsteady or even low‐impact toughness. It is necessary to analyze whether they are qualified for real AF. Herein, a Ti‐killed high strength low alloy steel is prepared and subjected to heat‐affected zones simulation tests to induce various AF‐like microstructures. The morphological differences of these microstructures are compared, and their crystallographic characteristics are analyzed. It is found that even within a single prior austenite grain, the transformed microstructure can be heterogeneous. Local areas having clear lath boundaries and a chaotic or interlocking morphology should be classified as AF. Adjacent laths in these areas are from different close‐packed plane and Bain groups. In contrast, local areas having vague lath boundaries and a granular‐bainite‐like morphology should be classified as granular bainite. Neighboring laths in these areas are from the same Bain group, and a relatively low density of high‐angle grain boundaries can be found. The heterogeneous microstructure consisting of granular bainite and AF has a wider grain size distribution and a higher area fraction occupied by large grains, which can lead to the scatter of Charpy impact energy. Criteria for the identification of AF are also proposed in this research.

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Crystal Orientation Relationships between Acicular Ferrite, Oxide, and the Austenite Matrix

Cited by 26 publications

References 34 publications

On the Capability of Nonmetallic Inclusions to Act as Nuclei for Acicular Ferrite in Different Steel Grades

On the Capability of Nonmetallic Inclusions to Act as Nuclei for Acicular Ferrite in Different Steel Grades

Inclusion Characteristics and Acicular Ferrite Nucleation in Ti‐Containing Weld Metals of X70 Pipeline Steel

Acicular Ferrite Identification in Heat‐Affected Zone of a Ti‐Killed High Strength Low Alloy Steel

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