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High Strength Steels
Published in P. C. Angelo, B. Ravisankar, Introduction to Steels, 2019
By inoculating molten steel with controlled additions of nonmetallic particles, bainite can be induced to nucleate intragranularly on the inclusions, rather than from the austenite grain surfaces. This intragranularly nucleated bainite is called “acicular ferrite.” It is a much more disorganized microstructure with a larger ability to deflect cracks. Inoculated steels are now available commercially and are being used in demanding structural applications such as the fabrication of oil rigs for hostile environments.
Titania-silica Composite with Photocatalytic Properties and Its Application on Brazilian Granite and Sandstone
Published in International Journal of Architectural Heritage, 2023
Danielle Grossi, Dolores Ribeiro Ricci Lazar, Eliane Aparecida Del Lama, Valter Ussui
TiO2 has three polymorphs: anatase and rutile, belonging to a tetragonal crystal system, and brookite, which has an orthorhombic symmetry. Of the three, the polymorphs most commonly used in stone-building conservation are anatase, rutile, and mixtures of the two in various proportions (Andronic et al. 2011; Pinho and Mosquera 2011, 2013). The rutile polymorph has yellowish acicular particles. Anatase has rounded, bluish-coloured particles and proves to be superior to rutile in terms of its larger surface area (Gherardi, Goidanish, and Toniolo 2018; Goffredo et al. 2017; Quagliarini et al. 2013), high concentration of active sites, greater electron mobility (Hanaor and Sorrell 2011; Kaleji et al. 2011), high transparency and photocatalytic activity, and slower electronic recombination (Nakajima et al. 2000). However, it has a larger band gap than rutile and is unstable at high temperatures (Feltrin et al. 2013), but this is not relevant to treating the surfaces of monuments, since they do not reach high temperatures even when exposed to intense solar radiation.
Experimental study on application of gas metal arc welding based regulated metal deposition technique for low alloy steel
Published in Materials and Manufacturing Processes, 2022
Din Bandhu, Jay J. Vora, Subhash Das, Ashish Thakur, Soni Kumari, Kumar Abhishek, M. Nagaphani Sastry
The presence of bainite (shown by the alphabet B) in a dark color and ferrite (represented by the alphabet F) in a lighter color can be seen in Fig. 4(a). A fine dispersion of alloy carbides such as M3C, M2C, M7C3, and M23C6 may also be detected in the microstructure, but owing to their short width, their distribution is not easily observable. Here, M denotes Fe, Cr, Mo, or a mix of these elements, whereas C denotes carbon. Fig. 4(b) shows a noticeable difference in microstructure from BM to HAZ. The existence of bainitic structure can be seen in the micrograph of unaffected base material, whereas HAZ microstructures reveal a mixture of fine and coarse grains. These grains resemble acicular bainite in appearance. The obtained microstructures are similar to the microstructures of Cr-Mo steel reported by Das et al.,[76] Ahmed et al.,[77] Juliermes et al.,[78] and Yoo, et al.[79] in their research of microstructure of Cr-Mo steel. They have characterized the presence of bainitic microstructure along with various carbide precipitates.
Quantitative analysis of microstructure and impact toughness in the simulated coarse-grained heat-affected zone of Cu-bearing steels
Published in Mechanics of Advanced Materials and Structures, 2019
Y. Liu, G.Q. Li, X.L. Wan, H. Gang, K.M. Wu, X. Zhang
It is well known that the impact toughness in the simulated CGHAZ of HSLA steel is usually influenced by prior austenite grain size, size of inclusion, and microstructure characteristic in steel after heat input welding thermal cycles [28]. In this work, the dramatic difference in toughness in the simulated CGHAZ of Cu-free and Cu-bearing steels with similar sizes of prior austenite grain and inclusion should be caused by the microstructure. Acicular ferrite is considered to be a desirable microstructure in the CGHAZ of HSLA steels as it contributes to excellent impact toughness. Acicular ferrite usually nucleates on intragranular non-metallic inclusion in large prior austenite grain and grows in various directions, and keeps high angle grain boundary with neighboring microstructure [29]. When small amount of acicular ferrite are formed in the simulated CGHAZ, the scattered acicular ferrite grains effectively partition the large austenite grain into many smaller and separate regions and confine the growth of later formed bainite with limited size. Finally, the fine-grained mixed microstructure of acicular ferrite and bainite are formed [30]. With the content of acicular ferrite increasing, abundant of primary acicular ferrite grains directly associate with intragranular inclusions also provide excellent sites for sympathetic nucleation of secondary acicular ferrite. The high density of acicular ferrite grains then impinge and intersect with the neighboring ferrite and form fine-grain and interlocked microstructures [1].