Papers by Keyword: Boride

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Authors: Lin Lin Yuan, Jing Tao Han, Jing Liu
Abstract: Hard and brittle (Fe,Cr)2B phase caused by excess boron in high boron alloyed stainless steel has adverse effects on the hot working performance and mechanical properties of material. Adding Ti into high boron alloyed stainless steel can improve the type, morphology and distribution of boride phase. The results show that TiB2 phase with petals or small block shape forms after adding Ti into high boron alloyed stainless steel, and as the increase of Ti content, TiB2 phase replaces (Fe, Cr)2B gradually. Moreover, the petal-like TiB2 phase becomes smaller and more granular after high temperature deformation, and the segregation of matrix composition is significantly weakened by the formation of TiB2 phase.
226
Authors: Z.X. Li, Xia Huang, L.C. Qi, Chun Xiao Cao
Abstract: The beneficial effects of boron addition on microstructure transformations and mechanical properties of γ-TiAl alloys were investigated. Two growth mechanisms of boride (TiB2) in γ-TiAl alloy were confirmed, the curved flaky borides are products of irregular eutectic reaction growing coupled with matrix, while some faceted blocky borides in boron-rich alloy are primary TiB2 phase growing directly in melt. The core of flaky TiB2 is ultra-fine B2 phase and there has an orientation relationship [1210] TiB2//[001]B2, (1010) //(010)B2. In addition to the well-known grain refinement effect, boron addition can suppress the formation of metastable feathery and Widmastätten structure and broadens cooling-rate-range for the formation of fully lamellar structure, consequently, it improves thermal stability of the lamellar structure and accordingly prolongs the creep rupture life significantly. Another beneficial effect of boron addition is that boride can restrain discontinuous coarsening on lamellar grain boundary by pinning action and accelerates recrystallization of γ grain by introducing TiB2/matrix interfaces as nuclear sites during homogeneous treatment at 1150°C. Therefore, compared with boron-free alloy more homogeneous and refined near γ microstructure can be obtained in boron modified alloy.
1451
Authors: Osvaldo Flores, Juan M. Zagal, Antonio Contreras-Cuevas, G. Rosas, Ramiro Pérez, L. Martínez
Abstract: The microstructure of FeAl40 intermetallic alloy produced by spray atomization and deposition, with boron additions and reinforced with Al2O3 particles was studied. This technique allowed the co-deposition of particulate reinforcement and the addition of boron in order to obtain a boron concentration of 0.4 at. %. The additions of alumina particles produce a grain refinement. High resolution transmission electron microscopy observations shows a precipitation of boron in the FeAl matrix in despite of the rapid solidification process. Fe3B precipitates were found which is a metastable phase formed during the rapid solidification process. In addition, FeB precipitates were observed.
96
Authors: Jian Hong Gong, Shu Xia Lin, Jun Gao
Abstract: Boride inclusions in the synthetic diamond single crystals grown from Fe-Ni-C-B system under high temperature and high pressure were studied in the present paper. Both chemical composition and structure of the inclusions incorporated into the diamond during the process of diamond growth were successfully determined by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). It was found that the inclusions related to boron trapped in the diamond consisted of f.c.c. (FeNi)23(CB)6, (FeNi)3(CB), Fe2B, FeB, hexagonal Ni3B, and B4C.
101
Authors: Da Wei Yi, Jian Dong Xing, Han Guang Fu, Sheng Qiang Ma, Zhu Xin Liu
Abstract: This study investigates the effect of rare earth and aluminium composite modification on the structural variations of as-cast and heat treated medium carbon Fe–B cast alloys. The as-cast microstructure of Fe–B cast alloy consists of the eutectic boride, pearlite, martensite and ferrite. Moreover, compared to a netlike distribution of the coarse eutectic borides in the unmodified alloy, the eutectic boride structures in the modified alloy are greatly refined and less interconnected. After heat treatment, the phases in Fe–B cast alloy consist of the boride and martensite. The addition of rare earth helps to increase the number of the rod-shaped and round borides in Fe-B cast alloy during austenitizing. Compared to the unmodified alloy, the boride volume fraction and Rockwell hardness of the modified alloy have no significant change, however, the average area of each boride in the modified alloy is lower and the impact toughness is higher.
213
Authors: Jing Liu, Ke Zhang, Jing Tao Han
Abstract: High boron alloyed stainless steel(HBASS) with different Ti content were fabricated by vacuum induction furnace and their microstructure and boride phase were analyzed. The boride phase of HBASS do not contain Ti element is mainly (Fe,Cr)2B phase with slender rod-shape. After adding Ti into steel, because Ti and B preferentially combines into TiB2 phase with petals or small block shape which can stop the formation of hard and brittle (Fe,Cr)2B, so the number of (Fe,Cr)2B phase is reduced. And after adding Ti, many crisscross cracks appeared in internal large (Fe,Cr)2B phase, which will be effective to break into small pieces of boride to improve steel plasticity and shielding thermal neutron performance during hot rolling process.
738
Authors: Jian Jun Zhang, Yi Min Gao, Jian Dong Xing, Sheng Qiang Ma, Ye Fei Li, Li Liu
Abstract: The effects of forging and heat treatment on microstructure and properties of high boron white cast iron were investigated in this paper. The results show that forging breaks up boride network and makes broken boride particles uniformly distributed in matrix. During subsequent heat treatment, spheroidized boride is able to be obtained. The hardness of high boron white cast iron increases slightly (from 51.4 HRC to 54.7 HRC) while the toughness increases obviously (from 5 J/cm2 to 107 J/cm2) by combined process of forging and heat treatment. Fracture morphology changes from brittle fracture to ductile fracture.
225
Authors: Dong Jin Kim, Hyuk Chul Kwon, Seong Sik Hwang, Hong Pyo Kim, Jang Yul Park
Abstract: Corrosion-resistant nickel-based Alloy 600 is susceptible to a lead-induced stress corrosion cracking (PbSCC) in aqueous solutions. The lead species incorporated into the oxide at the alloy surface degraded the passivity, and caused the PbSCC. Effects of lead on the properties of the surface passive films were investigated. The cross sections of the surface films were examined by the transmission electron microscopy and the species present in the films were analyzed with the energy dispersive x-ray spectroscopy and the x-ray photoelectron spectroscopy. In-depth concentration profiles of the species were analyzed by using an ion sputtering technique. The electrochemical impedance spectroscopy technique was used to characterize the electrochemical behaviors. Effectiveness of a nickel boride inhibitor was evaluated. The boride inhibitor altered the properties of the passive film, and significantly reduced the susceptibility to the PbSCC.
1466
Authors: Li Jun Han, Yong Quan Chai, Chang Qing Jin
Abstract: . The accurate first-principle method was used to calculate the electronic structures of the four boride superconductors. Their DOS (the density of states), band structures as well as their specific electronic structures were discovered. It was found that they all had a metallic band crossing the Fermi surface on the Γ point. These characters made their attribute of superconductivity and the interstics of NbB was the least which resulted in its higher Tc than the others.
71
Authors: G.S. Choi, Y.H. Kim, S.S. Kang, Yeon Gil Jung, J.H. Lee, S.H. Rye
Abstract: The behavior of boride formation has been examined with solidification rates and boron contents by observing the solid/liquid interface using directional solidification in Mod. 12Cr-1Mo alloys. The phase transformation temperatures of liquidus, solidus, eutectic formation, and final solidification were analyzed by DTA. In order to analyze the crystallographic structure of the boride, extractive method, extracting the boride from the matrix, was used. The boride was proved as M3B2, and this boride phase expected to be formed by eutectic reaction. It has been also found that the boride formation depends on contents of born as well as the other alloying elements, such as C and W. As increasing boron contents, the amount of boride eutectic increased. Also, the alloying element W was shown to enhance the formation of the boride.
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