Search

The microstructure and oxidation behavior of Fe–B alloys have been investigated. Oxide scale cross-sectional microstructures oxidized at 1073 K for 100 h have been studied. EPMA investigations show that B 2 O 3 –SiO 2 oxides accumulates in the inner oxide layer which improves the oxidation behavior and oxide layer adhesion considerably. Cyclic oxidation kinetics data indicates that Fe–B 3.08 wt.% alloy presents the best oxidation resistance. The formation of diffusion zone in the Fe–B alloys indicate that the oxidation of the Fe 2 B boride is controlled by boron diffusion. The diffusion zone increases with time and reaches a maximum width of 60–65 μm. [ABSTRACT FROM AUTHOR]

The solidification microstructure, crystallography of eutectic precipitations and mechanical properties of high boron steel with various aluminium and chromium concentrations have been investigated extensively in the present study, as the foundation of the further analysis about the corrosion and abrasion properties at elevated temperature. The experiment results indicate that the as-cast microstructures of test alloys mainly consist of a dendritic matrix with many interdendritic precipitations. The Fe–B binary alloy is mainly composed of ferrite, Fe 2 B and pearlite and the Fe–B–Al ternary alloy consists of α-(Fe, Al) solid solution, Fe 2 B and Fe 3 AlC 0.5 . When aluminium and chromium elements are added synchronously, the as-cast microstructure changes to α-(Fe, Al, Cr) solid solution, (Fe, Cr) 2 B boride, M 7 (C, B) 3 and M 23 (C, B) 6 borocarbides. Moreover, the nucleation and growth of M 7 (C, B) 3 borocarbide is adhere to (Fe, Cr) 2 B boride because of an interphase match between crystal plane (10 1 ( — ) 0) of M 7 (C, B) 3 and (010) of Cr-rich (Fe, Cr) 2 B. Alloy Fe-1.46 wt. % B-0.22 wt. % C-11.92wt. % Cr-8.73 wt. % Al shows the highest impact toughness value. The main fracture mode is brittle fracture of boride and tough fracture of matrix. [ABSTRACT FROM AUTHOR]

The microstructure and properties of Fe-1.50 wt%B-0.40 wt%C high-speed steel (i.e. High boron high-speed steel, HBHSS) containing various Al contents have been investigated. The results show that the microstructure of HBHSS is composed of martensite, a little M 6 (C,B) and a large number of eutectic M 2 B borides. With the increase of aluminum, the martensite can reduce and lots of ferrite and pearlite occur, while M 2 B boride is gradually refined and isolated. Meanwhile, most of aluminum is mainly segregated within the ferrite grains. The room tensile strength of the steel begins to decrease when Al content exceeds 0.6 wt%, whereas the fracture and impact toughness are remarkably enhanced. A little aluminum can maintain high-temperature tensile stress of the steel at 500 °C and simultaneously improve its elongation. The high-density dislocations can be formed within Al-segregated ferrite zone to exhibit the strengthening and toughening roles, and a possible orientation relationship between (Fe,Cr) 2 B and multi-component M 2 B is (110) (Fe,Cr)2B ∕∕ (110) M2B in the steels. [ABSTRACT FROM AUTHOR]

The effects of orientation and lamellar spacing on the interface microstructure and corrosion behavior of a directionally solidified (DS) Fe-B alloy in a hot-dip galvanization bath were investigated. The results indicated that the microstructure of the DS Fe-B alloy consisted of oriented α -Fe and Fe 2 B grains. The oriented Fe 2 B with [002] preferred growth orientation displayed low-angle grain boundaries on the Fe 2 B (001) basal plane. The DS Fe-B alloy with Fe 2 B vertical to the corrosion interface possessed the best corrosion resistance to liquid zinc owing to the formation of an interface-pinning multilayer induced by the Fe 2 B orientation. The epitaxially grown columnar ζ-FeZn 13 products were controlled by the geometric constraint of Fe 2 B grain orientation and size, and a mechanism model that explains the interfacial orientation-pinning behavior is discussed in detail. Transmission electron microscopy (TEM) results revealed that the possible orientation relationships of the oriented Fe 2 B and columnar ζ-FeZn 13 products are (001) Fe2B //(−402) ζ-FeZn13 and [002] Fe2B //[110] ζ-FeZn13 . The corrosion damage of the DS Fe-B alloy with Fe 2 B [002] orientation vertical to the corrosion interface in liquid zinc was governed by the competitive mechanisms of Fe 2 B/FeB transformation and microcrack-spallation resistance, which is proposed as being the result of a multiphase synergistic effect in the micro-structures. [ABSTRACT FROM AUTHOR]