The interfaces and erosion of oriented Fe-B alloy in flow zinc at various erosion angles were investigated. The results indicate that oriented Fe-B alloy exhibits better erosion resistance at 90 degrees erosion. Erosion angle can strongly affect erosion resistance, which depends on not only the interfacial structure but also the epitaxial zeta accumulation. Meanwhile, cavitation erosion pits and interface spallation occur, which may be suppressed by zeta accumulation at 90 degrees erosion, thus strengthening the adhesion of product films. (c) 2017 Elsevier B.V. All rights reserved.

The effects of erosion angle and Fe2B orientation on cavitation erosion and interface structures of a directionally solidified (DS) Fe-B alloy in flowing liquid zinc were investigated to clarify erosion mechanism of liquid metal. The results indicate that the cavitation erosion rate of DS Fe-B alloy with Fe2B [001] orientation vertical to interface exhibits better erosion cavitation resistance. Erosion angle can strongly affect erosion performance that depends not only on interfacial orientation structure but also on local microturbulence. Erosion morphologies manifest that an obvious cavitation erosion occurs in strong flowing zinc disturbed and agitated zone, which results in severe cavitation pits and slip deformation of products, thus stimulating subsequent localized corrosion and pit-aggregation cracks. Cavitation erosion craters coupled with performance variations confirm that microturbulence-assisted fluid eddies and backflow are responsible for the cavitation pits. The combined effects of flow pattern and interface orientation significantly govern the epitaxial grown ζ removal/accumulation behaviors and multiphase pinning film adhesion. A model of hydraulic liquid-hammer action by cavitation-induced microjet and interface orientation interaction is proposed and discussed to account for cavitation pits and slip cracking, which reveals underlying erosion mechanism and material design of DS Fe-B alloy in flowing liquid zinc.

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 M2B borides. With the increase of aluminum, the martensite can reduce and lots of ferrite and pearlite occur, while M2B 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 degrees 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 M2B is (110)((Fe,Cr)2B) // (1.10)(M2B) in the steels. (C) 2017 Elsevier B.V. All rights reserved.

The microstructure and age-hardening behavior of a new kind of Al-modified low carbon high boron high-speed steel (BHSS) were investigated. The results show that the as-cast microstructure of BHSS mainly consists of M2B borides and dendrite martensite. Al addition can promote the formation of pearlite and ferrite. After heat treatment, proper Al addition can not only remarkably increase the bulk hardness of BHSS during destabilized condition, but also promote the subsequent precipitation-hardening effect. The tempered BHSS with 0.6wt%Al exhibits the best precipitation-hardening behavior at 520°C tempering, which is attributed to the presence of some dispersive M23(B,C)6 and M6(B,C) secondary precipitations. The proper Al can promote the formation of M7(B,C)3 and inhibit the coalescence of secondary precipitations. TEM analysis indicates that there exists an orientation relationship of (112)M23(B,C)6//(112)M6(B,C) in the steels.