Corrosion and related mechanical properties of bulk metallic glasses
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A. Gebert Leibniz Institute for Solid State and Materials Research IFW Dresden, D-01171 Dresden, Germany
Joe H. Payera) Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106-7204 (Received 22 August 2006; accepted 15 November 2006)
The review of corrosion performance of a number of alloy systems documents several metallic glasses with corrosion resistance superior to that of crystalline metals. In other cases, the metallic glasses do not have superior corrosion resistance. The nature of corrosion resistance of the metallic glasses is often directly related to the development of a passive film (protective layer) on the reactive alloy substrate, increased durability of the passive film, or enhanced resistance to localized corrosion where the passive film is broken or damaged. Potential mechanical/environmental degradation processes include stress-corrosion cracking, corrosion fatigue, various forms of hydrogen damage, wear, and abrasion. The availability of bulk metallic glasses in significant three-dimensional sizes will stimulate important work in these areas that will enhance the fundamental understanding of the corrosion behavior and mechanical interactions and develop design guidelines and materials properties database for designers and engineers.
I. INTRODUCTION
This paper focuses on the corrosion behavior of metallic glasses (amorphous metals). A recent review provides an overview of the corrosion of metallic glasses1 while the objective here is to provide a corrosion perspective to the interactions between mechanical properties and exposure to aqueous environments. The glassy metals have provided a new and exciting class of materials since their introduction in the late 1960s.2 They provide a special opportunity for the design and control of structural, mechanical, electronic, magnetic, and corrosion properties.3,4 The early metallic glasses were produced from two or more transition metals or from a combination of metals and metalloids, e.g., Cu–Zr and Fe–Ni–Cr/B–P–C, respectively. These early alloys required extremely rapid cooling rates (>105 K/s) to attain a highly metastable, glassy state. Consequently, the forms of the glassy alloys were restricted to thin ribbons, wires, and flakes/powders a)
Address all correspondence to this author. e-mail: [email protected] DOI:10.1557/JMR.2007.0051 302 J. Mater. Res., Vol. 22, No. 2, Feb 2007 http://journals.cambridge.org Downloaded: 01 Jun 2014
produced with an extremely rapid quench rate, and the as-produced materials were subject to devitrification at modest temperatures. More recently, over the last ten to fifteen years, a number of metallic glasses with much lower critical cooling rates have been discovered.3,5–7 With critical cooling rates as low as 1 K/s, these alloys can be produced with thicker cross sections. These multicomponent metallic alloys with high glass-forming ability allow for the production of three-dimensional shapes with a glassy structure. Thus the term “bulk metallic glasses” (BMG) is
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