Examination of Galvanic Action between Fe-Based Bulk Metallic Glass and Crystalline Alloys
- PDF / 437,563 Bytes
- 10 Pages / 593.972 x 792 pts Page_size
- 57 Downloads / 212 Views
I.
INTRODUCTION
BULK metallic glasses (amorphous metals) are an emerging class of alloys in which there is great interest, due to the ability of these alloys to be designed for special properties. While all metallic glasses do not necessarily have high corrosion resistance, recent reviews document substantial progress in the development of corrosionresistant alloys.[1–3] Metallic glasses with interesting physical, mechanical, and corrosion properties have been studied for several decades. However, one of the challenges for fabricating amorphous alloys is that they typically require extremely high cooling rates, to avoid crystallization on cooling. Advances in overcoming this challenge have been made in both alloy composition design and fabrication technology innovation. Success in the fabrication of Fe-based amorphous metals was reported as early as 1967 by Duwez and Lin, with a ternary system of Fe-P-C.[4] However, the range of composition to form amorphous phase was relatively narrow (several atomic percent), and the critical cooling rate was high (106 K/s).[5] With the introduction of the concept of multicomponent alloy systems, Fe-based bulk metallic glass was made in 1995 by Inoue.[6] HUNG M. HA, Graduate Student, and JOE H. PAYER, Professor, are with the Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH. Contact e-mail: [email protected] This article is based on a presentation given in the symposium entitled ‘‘Iron-Based Amorphous Metals: An Important Family of High-Performance Corrosion-Resistant Materials,’’ which occurred during the MSandT meeting, September 16–20, 2007, in Detroit, Michigan, under the auspices of The American Ceramics Society (ACerS), The Association for Iron and Steel Technology (AIST), ASM International, and TMS. Article published online October 9, 2008 1334—VOLUME 40A, JUNE 2009
The addition of metalloid and transition metals is effective for the extension of the supercooled liquid region and reduces the critical cooling rate for the formation of amorphous phase. Recently, ingots 5 mm in diameter of (Fe80B20)-X amorphous alloys, where X is a refractory element such as Zr, Nb, Ta, W, or Mo, could be made without difficulty, using a copper mold.[7] In addition to developments in alloy design, many developments have occurred in advanced technologies that attempt to meet the requirement of a rapid cooling rate, including melt spinning, arc melting with drop casting, thermal spraying, chemical and physical vapor deposition, electrodeposition, ion-beam mixing, laser pulsing, etc.[1–3] Thermal-spray coating is a process that holds promise for applying amorphous metal alloy on metal structures, for erosion and corrosion resistance. The thermal-spray process is enhanced via the careful selection of the powder size and process temperature, to enable the production of coatings that have a glassy structure and good bond strength and are virtually pore free.[8] The thickness of the coatings may vary in the range of several hundreds of microns. Iron-base
Data Loading...
