Corrosion And Electrochemical Properties Of Bulk Metallic Glasses And Nano Crystalline Materials

Author :
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (614 download)

DOWNLOAD NOW!

Download or read book The Mechanical and Electrochemical Properties of Bulk Metallic Glasses written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Bulk metallic glasses (BMGs) represent an emerging class of materials with an amorphous structure and a unique combination of properties. Some of these outstanding properties include exceptionally high strength, large elastic deformation, near-net-shape formability, and superplasticity. However, these materials are not commonly used in structural applications because of a lack of plasticity and a lack of clarity in terms of deformation and failure mechanisms. Furthermore, the electrochemical behavior of these materials with and without loading is not well defined. Thus, the objectives of this study were to define and model the electrochemical and mechanical behaviors of BMGs, in addition to the interactions between these. The electrochemical behaviors of Zr-, Ti- and Ca-based BMGs have been studied in various environments. Moreover, the electrochemical behaviors of several common, crystalline materials have also been characterized in the same environments to facilitate comparisons. In general, the Zr- and Ti-based BMG alloys demonstrated relatively good general corrosion resistance in all of the environments. Mean corrosion penetration rates (CPRs) were found to be less than 30 [mu][micrometer]/year for these alloys. On the other hand, the Ca-based BMG alloys were found to be highly active with CPRs ranging from 300 - 5700 [mu][micrometer]/year in a non-aggressive 0.05 M Na2SO4 electrolyte. Furthermore, most of these alloys were found to be susceptible to localized corrosion in these environments. However, the Zr- and Ti-based BMG alloys exhibited relatively high, positive values for both pitting overpotentials ... and protection overpotentials ... The Zr-based BMG commonly known as Vitreloy 105 (Vit 105) was selected for further studies. This material was fabricated at the Oak Ridge National Laboratory by arc-melting and drop-casting into a water-cooled, copper mold. Mechanical characterization of this alloy was conducted through four-point bend fatigue testing, as well as tensile testing with in situ thermography. Fatigue testing in air revealed that both the fatigue lives at various stresses and the fatigue endurance limit are similar to those reported for this material in uniaxial fatigue. This result alone demonstrates that the great differences in fatigue results reported in the literature are not due to differences in testing geometry. In fact, the larger scatter observed in four-point bend fatigue at a given stress range was found to be due to variations in material quality.