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Development of novel binary and multi-component bulk metallic glasses

Citation

Xu, Donghua (2005) Development of novel binary and multi-component bulk metallic glasses. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-05272005-160315

Abstract

Bulk Metallic Glasses (BMGs) have been drawing increasing attention in recent years due to their scientific and engineering significance. A great deal of effort in this area has been devoted to developing BMGs in different alloy systems. BMGs based on certain late transition metals (e.g. Fe, Co, Ni, Cu) have many potential advantages over those based on early transition metals. These include even higher strength and elastic modulii, and lower materials cost, to name a few, which are highly preferable for a broad application of BMGs as engineering materials. Nevertheless, these ordinary-late-transition-metal-based BMGs generally have quite limited glass-forming ability (GFA). In particular, for the Ni-based and Cu-based alloys reported prior to this research, the maximum casting thickness allowed to retain their amorphous structures is only ~2 mm (or lower) and ~5 mm (or lower), respectively.

During this research it was first found that certain quinary Ni-based alloys in the Ni-Cu-Ti-Zr-Al system can be cast into 5 mm diameter amorphous rods. This critical casting thickness is the highest for any reported Ni-based BMG’s indicating that these alloys are the easiest metallic glass formers based on Ni discovered to date. Secondly, certain binary alloys in the Cu-Zr and Cu-Hf systems were found to form bulk glasses with casting thickness as high as 2 mm. The discovery of these binary BMGs was very surprising since it had been widely considered that only multi-component (containing at least three elements) alloys could form bulk metallic glasses. These new binary BMGs provide interesting subjects for future theoretical studies such as molecular dynamics simulations since they possess both the simplicity of binary alloys and the good GFA of multi-component BMGs. In fact, these binary BMGs have led to the third but perhaps the most significant progress during this research, i.e., the discovery of a family of Cu-based BMGs in the Cu-Zr-Al-Y system which possess a critical casting thickness up to 1 cm. These quaternary Cu-based alloys, together with some complicated Fe-based alloys reported by two other groups during the course of this research, are the first centimeter level BMGs based on the ordinary late transition metals.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:amorphous alloys; bulk metallic glasses; Cu alloys; mechanical properties; Ni alloys; nucleation
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Materials Science
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Johnson, William Lewis
Thesis Committee:
  • Johnson, William Lewis (chair)
  • Ravichandran, Guruswami
  • Nicolet, Marc-Aurele
  • Goddard, William A., III
Defense Date:17 May 2005
Author Email:xudh (AT) caltech.edu
Record Number:CaltechETD:etd-05272005-160315
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-05272005-160315
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2158
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:31 May 2005
Last Modified:26 Dec 2012 02:47

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