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The influence of alloy composition and interfacial segregants on the fracture and fatigue of metal/ceramic interfaces

IP.com Disclosure Number: IPCOM000128100D
Original Publication Date: 1999-Dec-31
Included in the Prior Art Database: 2005-Sep-14
Document File: 10 page(s) / 34K

Publishing Venue

Software Patent Institute

Related People

Gaudette, Frederick G: AUTHOR [+3]

Related Documents

http://theses.mit.edu:80/Dienst/UI/2.0/Describe/0018.mit.theses/1999-37: URL

Abstract

The use of multi-layered composites in the aircraft, automotive, and electronics industries is becoming more common as performance requirements exceed the capabilities of homogeneous materials. As a result, the need to assess their failure is critical. Diffusion bonded joints, thermal-barrier and wear resistant coatings, and thin films in VLSI electronics are three examples. In each of these cases, elastic and plastic mismatch between layers, when combined with thermal and/or mechanical loading, results in geometry dependent failure modes. Through a combination of experimental studies and analytical/numerical modeling, key parameters that affect the fracture and fatigue resistances of metal/ceramic interfaces have been captured. Specifically, results from fracture and fatigue experiments conducted on vacuum diffusion bonded interfaces between A1203 and (i) Ni, (ii) ay-Ni alloy containing Cr and (iii) Al are presented along with numerical simulations of interface fracture in layered materials subjected to a monotonic variation in temperature. The influence of alloy composition, and the interdependence of impurity concentration and bonding state (liquid-phase/solid-state) on interface toughness and fatigue crack growth resistance are discussed, with important findings detailed as follows. i) Experimental studies designed to characterize the fracture resistance of interfaces between A1203 and either pure Ni or a 7-Ni alloy containing Cr have revealed a profound influence of Cr on the debond toughness. The interface between pure Ni and A1203 is susceptible to stress corrosion caused by moisture, resulting in a fracture energy of order 10 Jm-2. In contrast the interface between the alloy and the A1203 cannot be fractured, even at strain energy release rates in excess of 100 Jm-2. An analysis of these interfaces has identified two influences of the alloy addition that govern its role in eliminating stress corrosion: (1) Cr "; getters "; the C near the interface by forming a Cr-carbide reaction product, and (ii) the alloy dissolves some of the alumina during bonding, exposing virgin material to the alloy at the interface. The factors leading to carbide formation and alumina dissolution are discussed. ii) An investigation of the influence of bonding technique on the fatigue crack resistance of Ni(Cr) and A1203 interfaces has identified an important interdependence between sulfur impurity in the Ni(Cr) and bonding state. Solid-state diffusion bonded (SSDB) inter- faces are tough and fatigue resistant. Liquid-phase bonded (LPB) interfaces suffer from stress corrosion because of sulfur segregation. Under nominally mode I loading, SSDB interfaces remain intact with cyclic crack growth occurring nearly exclusively in the adjacent A1203. In contrast, LPB interfaces fail by the propagation of edge cracks upon exposure to environmental moisture following removal from the bonding chamber.

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 This record is the front matter from a document that appears on a server at MIT and is used through permission from MIT. See http://theses.mit.edu:80/Dienst/UI/2.0/Describe/0018.mit.theses/1999-37 for copyright details and for the full document in image form.

The Influence of Alloy Composition and Interfacial Segregants on the Fracture and Fatigue of Metal/Ceramic Interfaces

by

Frederick G. Gaudette Jr.

Submitted in partial fulfillment of the requirements for the degree of Doctor of Science in Mechanical Engineering

at the Massachusetts Institute of Technology

February 1999
SIGNATURE OF author: [[signature omitted]]

Department of Mechanical Engineering

February 2, 1999

CERTIFIED BY: [[SIGNATURE OMITTED]]

Subra Suresh R.P. Simmons Professor of Materials Science and Engineering Thesis Supervisor Anthony G. Evans
Director of the Princeton Materials Institute, Princeton University Thesis Supervisor ACCEPTED BY: [[SIGNATURE OMITTED]]

Ain A. Sonin

Chairman, Departmental Committee on Graduate Students ARCHIVES MASSACHUSETTS INSTITUTE OF TECHNOLOGY LIBRARIES JUL 12 1999

Massachusetts Institute of Technology Page 1 Dec 31, 1999

Page 2 of 10

The influence of alloy composition and interfacial segregants on the fracture and fatigue of metal/ceramic interfaces

The Influence of Alloy Composition and Interfacial Segregants on the Fracture and Fatigue of MetaliCerainic Interfaces

By Frederick G. Gaudette Jr.

Submitted to the Department of Mechanical Engineering on December 28, 1998, in partial fulfillment of the requirements for the degree of Doctor of Science in Mechanical Engineering

Abstract

The use of multi-layered composites in the aircraft, automotive, and electronics industries is becoming more common as performance requirements exceed the capabilities of homogeneous materials. As a result, the need to assess their failure is critical. Diffusion bonded joints, thermal- barrier and wear resistant coatings, and thin films in VLSI electronics are three examples. In each of these cases, elastic and plastic mismatch between layers, when combined with thermal and/or mechanical loading, results in geometry dependent failure modes.

Through a combination of experimental studies and analytical/numerical modeling, key parameters that affect the fracture and fatigue resistances of metal/ceramic interfaces have been captured. Specifically, results from fracture and fatigue experiments conducted on vacuum diffusion bonded interfaces between A1203 and (i) Ni, (ii) ay-Ni alloy containing Cr and (iii) Al are presented along with numerical simulations of interface fracture in layered materials subjected to a monotonic variation in temperature. The influence of alloy composition, and the interdependence of impurity concentration and bonding state (liquid-phase/solid-state) on interface toughness and fatigue crack growth resistance are discussed, with important findings detailed as follows.

i) Experimental studies designed to characterize the fracture resist...