Intergranular degradation assessment via random grain boundary network analysis

• US 6,397,682 B2
• Filed: 02/09/2001
• Issued: 06/04/2002
• Est. Priority Date: 02/10/2000
• Status: Expired due to Fees

• Current Assignee: United States Department of Energy
• Original Assignee: United States Of America As Represented By The Department Of Energy
• Inventors: Kumar, Mukul, Schwartz, Adam J., King, Wayne E.
• Primary Examiner(s): NOORI, MAX H
• Application Number:
  US09/780,089
• Publication Number:
  US 20020002865A1
• Time in Patent Office: 480 Days
• Field of Search: 737/60, 737/73, 737/81, 737/88, 738/00, 148/559, 148/668
• US Class Current: 73/760
• CPC Class Codes: G01N 17/00 Investigating resistance of materials to the weather, to corrosion, or to light
• CPC Class Codes: G01N 17/006 of metals

Abstract

A method is disclosed for determining the resistance of polycrystalline materials to intergranular degradation or failure (IGDF), by analyzing the random grain boundary network connectivity (RGBNC) microstructure. Analysis of the disruption of the RGBNC microstructure may be assess the effectiveness of materials processing in increasing IGDF resistance. Comparison of the RGBNC microstructures of materials exposed to extreme operating conditions to unexposed materials may be used to diagnose and predict possible onset of material failure due to

Claims

1. A method of assessing the resistance of a test polycrystalline material to intergranular failure, the method comprising the steps of:

determining the test random grain boundary network connectivity (RGBNC) for said test material;

determining the reference RGBNC for a reference material;

wherein said RGBNC determining steps comprise;

measuring grain boundary misorientations;

categorizing said misorientation as either special or random;

tracking the beginning, end and length of each random boundary (RB) segment along with its connection to adjacent RB segments resulting in a branched network of RB segments;

continuing said tracking step until the network is broken at a point where the RB segment encounters a break point, said break point being a junction comprising a random boundary and at least two other boundaries, wherein said other boundaries are special boundaries, unfavorably oriented random boundaries, or combination of the foregoing;

determining test stereological parameters from said test RGBNC;

determining reference stereological parameters from said reference RGBNC;

wherein said stereologiral parameters are selected from the group consisting of longest interconnected path, mean interconnected path, longest distance from beginning to end of the network, mean distance from beginning to end of network, and radius of gyration of the network; and

comparing said test stereological parameters to said reference stereological parameters.

2. The method as recited in claim 1 wherein:

wherein said misorientations measuring step utilizes electron backscatter diffraction.

3. The method as recited in claim 1 wherein:

said test material has been exposed to at least one extreme operating condition, said condition selected from the group consisting of high temperature, high stress, corrosive environment and combinations of the foregoing.

4. The method as recited in claim 1 wherein:

said test and reference materials are cubic crystalline materials, and said special boundaries have Σ

value ≦

29, and said random boundaries have Σ

value >

29.