1. a Department of Metallurgy and the Materials Research Laboratory , University of Illinois , 1304 W. Green Street, Urbana , Illinois , 61801 , U.S.A.
2. b Metallurgy Division , National Bureau of Standards , Gaithersburg , Maryland , 20899 , USA
3. c United Technologies Research Center , Silver Lane, East Hartford , Connecticut , 06108 , U.S.A.