Microstructures
by George Langford, Sc.D., Massachusetts Institute of Technology, Cambridge, MA, 1966
Copyright©2005 by George Langford
Unknowns, Non-Ferrous - Set 2 - Sixth specimen - M.I.T.'s #303
50%Cu, 30%Zn, 10%Fe, 5%Ni, & 2%Sn at 50X etched
 The X-ray fluorescence analysis that one of the students in my class obtained from this specimen showed the following composition: 50%Cu, 30%Zn, 10%Fe, 5%Ni, & 2%Sn.  The percentages are crude approximations, as there are many corrections that have to be applied to the intensities of the characteristic X-ray wavelengths to account for absorption and re-emission of gamma rays by the different elements when they are all present together in the one specimen.

The hardness of the primary (white) phase was Rockwell C57; overall hardness was Rockwell C28.  These are quite high for a non ferrous metal.

My magnifications are: 50X; 200X; 500X; and 1000X.
50%Cu, 30%Zn, 10%Fe, 5%Ni, & 2%Sn at 200X etched
 The microstructure shows only two phases, one white and very hard, the other a dazzling lemon yellow and considerably softer.
50%Cu, 30%Zn, 10%Fe, 5%Ni, & 2%Sn at 500X etched
 Here you can just barely see a few grain boundaries in the white phase.

There wasn't much any of us could say about this one, but you're free to speculate ... and I'll cheerfully discuss it with you.  All I can say is that there are two kinds of non-sparking alloys that are used for tools in flammable environments.  One is berryllium copper (which was already discussed in an earlier lesson) and the other is aluminum bronze.  But there's no aluminum here. Neither alloy has appreciable zinc, nickel, or iron.  Hint: Look at the copper - iron and copper - nickel phase diagrams.  Remember: The yellow phase isn't the hard one.  It's just holding the white stuff together.
50%Cu, 30%Zn, 10%Fe, 5%Ni, & 2%Sn at 1000X etched
 Homer Simpson on a small scale ...

Write out your answer; complete all or part of the set; and then apply for a Username & Password so you can activate the link at the bottom of this page.
Go on to your analysis of Specimen 7.


























Answer: Follow this link.