Microstructures
by George Langford, Sc.D., Massachusetts Institute of Technology, Cambridge, MA, 1966
Copyright©2005 by George Langford
Non Ferrous Alloys - Lesson 3 - Ninth specimen
Oilite bronze bearing at 100X
 Here is a porous bronze "Oilite" bearing, made from elemental powders of copper, tin, and graphite. 

The first photomicrograph was taken at 100X, the second one at 500X.  The etchant was ammonium hydroxide - hydrogen peroxide.
Oilite bronze bearing at 500X
 What heat treatment has it had ?






Look carefully at the photomicrographs, especially the second one, before looking at the answer below.










The sintering temperature was too low to produce adequate diffusional homogenization, as evidenced by the pink copper particles still remaining in the 1000X photomicrograph.  The copper particles are even still fine grained !
 Now look at Specimen 10.