Microstructures
by George Langford, Sc.D., Massachusetts Institute of Technology, Cambridge, MA, 1966
Copyright©2005 by George Langford
Non Ferrous Alloys - Lesson 3 - First specimen
Cast aluminum bronze at 500X potassium chromate etch
 This is a cast aluminum bronze, shown here at 500X magnification.  The etchant was an aqueous solution of potassium chromate (K2Cr2O7).

How many microconstituents can you identify ?




From left to right, there's the Pacific Ocean, then Baja California & the gulf coast, oil rigs in the Gulf of Mexico, Florida, and the southeastern USA.  Not shown: Bermuda ... just kidding ... I made this image 43 years ago and only just now noticed the resemblance ...
Copper-aluminum system


It may help to refer to the copper - aluminum phase diagram sketched at left.









For the answer, click here.













At least four !  There are islands of alpha in a beta matrix, peritectic gamma-1 (the last areas to freeze) and a precipitate of gamma-2 in the beta phase.                                             Proceed to Specimen 2.