A good strength, high temperature Ni-Al alloy had been produced by thermomechanically cycling sintered aluminium and nickel powders. The microstructure of the alloy consisted of a solid solution in which there was a fine dispersion of inert ceramic particles. A typical micrograph is shown in Fig 1 in which three distinct types of particle A, B and C are indicated. To explain the mechanical properties of the alloy it was necessary to determine the composition and structure of the particles.

As the particles were 300Å to 1200Å in size the only satisfactory method to use was combined electron microscopy and energy analysis. Thinned foils containing unobscured particles were used so that, by placing slit of the Mollenstedt analyser across it, the energy loss spectrum of each particle was measured directly.