Abstract
A transmission electron microscope study has been made on the structure of beta phase in quenched Cu-14.80 at% Sn alloy, and also on the structure of its decomposition products by tempering. Firstly it has been confirmed that the decomposition products are α-and δ-phases. Their orientation relationships are (111)x⁄⁄(110)δ, [10\bar1]⁄⁄[1\bar11]δ, the principal axes of δ coinciding with those of the matrix beta phase. The η-phase seems to precipitate on tempering at comparatively low temperatures. As for the matrix in the quenched alloy, its electron micrograph has a mottled structure in most cases. The electron diffraction pattern of such a structure has diffraction spots of α-, δ-, or η-phase besides those of the retained beta phase (called β2). It seems therefore that the retained phase obtained by quenching is partly tempered by beam heating in the electron microscope. The structure of the retained phase untempered is basically of the Fe3Al type, but it has a long period which is 3 times as large as the (110) spacing of the latter. This period has tentatively been interpreted by a model which is formed from the Fe3Al type lattice (β1) by substituting Cu atoms for Sn atoms lying on every third (100) layer.
