Yoshitsugu Amano

Mechanism of Precipitation of α from β in 60:40 Brass

Body-centred cubic β brass, containing ca. 40% Zn, obtained by quenching from 850°∼900°C. shows reversal process of Kurdjumow and Sachs type transformation during tempering. Various intermediate structures between β and face-centred cubic α were ascertained by means of X-ray analysis using capillary and ordinary X-ray tubes. Such are body-centred and face-centred tetragonal structures having various axial ratios; therefore the transformation must take, place with gradual manner, although the formation of martenstic needles are well known. The decrease of solubility of Zn in a solid solution due to lowering of the temperature, determined from X-ray data, is more significant than of Konobejewski.

Effect of grain boundary migration in solution treatment on grain boundary precipitation of Al-Fe dilute alloys

Grain boundary internal friction in the Al-0.002 wt.% Fe alloy was measured to examine an interaction between moving boundaries and solute atoms. When both the alloys solution treated for a short time at 773K in which grains are growing and solution treated for a prolonged time in which grain growth has been ceased are subsequently aged at 593K, grain boundary precipitation occurs within a shorter time in the former. This fact is in consistent with the assumption that greater quantities of solute atoms segregate in moving boundaries than in stationary boundaries. If the alloy is solution treated at elevated temperatures above 823K, however, longer times are required for grain boundary precipitation when grains are growing in the solution treatment. This may be due to the breaking away of the moving boundary from the solute atmosphere.