Abstract
The isothermal decomposition products of hot worked beta and sigma copper tin alloys have been studied after varying times at different annealing temperatures. Electrical resistivity temperature curves have been measured on heating the hot worked alloy through the beta and sigma regions, as has the effect of annealing in these regions on the as quenched electrical resistivity. The crystal structures of the phases observed have been examined temperature, briefly, and on quenching to room temperature. The effect of small additions of nickel on the beta and sigma phase has been examined using identical techniques to those applied to the binary alloys. it has been shown that the decomposition products of the 26% and 27% tin alloys depends, after hot working, on the annealing time at temperature and that the change in decomposition products can be correlated with the beta to sigma transformation and ordering of the beta phase. Changes observed in the electrical resistivity of the beta and sigma phases can be correlated with the effects observed during isothermal transformation but the resistivity of the phases retained by quenching is difficult to interpret due to the complicating factors of martensite formtion and possibly vacancy retention. The structure of the beta phase retained by quenching has been shown to have an ordered body centred cubic structure associated with varying amounts of martensite. The addition of nickel results in the formation of a two phase (beta + sigma) region not observed in the binary alloys, but otherwise similar effects are found. A modified binary copper tin has been suggested in the light of the results obtained.