Using differential scanning calorimetry to characterize the precipitation hardening phenomena in a Cu-9Ni-6Sn alloy

An attempt has been made to characterize the transformations in a Cu-9Ni-6Sn alloy using heat flux differential scanning calorimetry (DSC) assisted by hardness measurements. Both solution heat treatment and precipitation transformations have been studied. Different starting conditions were imposed on the material to allow a clearer understanding of the transformations involved. The precipitation from the supersaturated solid solution happens in two temperature ranges, i.e., from 200 to 400 degrees C and from 440 to 600 degrees C. In the temperature range from 400 to 440 degrees C, the alloy does not usually transform. Thermal cycles leading to aging and overaging were determined. The precipitation hardening conditions at 350 degrees C or lower for less than 600 min, or 375 degrees C for up to 120 min, lead to metastable precipitation. Precipitation hardening for 120 min at 400 degrees C or 1200 min at 350 degrees C results in stable precipitation and is responsible for overaging the alloy.