DSC evaluations in quenched and in cold-rolled Cu-20 at.% Mn alloys

Abstract

Calorimetric energy measurements associated with the different peaks involved during the linear heating of Cu-20 at.% Mn were performed employing cold-rolled and quenched materials. Unlike the situation in the quenched alloy in which disperse-short-range order (DSRO) is developed, in the deformed alloy such a process is inhibited by the segregation of solute atoms to partial dislocations. This conclusion was drawn by determining the dislocation density in the deformed alloy on the basis of expressions governing the energy release which accompanies the pinning process. After the computed value for the dislocation density had been employed to evaluate the energy evolved during recrystallization, it is verified that this energy does not differ much from the experimentally measured value. The above interpretation of the behaviour exhibited by this alloy is also supported by kinetics and solute balance analyses. After tensile tests performed in the deformed alloy subjected to a low thermal heat treatment at 423 K for 30 min, an increase in 0.2 offset YS (yield stress) of 25 and 21% in UTS (ultimate tensile strength) was achieved, if compared with those values corresponding to the deformed alloy without heat treatment. However, the as quenched alloy subsequently heat treated at 560 K for 30 min exhibits an increase of 10% in 0.2% offset YS, and a very small increment in UTS with respect to the solely quenched alloy condition.