Alloys of Cu–15at.% Al, Ag–21at.% Zn and Au–14at.% Fe are compared with respect to short-range ordering in the recrystallized state and after high deformation by cold-rolling, respectively. Additional information on the defect annealing behaviour is gained from an investigation of microhardness and by microscopy.

Microhardness of stoichiometric CuAu was measured during isochronal hearing starting from the disordered and the ordered state as well as for isochronal cooling from the disordered state. It is shown that a continuous increase of long-range order connected with similar hardness behaviour was observed in all cases of thermal treatment and pre-treatment. In correspondence with earlier resistometric experiments during isochronal temperature variation no hysteresis between heating and cooling was observed.

It is well investigated that concentrated {alpha}-CuAl shows effects of short-range order (SRO) which for thermodynamical reasons are a function of temperature. In most cases, however, it was tried rather to carefully avoid complications by a defect structure than to study SRO-effects in the presence of a heavily defected microstructure after plastic deformation. Depending on the temperature ranges of recovery and recrystallization, defect annihilation of a cold-worked alloy may occur simultaneously with changes in the degree of SRO during an annealing treatment. In previous works on {alpha}-AgZn it has been shown that these processes of defect recovery and SRO could be separated. For the technical application of a material, but also as a basis for the separation of SRO-effects from effects of defect annealing it is of great interest to investigate the microstructural changes during post-deformation annealing. In a preliminary study on the interaction between SRO and post-deformation annealing certain stages of defect annealing could be detected. In the present work the authors concentrate on the interpretation of the microstructure of these stages as studied by TEM.

Short-range ordering (SRO) kinetics was investigated in plastically deformed and recrystallized alpha-CuAl by means of electrical resistivity and microhardness measurements during isochronal annealing. The results are compared with previous ones on alpha-AgZn and alpha-AuFe [1,2,3]. Under certain assumptions changes of resistivity due to changes of SRO only, can be separated from changes caused by defect recovery which occur simultaneously during annealing in the deformed state. Isothermal resistivity measurements in the recrystallized state yield information on the processes of ordering kinetics. Fitting a simple model for SRO relaxation to the pure SRO-induced resistivity changes, material parameters like migration and formation enthalpies of vacancies and dislocation density can be obtained.

A study of post-deformation annealing was made on Cu-15at.%Al cold-rolled to about 60% reduction in thickness. Starting from results as measured by electrical resistivity, changes of simultaneous defect recovery and short-range ordering (SRO) were compared with microhardness measurements. It is shown that changes of SRO can be carefully separated from simultaneously occurring processes of defect recovery. Further, SRO-kinetics in the deformed state is compared with that of completely recrystallized state.

Differential scanning calorimetry (DSC) and microhardness measurements were used to study the kinetics of L1(0)-ordering in CuAu. During dynamic heating a decrease of order/disorder transition temperature T-O/D was observed with increasing heating rate. This is just opposite to what one would expect for a first order phase transition usually yielding an effect of superheating. It is shown that this 'retro'-effect is caused by a shift of T-O/D to lower temperatures during heating which was initiated during previous cooling cycle. The origin appears to be the stabilisation of CuAuI ordered phase against complete transformation into CuAuII during heating by twinning and loss of coherency of ordered domains during previous cooling cycle.

The effect of heating and cooling on the long-range order transformation in stoichiometric CuAu is investigated by several complementary measuring methods. Measurements of heat flow, resistometry and acoustic emission are done dynamically by linear heating/cooling. It is shown that measuring dynamically yields the expected effect of undercooling, which decreases with decreasing cooling rate. The dependence of undercooling on cooling rate is compared with the concept of continuous cooling for glass forming. A small influence of heating rate on disordering temperature is reported (retro-effect).