Abstract:
The aim of this work is the study of Cu-Ag, Cu-In and Cu-Sb binary alloys and the effect of the bismuth
addition (30 ppm, 120 ppm and 0.5%at) on the discontinuous precipitation reaction and the microstructure recovery
after plastic deformation by using mainly anisothermal analyzes using various heating rates to study the reaction
kinetics in each alloy. For that several experimental methods were used: dilatometry, optical microscopy, X-ray
diffraction, transmission and scanning electron microscopy (TEM, SEM), differential scanning calorimetry (DSC),
and microhardness measurements.
The dilatometric and calometric analyzes permit to follow and classify the precipitation and dissolution
kinetics in these alloys and to calculate the activation energy of each reaction. The variation of the dissolution
activation energy is quite related to the precipitated phase stability and available chemical component of the driving
force. The bismuth addition hasn’t an important effect on the precipitation product morphology and the dissolution
kinetics.
The obtained results confirm the important influence of the plastic deformation on the dilatometric
behaviours. Our investigation is essentially axed on contribution of the x-rays diffraction lines profile analysis in the
explanation of the dilatometric behaviour of these alloys by means of the microstructural parameters and their
evolution during heating. These results were completed by DSC analyses, TEM and SEM observations. The
obtained results are summarized below:
· the chemical force predominance in the high supersaturation alloy induces slow microdistorsions reduction and
low crystallites growth and favors the cellular precipitation. In the contrary case, the microdistorsions relaxation
is achieved simultaneously with the primary recrystallization which competes with precipitation.
· the alloys having segregation at grains boundaries present an important contraction during the grains growth. If
the electrons concentration is weak the stored interfacial energy, after primary recrystallization, is important,
· the bismuth particles dispersed in the matrix play the role of the second phase dispersed particles, accelerate the
recrystallization and give an important dilatometric effect related to the increase of the copper solubility in the
liquid bismuth,
· if the precipitates are a solid solution, the dissolution process is accompanied by the solute permutation between
the two solid solutions.
· the indication of the recrystallization progression from (220) and (111) peaks intensities evolution depends on
the alloy plasticity.
