Étude des alliages binaires Cu-Ag, Cu-Sb et Cu-In et de l’effet de l’addition du bismuth

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.