Effect of alloying with silicon on the damping capacity, physicomechanical properties, and microstructure of quenched alloys in the copper-aluminum system

Abstract

1. A reduction in the number of twins within martensite needles in alloys based on copper and aluminum indicates an increase in thermoelasticity of the martensitic phase and leads to an increase in the level of mechanical vibration energy dissipation at cyclic stress amplitudes close to half the nominal yield point. 2. Alloying of bindary Cu-12.7 wt.% Al alloy with silicon in amounts approximately up to 0.15 wt.%, i.e., up to e/a≅1.52 electrons/atom promotes an increase in martensite needle mobility, and this provides high damping capacity for the alloys over a wide range of cyclic stress amplitude. In this way strength properties are markedly improved, and ductility is reduced a little. 3. An increase in electron concentration for Cu−Al−Si alloys with an increase in the degree of alloying greater than e/a≅1.52 electrons/atom leads to a gradual suppression of martensite transformation and substitution of it by bainite transformation, and also the formation of brittle structural precipitates consisting of γ2 phase located primarily along primary β grain boundaries. As a result of this there is a sharp reduction in both damping and mechanical characteristics of the quenched alloys.