First Principle Calculation Of Generalized Planar Fault Energy In Al-Na Alloys And Al-Si Alloys

Mechanical properties of the nanocrystals can be significantly improved through thecreation of artificial defects. And the dislocation slip and twinning are two predominantmechanisms in nano-crystalline deformation. and determine the toughness, the brittle, thestrength and other macro-phenomenon about materials. Related research takes more andmore attention of people’s. It is a hotspot topic in condensed matter physics and materialscience.In order to understand the effect of various concentrations and different impurities onslip and twinning, and to seek the explanation at the micro level, the generalized planestacking fault energy of metal Al with the high stacking-fault energy, Al-Na alloy withsolute concentration of 3.85 at.% and 5.77 at.% and Al-Si alloy have been accuratelycalculated, which are based on first principle of density functional theory. The criticaltwinning stresses for twin deformation have been predicted based on Kibey presentmodels and theories. It shows that Intrinsic stable stacking fault energy and entiregeneralized planar fault-energy decrease when adding impurities as Na or Si to pure Aland the critical twinning stress also decreases, which makes the pure Al more easytwinning in the case of doping Na or Si. We also use the analysis method of charge densityand density of states to research stability stacking fault, and reveals the interactionbetween the atoms of key positions in the twin process from electronic level. The resultsshow that the intervention of the atoms of Na and Si has effect on charge distribution ongrain boundary and the change of the chemical bonds between atoms has impact on GPFE.It further expounds the reasons of the decrease of critical twinning stress of twin in alloyand the increase of twin tendency.The research of the GPFE of Al and Al alloy and the explanation of the change ofGPFE from electronic level can reveal the deformation mechanism of nano-crystalline,which improves the mechanical properties of nano-crystalline. Based on these discussions,the paper gives the theoretical basis of the twin mechanisms of nano-alloy materials intheorys. And contact with the macroscopic phase. At the same time, the result of this paperplayed an important in guiding significance on the alloy design.