Thermodynamics And Concentration Fluctuations Of Liquid Al-Cu And Al-Zn Alloys

Abstract

Thermodynamic properties of liquid Al-Cu and Al-Zn alloys are investigated using the free volume model. We also analyse local atomic arrangements and concentration fluctuations in both liquid binary alloys from the determination of the Warren-Cowley short-range order. For liquid Al-Cu alloys, our findings indicate a strong preference for heteroatomic nearest-neighbors bonds on the Cu-rich side and weaker ones in the Al-rich part while for the liquid Al-Zn alloy, a tendency to the phase separation is observed. Basing on Darken's thermodynamic relationship, diffusivity has been examined for both liquid alloys.Keywords: Al-Cu alloys, Al-Zn alloys, CSRO parameter, free volume model, diffusivity W oparciu o model swobodnej objętości zostały zbadane właściwości termodynamiczne ciekłych stopów Al-Cu i Al-Zn oraz lokalne środowisko atomów w celu obliczenia parametru bliskiego zasięgu Warren-Cowleya. W ciekłych stopach Al-Cu zaobserwowano silną tendencję do tworzenia wiązań hetero-atomowych w obszarze bogatym w Cu, natomiast w obszarze stężeń bogatych w Al znacznie słabszą. W przypadku ciekłych stopów Al-Zn obliczenia wskazują na tendencję do segregacji atomów. Dyfuzja w dyskutowanych stopach została przeanalizowana w oparciu o termodynamiczną definicję podaną przez Darkena.

Structure and chemistry of liquid Al–Cu alloys: molecular dynamics study versus thermodynamics-based modelling

“…Because the S cc (0) function values for Al-Cu liquid alloys are lower than for ideal solution (S cc (0)/S cc (0, id) \ 1), the Al-Cu alloys rather have a tendency for compound formation according to the definition given by Bhatia and Thornton [47]. In turn, the present CFM-Al 2 Cu and MEAM-MD simulation results are in line with this observation and FVM computation data [23] over the whole range of Cu concentrations investigated, as opposed to the selected ones found by our present CFM-Al 2 Cu 3 calculation.…”

“…The ''associate forming tendency'' has been partially studied by Trybula et al [23], using the free volume model (FVM), but this investigation provided only fragmentary insights into the structure and thermodynamics of Al-Cu liquid alloys. Unfortunately, those results were not enough to fully describe the physical phenomena occurring in the liquid state of the Al-Cu alloys due to the FVM constraints [24].…”

Structure and transport properties of the liquid Al80Cu20 alloy – A molecular dynamics study

“…Understanding these properties is an essential step in processing of polycrystalline or amorphous materials, which are of great technological importance and scientific interest, for designing modern high performance engineering and functional materials like metallic glasses (MGs) [1] or investigation of the liquid-solid phase transformation [2]. In this particular case, knowledge of the interplay between the structural and transport properties such as diffusion and viscosity of a melt is vital to understand the physical phenomena occurring in the liquid phase [3,4].…”

“…In recent years, molecular dynamics simulations have gained particular attention in the investigation of bulk materials' properties [4,5] and are becoming efficient enough to predict the properties of real materials [6,7]. However, a major problem is to exactly describe the interatomic interactions, in practise, they are parametrized using mathematical models of semi-empirical potentials [8].…”

“…The analysed Al-Cu alloys are characterised by low density and good mechanical strength in comparison to the conventional Al alloys. Apart from the aforementioned studies, significantly less theoretical contributions, concerning the liquid Al-Cu alloys, were reported in the literature [24][25][26]. Basically, two Al-Cu compositions gained considerable interest, these are the eutectic Al 83 Cu 17 (or Al 80 Cu 20 ) and Al 60 Cu 40 alloys.…”