title: Composition- and temperature-dependent liquid structures in Al-Cu alloys: an ab initio molecular dynamics and x-ray diffraction study.
abstract: The composition- and temperature-dependent liquid structures in eight Alrich-Cu binary alloys (from hypoeutectic Al93Cu7to hypereutectic Al70Cu30) have been experimentally and computationally studied by x-ray diffraction (XRD) experiments and ab initio molecular dynamics (AIMD) simulations. The remarkable agreements of structure factors for all liquid Alrich-Cu alloys obtained from high-temperature high-energy XRD measurements and AIMD simulations have been achieved, which consolidates the analyses of structural evolutions in Alrich-Cu liquids during the cooling processing by AIMD simulations. The heat capacity of liquid Alrich-Cu alloys continuously increases and presents no abnormal peak when reducing the temperature, which differs from the reported prediction for 55-atom Alrich-Cu nanoliquids. The diffusivities of Al and Cu undergo an increasing deviation from Arrhenius behavior by tuning Cu concentration from 7 to 30 atomic percentages, correlated to the local ordering in these liquids by means of coordination number, bond-angle distribution, Honeycutt-Andersen index, bond-orientational order and Voronoi tessellation analyses. Upon cooling, the microstructure of the liquid Alrich-Cu alloys inclines to form Al2Cu crystal-like local atomic ordering, especially in the hypereutectic liquids. The favorable short-range ordering between Cu and Al atoms could cause the non-Arrhenius diffusion behavior.
authors.affiliation: International Center for New-Structured Materials (ICNSM), Laboratory of New-Structured Materials, State Key Laboratory of Silicon Materials, and School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China.
authors.forename: L H
authors.initials: LH
authors.lastname: Xiong
authors.forename: X D
authors.initials: XD
authors.lastname: Wang
authors.forename: Q P
authors.initials: QP
authors.lastname: Cao
authors.forename: D X
authors.initials: DX
authors.lastname: Zhang
authors.forename: H L
authors.initials: HL
authors.lastname: Xie
authors.forename: T Q
authors.initials: TQ
authors.lastname: Xiao
authors.forename: J Z
authors.initials: JZ
authors.lastname: Jiang