Ordering in liquid and its heredity impact on phase transformation of Mg-Al-Ca alloys

It is a long-sought goal to achieve desired mechanical properties through tailoring phase formation in alloys,especially for complicated multi-phase alloys.In fact,unveiling nucleation of competitive crystalline phases during solidification hinges on the nature of liquid.Here we employ ab initio molecular dynamics simulations(AIMD)to reveal liquid configuration of the Mg-Al-Ca alloys and explore its effect on the transformation of Ca-containing Laves phase from Al2Ca to Mg_(2)Ca with increasing Ca/Al ratio(rCa/Al).There is structural similarity between liquid and crystalline phase in terms of the local arrangement environment,and the connection schemes of polyhedras.The forming signature of Mg_(2)Ca,as hinted by the topological and chemical short-range order originating from liquid,ascends monotonically with increasing rCa/Al.However,Al_(2)Ca crystal-like order increase at first and then decrease at the crossover of rCa/Al=0.74,corresponding to experimental composition of phase transition from Al_(2)Ca to Mg_(2)Ca.The origin of phase transformation across different compositions lies in the dense packing of atomic configurations and preferential bonding of chemical species in both liquid and solid.The present finding provides a feasible scenario for manipulating phase formation to achieve high performance alloys by tailoring the crystal-like order in liquid.

DID Code:A Bridge Connecting the Materials Genome Engineering Database w让h Inheritable Integrated Intelligent Manufacturing

A data identifier(DID)is an essential tag or label in all kinds of databases—particularly those related to integrated computational materials engineering(ICME),inheritable integrated intelligent manufacturing(I3M),and the Industrial Internet ofThings.With the guidance and quick acceleration of the developme nt of advanced materials,as envisioned by official documents worldwide,more investigations are required to construct relative numerical standards for material informatics.This work proposes a universal DID format consisting of a set of build chains,which aligns with the classical form of identifier in both international and national standards,such as ISO/IEC 29168-1:2000,GB/T 27766-2011,GA/T 543.2-2011,GM/T 0006-2012,GJB 7365-2011,SL 325-2014,SL 607-201&WS 363.2-2011,and QX/T 39-2005.Each build chain is made up of capital letters and numbers,with no symbols.Moreover,the total length of each build chain is not restricted,which follows the formation of the Universal Coded Character Set in the international standard of ISO/IEC 10646.Based on these rules,the proposed DID is flexible and convenient for extendi ng and sharing in and between various cloud-based platforms.Accordingly,classical two-dimensional(2D)codes,including the Hanxin Code,Lots Perception Matrix(LP)Code,Quick Response(Q.R)code,Grid Matrix(GM)code,and Data Matrix(DM)Code,can be constructed and precisely recognized and/or decoded by either smart phones or specific machines.By utilizing these 2D codes as the fingerprints of a set of data linked with cloud-based platforms,progress and updates in the composition-processing-structure-property-performance workflow process can be tracked spontaneously,paving a path to accelerate the discovery and manufacture of advanced materials and enhance research productivity,performance,and collaboration.

View and Comments on the Data Ecosystem:"Ocean of Data"

In a recent paper[1],I discussed the concept of the"ocean of data,"in a response to ever-increasing computing power and large numbers of online data repositories.These settings call for a new paradigm of computational framework that connects various data repositories,incorporates machine learning,reuses existing data,and guides new computation and experimental efforts to create a"sustainable ecosystem"of data and tools.

Electronic structures and strengthening mechanisms of superhard high-entropy diborides

High-entropy diborides(HEBs)have attracted extensive research due to their potential ultra-high hardness.In the present work,the effects of transition metals(TM)on lattice parameters,electron work function(EWF),bonding charge density,and hardness of HEBs are comprehensively investigated by the first-principles calculations,including(TiZrHfNbTa)B_(2),(TiZrHfNbMo)B_(2),(TiZrHfTaMo)B_(2),(TiZrNbTaMo)B_(2),and(TiHfNbTaMo)B_(2).It is revealed that the disordered TM atoms result in a severe local lattice distortion and the formation of weak spots.In view of bonding charge density,it is understood that the degree of electron contribution of TM atoms directly affects the bonding strength of the metallic layer,contributing to the optimized hardness of HEBs.Moreover,the proposed power-law-scaled relationship integrating the EWF and the grain size yields an excellent agreement between our predicted results and those reported experimental ones.It is found that the HEBs exhibit relatively high hardness which is higher than those of single transition metal diborides.In particular,the hardness of(TiZrNbTaMo)B_(2)and(TiHfNbTaMo)B_(2)can be as high as29.15 and 28.02 GPa,respectively.This work provides a rapid strategy to discover/design advanced HEBs efficiently,supported by the coupling hardening mechanisms of solid solution and grain refinement based on the atomic and electronic interactions.

Atomic and electronic basis for the serrations of refractory high-entropy alloys

Refractory high-entropy alloys present attractive mechanical properties,i.e.,high yield strength and fracture toughness,making them potential candidates for structural applications.Understandings of atomic and electronic interactions are important to reveal the origins for the formation of high-entropy alloys and their structure−dominated mechanical properties,thus enabling the development of a predictive approach for rapidly designing advanced materials.Here,we report the atomic and electronic basis for the valence−electron-concentration-categorized principles and the observed serration behavior in high-entropy alloys and highentropy metallic glass,including MoNbTaW,MoNbVW,MoTaVW,HfNbTiZr,and Vitreloy-1 MG(Zr_(41)Ti_(14)Cu_(12.5)Ni_(10)Be_(22.5)).We find that the yield strengths of high-entropy alloys and high-entropy metallic glass are a power-law function of the electron-work function,which is dominated by local atomic arrangements.Further,a reliance on the bonding-charge density provides a groundbreaking insight into the nature of loosely bonded spots in materials.The presence of strongly bonded clusters and weakly bonded glue atoms imply a serrated deformation of high-entropy alloys,resulting in intermittent avalanches of defects movement.

First-principles calculations of lattice dynamics and thermal properties of polar solids

Although the theory of lattice dynamics was established six decades ago,its accurate implementation for polar solids using the direct(or supercell,small displacement,frozen phonon)approach within the framework of density-function-theory-based first-principles calculations had been a challenge until recently.It arises from the fact that the vibration-induced polarization breaks the lattice periodicity,whereas periodic boundary conditions are required by typical first-principles calculations,leading to an artificial macroscopic electric field.The article reviews a mixed-space approach to treating the interactions between lattice vibration and polarization,its applications to accurately predicting the phonon and associated thermal properties,and its implementations in a number of existing phonon codes.

High-throughput investigations of configurational-transformation-dominated serrations in CuZr/Cu nanolaminates

Metallic amorphous/crystalline(A/C)nanolaminates exhibit excellent ductility while retaining their high strength.However,the underlying physical mechanisms and the resultant structural changes during plastic deformation still remain unclear.In the present work,the structure-property relationship of CuZr/Cu A/C nanolaminates is established through integrated high-throughput micro-compression tests and molecular dynamics simulations together with high-resolution transmission electron microcopy.The serrated flow of nanolaminates results from the formation of hexagonal-close-packed(HCP)-type stacking faults and twins inside the face-centered-cubic(FCC)Cu nano-grains,the body-centered-cubic(BCC)-type ordering at their grain boundaries,and the crystallization of the amorphous CuZr layers.The serration behavior of CuZr/Cu A/C nanolaminates is determined by several factors,including the formation of dense dislocation networks from the multiplication of initial dislocations that formed after yielding,weak-spots-related configurational-transitions and shear-transition-zone activities,and deformation-induced devitrification.The present work provides an insight into the heterogeneous deformation mechanism of A/C nanolaminates at the atomic scale,and mechanistic base for the microstructural design of self-toughening metallic-glass(MG)-based composites and A/C nanolaminates.

Searching for a route to synthesize in situ epitaxial Pr_(2)Ir_(2)O_(7) thin films with thermodynamic methods

In situ growth of pyrochlore iridate thin films has been a long-standing challenge due to the low reactivity of Ir at low temperatures and the vaporization of volatile gas species such as IrO_(3)(g)and IrO_(2)(g)at high temperatures and high PO_(2).To address this challenge,we combine thermodynamic analysis of the Pr-Ir-O_(2)system with experimental results from the conventional physical vapor deposition(PVD)technique of co-sputtering.Our results indicate that only high growth temperatures yield films with crystallinity sufficient for utilizing and tailoring the desired topological electronic properties and the in situ synthesis of Pr_(2)Ir_(2)O_(7)thin films is fettered by the inability to grow with PO_(2)on the order of 10 Torr at high temperatures,a limitation inherent to the PVD process.Thus,we suggest techniques capable of supplying high partial pressure of key species during deposition,in particular chemical vapor deposition(CVD),as a route to synthesis of Pr_(2)Ir_(2)O_(7).