Irradiation-induced void evolution in iron：A phase-field approach with atomistic derived parameters

A series of material parameters are derived from atomistic simulations and implemented into a phase field（PF） model to simulate void evolution in body-centered cubic（bcc） iron subjected to different irradiation doses at different temperatures.The simulation results show good agreement with experimental observations — the porosity as a function of temperature varies in a bell-shaped manner and the void density monotonically decreases with increasing temperatures; both porosity and void density increase with increasing irradiation dose at the same temperature. Analysis reveals that the evolution of void number and size is determined by the interplay among the production, diffusion and recombination of vacancy and interstitial.

Nanoparticles Deposition at Specific Sites Using Aligned Fiber Networks

We report a new method to precisely locate inorganic nanoparticles at polymeric fiber crossing sites. Polymeric fibers are aligned by a previously reported non-electrospinning Spinneret based Tunable Engineered Parameters (STEP) polymeric fiber manufac- turing technique. Cross-hatch pattern (perpendicular) of polymeric fibers embedded with inorganic nanoparticles (e.g.: Fe(NO3)3 or Bi(NO3)3) were fabricated on top of each other and the fiber compositions re-acted during annealing process, thus, producing a desired phase (e.g.: BiFeO3) only at the crossing site. Our method of-fers an easy way to mass arrange and locate nanoparticles at designed positions on virtually all types of substrates.

Resolution of a discrepancy of magnetic mechanism for Elinvar anomaly in Fe-Ni based alloys

Fe-Ni based Elinvar alloys performing temperature-independent elastic modulus over a wide temperature range have found wide and significant applications. Although numerous models involved with magnetism have been proposed to explain the Elinvar anomaly, some of the puzzles concerning the anomaly have not been fully understood. In this work, a remarkable discrepancy between the inflection temperature of modulus and the Curie temperature in a typical Fe-Ni-Cr Elinvar alloy was found,challenging the magnetic mechanism for Elinvar anomaly. Microstructural characterization and dynamic mechanical analysis demonstrate the occurrence of a strain glass transition with continuous formation of nanodomains. Accompanying such a transition, the gradual softening in the elastic modulus of austenite offsets the modulus hardening due to the vibrational anharmonicity of nanodomains upon cooling, leading to the Elinvar effect. As a result, the inflection temperature of modulus corresponds to the initiation of nanodomains' formation instead of magnetic transition. Our findings specify the association of Elinvar anomaly with structural aspects, and provide new insights into the mechanism of Elinvar anomaly in Fe-Ni based alloy.

Ferroic glasses

Ferroic glasses(strain glass,relaxor and cluster spin glass)refer to frozen disordered states in ferroic systems;they are conjugate states to the long-range ordered ferroic states—the ferroic crystals.Ferroic glasses exhibit unusual properties that are absent in ferroic crystals,such as slim hysteresis and gradual property changes over a wide temperature range.In addition to ferroic glasses and ferroic crystals,a third ferroic state,a glass-ferroic(i.e.,a composite of ferroic glass and ferroic crystal),can be produced by the crystallization transition of ferroic glasses.It can have a superior property not possessed by its two components.These three classes of ferroic materials(ferroic crystal,ferroic glass and glass-ferroic)correspond to three transitions(ferroic phase transition,ferroic glass transition and crystallization transition of ferroic glass,respectively),as demonstrated in a generic temperature vs.defectconcentration phase diagram.Moreover,through constructing a phase field model,the microstructure evolution of three transitions and the phase diagram can be reproduced,which reveals the important role of point defects in the formation of ferroic glass and glass-ferroic.The phase diagram can be used to design various ferroic glasses and glass-ferroics that may exhibit unusual properties.