Direct evidence for competition between metastable ω and equilibrium α phases in aged β-type Ti alloys

Precipitation response of a recently developed β-type Ti-25Nb-2Mo-4Sn alloy （wt%） during aging was investigated in detail. Experimental results indicate that the metastable co or equilibrium α phase can form alternatively even under the same aging condition, depending on the condition prior to the aging, i.e., solution treatment or severe cold rolling. This provides, for the first time, the direct evidence for the competition between ω and α in aged β-type Ti alloys. This peculiar aging response is found to be closely related to high-density dislocations and grain boundaries which suppress the formation of ω but favor the precipitation of fine α phase.

Interfacial phase competition induced Kondo-like effect inmanganite-insulator composites

A Kondo-like effect, namely, the upturn of resistivity at low temperatures, is observed in perovskite manganite when nonmagnetic insulators are doped as secondary phase. In this paper, the low-temperature resistivity upturn effect has been argued to originate from interfacial magnetic phase reconstruction. Heisenberg spin lattices have been simulated using the Monte Carlo method to reveal phase competition around secondary phase boundary, namely, manganite-insulator boundary that behaves with a weak antiferromagnetic tendency. Moreover, the resistor network model based on double-exchange conductive mechanism reproduces the low-temperature resistivity upturn effect. Our work provides a reasonable physical mechanism to understand the novel transport behaviors in microstructures of correlated electron systems.

Simulation of the magnetoresistance of Heisenberg spin lattices using the resistor network model

The magnetism and conductance of two-dimensional Heisenberg spin lattices are investigated by using Monte Carlo simulations to qualitatively understand a fascinating magnetoresistance effect observed in magnetic materials and their artificial multilayers. Various magnetic profiles, including a pure ferromagnetic, a pure antiferromagnetic, two phase com-petitive cases, and an artificial sandwich junction, are simulated, and their conductances are calculated based on an extended resistor-network model. Magnetoresistance is observed in some lattices, which is prominent when the system is near phase boundaries. Compared with real manganites, the absence of colossal magnetoresistance in our simulation implies the es- sential role of charge ordered phase which is not included in our pure spin model. However, our model provides an intuitive understanding of the spin-dependent conductance in large scale.

Deterministic Dual Control of Phase Competition in Strained BiFeO_(3):A Multiparametric Structural Lithography Approach

The realization of a mixed-phase microstructure in strained BiFeO_(3)(BFO)thin films has led to numerous novel effects derived from the coexistence of the tetragonal-like monoclinic phase(T phase)and rhombohedral-like monoclinic phase(R phase).Strong strain and polarization diiferences between the phases should result in a high level of transformation plasticity,which enables the continuous alteration of the relative proportion of R and T states in response to external forces.Although the potential for utilizing such plasticity to control mixed-phase populations under external stimuli is evident,direct experi・mental evidence backed by equilibrium predictions has not yet been fully demonstrated.Here we demonstrate deterministic control of mixed-phase populations in an epitaxially strained BFO thin film through the application of localized stresses and electric fields in a reversible manne匚The results illustrate and rationalize deterministic control of mixed phases in strained BFO films,which could be crucial in tuning their functional properties.The findings also highlight a new multiparametric technique in the scanning probe lithography toolbox based on tip-assisted electric and strain field manipulation of functional properties that might find application beyond the ferroelectric domain and structural phase lithography.

Distribution of α-, β-, and γ-Phases in a Multi-flow Injection-molded Hierarchical Structure

In the current work, a custom-made vibration injection molding device that can provide oscillatory pressure was utilized to create an injection-molded hierarchical structure. Growth competition among α, β, and γ phases in the injection-molded structure can be studied because of the presence of this hierarchical structure, wherein shish-kebab and spherulite layers were arranged alternately along the thickness direction. The γ crystals only existed in layers subjected to high pressure and shear stress, whereas β crystals formed between the shear layers. The change in trend of the γ fraction was similar to that of parent-to-daughter ratio. In addition, this hierarchical and alternating crystal structure can sharply increase the mechanical properties.