Extensive experiments have shown that the transformation from the face-centered cubic to hexagonal close-packed ε phase usually occurs around coherent Σ3 boundaries. However, in this letter, we reveal a different transformation mechanism in a metastable dual-phase compositionally complex alloy via a systematic high-resolution scanning transmission electron microscopy analysis. The face-centered cubic γ matrix can be transformed to the hexagonal close-packed ɛ phase (as small as one unit) around an incoherent Σ3 boundary (~30 nm), i.e., the facet of the coherent Σ3 boundary. This transformation is assisted by the detwinning/twin growth of a coherent Σ3 boundary during annealing treatment (900 °C for 60 min).

Materials with tunable negative thermal expansion (NTE) are highly demanded in various functional devices. La(Fe, Si)₁₃-based compounds are promising NTE materials due to their outstanding NTE properties. However, their poor mechanical properties and related short service life restrict their practical applications. In this work, epoxy resin with positive thermal expansion is used to synthesize La-Fe-Si/resin composites. The NTE of La-Fe-Si/resin composites can be manipulated by optimizing the La-Fe-Si particle size and resin content, and tailoring resin content could tune the NTE more effectively. The average linear coefficient of thermal expansion of the composites decreases from -275.0 × 10^-6 K^-1 to -4.9 × 10^-6 K^-1 over the magnetic transition temperature range as the resin content increases from 3 wt.% to 80 wt.%. In addition, zero thermal expansion is achieved in the La-Fe-Si/resin composite with 20 wt.% resin. The resin would reinforce the binding force by filling the pores between the particles. The La-Fe-Si/resin composite with 80 wt.% resin exhibits highly improved mechanical properties; for example, its compressive strength of 205 MPa is 75% higher than that of the La-Fe-Si/resin composite with 3 wt.% resin. The prepared La-Fe-Si/resin composites can be machined into different shapes for practical applications, such as thin plates, strips, and rods. Furthermore, the La-Fe-Si/resin composites can undergo 1000 thermal cycles without NTE performance degradation and mechanical integrity loss, indicating durable cycle stability. Hence, significantly tunable NTE with high mechanical properties and long-term cycle stability makes La-Fe-Si/resin composites present great application potential as NTE materials.

β-solidifying TiAl alloys are considered as promising candidate materials for high-temperature structural applications. Laser-based additive manufacturing (LAM) enables the fabrication of components with geometrical complexity in near-net shape, leading to time and feedstock savings. In this study, a gas-atomized Ti-44Al-4Nb-1Mo-1Cr powder is used as a feedstock material for LAM. However, the LAM of TiAl alloys remains a challenge due to serious cracking during the printing process. To minimize the cracking, the optimization of the LAM processing parameters is essential. Hence, the effects of the LAM processing parameters on the cracking susceptibility and microstructure are studied here. Our experimental results show that the cracking susceptibility can be mitigated by increasing the laser power. Accordingly, the microstructure transforms from the dominating α₂ grains to a near-lamellar microstructure with an increment in laser power, leading to a reduction in microhardness, even though it is still higher than that of its as-cast counterparts. It is concluded that changes in the laser power can directly tailor the microstructure, phase composition and microhardness of LAM-fabricated TiAl alloys.

Although near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) are desired for non-visible light source applications, the design of broadband NIR phosphors remains a challenge. Inspired by the chemical unit co-substitution strategy for the modification of composition and local structure, we realize a tunable redshift emission from 706 to 765 nm in garnet-type Lu₃Sc₂Ga₃O₁₂:Cr³⁺ with a broadened full width at half maximum and enhanced photoluminescence intensity by introducing a [Mg²⁺-Si⁴⁺] unit into the [Sc³⁺-Ga³⁺] couple. Structural and spectral analyzes demonstrate that the co-substitution reduces the local symmetry and crystal field strength of the [CrO₆] octahedra, thus leading to inhomogeneous widening of the ⁴T₂→⁴A₂ emission and enhanced blue absorption. Furthermore, the ⁴T₂→⁴A₂ emission exhibits a phonon-assisted character at low temperatures due to the thermal coupling effect with the ²E level. The fabricated NIR pc-LED based on the optimized NIR phosphor exhibits excellent potential in night vision and imaging applications.

Understanding the dynamic behavior of domain structures is critical to the design and application of super-elastic freestanding ferroelectric thin films. Phase-field simulations represent a powerful tool for observing, exploring and revealing the domain-switching behavior and phase transitions in ferroelectric materials at the mesoscopic scale. This review summarizes the recent theoretical progress regarding phase-field methods in freestanding ferroelectric thin films and novel buckling-induced wrinkled and helical structures. Furthermore, the strong coupling relationship between strain and ferroelectric polarization in super-elastic ferroelectric nanostructures is confirmed and discussed, resulting in new design strategies for the strain engineering of freestanding ferroelectric thin film systems. Finally, to further promote the innovative development and application of freestanding ferroelectric thin film systems, this review provides a summary and outlook on the theoretical modeling of freestanding ferroelectric thin films.