Materials Letters最新文献

The nanomechanical characteristics of Metal Inert Gas (MIG), Tungsten Inert Gas (TIG), and diffusion-bonded Inconel (IN718) and Austenitic Stainless Steel (SS 316L) were investigated. The nano hardness and elastic modulus of different weldments were evaluated using nanoindentation and compared. The results showed that intermetallic compounds (IMCs) and carbides were reduced with diffusion bonding. Moreover, maximum nano hardness and elastic modulus occurred in the welded zone (WZ) of TIG and MIG welded joints while at the bonding interface in diffusion bonding (DB). Lastly, the nano hardness of the bonding interface in diffusion-bonded was 11 % and 7 % lower compared to MIG and TIG welded joints.

In this work, the novel CoCrNi composite with as high fraction as 5 wt% TiC reinforcements were additively manufactured (AMed) by laser powder bed fusion (LPBF) of blended powders of nano-C particles, spherical micro-Ti powders and spherical CoCrNi powders, instead of blended powders of nano-TiC and CoCrNi powders. This method resulted in fully melting of C and Ti elements during laser fusion and subsequent precipitation of nano-TiC during solidification. The agglomeration of nano-TiC in the matrix is reduced by this method, resulting in an 1800 MPa ultrahigh strength, simultaneously maintaining a considerable elongation of 12 %. Rise in the fractions of TiC from 0 to 5 wt% reduces intensity of the texture and grain size in the matrix and convert the strong 〈1 0 1〉 texture to relative weak 〈1 0 0〉 texture along building direction (BD).

The microstructure evolution and mechanical properties of the (FeCrNi)₉₄Ti₃Al₃ medium entropy alloy, fabricated through selective laser melting, were investigated after warm-rolling. The as-built (FeCrNi)₉₄Ti₃Al₃ alloy exhibited a heterogeneous microstructure with alternating coarse face-centered cubic (FCC) phase grains (∼20 μm) and fine body-centered cubic (BCC) phase grains (∼1 μm). However, after warm-rolling and subsequent recrystallization, the alloy transformed into a dual-phase equiaxed grains structure consisting of FCC and BCC phases with an average grain size of approximately 2.8 μm. Additionally, the previously banded distribution of the BCC phase changed to a random distribution. Notably, during the deformation process, a twinning-induced plasticity (TWIP) effect was observed in the warm-rolled and recrystallized (FeCrNi)₉₄Ti₃Al₃ alloy, resulting in excellent ductility and a wide work-hardening platform.

Shape memory alloys (SMAs) have the potential to improve the efficiency of solid-state refrigeration technology through coupled excitation of multiple thermal effects. Aiming to achieve high elastocaloric NiMn-based SMAs, this paper utilized machine learning to predict the adiabatic temperature change and first-principle calculations to elucidate the mechanism. Based on the optimal XGB Regressor model, the Ni₅₀Mn₃₃Ti₁₇ SMA through directional solidification is predicted to have the highest adiabatic temperature change of 10 K (test temperature = 298 K, applied stress = 300 MPa). In addition, the volume change ratio after martensitic transformation reaches 2.375 % with first-principles calculations, which is expected to provide sufficient entropy and thus obtain an excellent elastocaloric effect. This study provides an available pathway to design and optimize the elastocaloric property of NiMn-based SMAs.

Epoxy-polycarbonate sandwiched films with enhanced dielectric performance were prepared in this study. Unlike traditional tedious multiple scratch-coating approach, the sandwich dielectric films were prepared based on a convenient solution-immersion process. Polycarbonate solutions with different concentration were applied to adjust the film composition and compared with epoxy-polycarbonate blending film. We found that rather than deteriorating the breakdown strength as shown in the blending counterpart, sandwiched films prepared by solution immersion shows superior breakdown strength (709.6 MV/m), almost 40 % better than both epoxy and polycarbonate components. Moreover, tan δ of the films prepared from solution-immersion (<0.005) is apparently smaller than blending samples (∼0.008). Both factors lead to admirable ideal dielectric energy storage performance (8.44 J/cm³) of the film, better than many conventional polymers.

Cr (VI) receives a lot of attention due to its toxicity and carcinogenicity. In this work, chlorella powder was used as a biochar source and combined with Cu-BTC to produce the Cu-BTC@BC composite material through a one-step solvothermal method. We found the optimal combination of removal efficiency and adsorption capacity at pH of 2, 25 °C and 0.5 g of Cu-BTC@BC at 100 mg/L. These results show that the Cu-BTC@BC has good Cr (VI) adsorption capacity and can be applied to the treatment of Cr (VI) in acidic wastewater.

Yb³⁺ and Er³⁺ co-doped Mg-substituted tricalcium phosphate (Mg-TCP) upconversion particles were synthesized using a two-step process: Single-phase Mg-TCP-Yb³⁺/Er³⁺ materials with an average particle size ∼ 130.2 nm can be obtained by the hydrothermal reaction at 180 °C for 24 h, followed by heat treatment at 800 °C for 4 h, which demonstrated excellent upconversion green luminescence around the 520/550 nm wavelength. The culture of MC3T3-E1 cells with the extraction medium from Mg-TCP-8%Yb³⁺/Er³⁺@800°C materials showed obvious proliferation with increase of culture time and noncytotoxicity. Additionally, the intracellular imaging of Mg-TCP-8%Yb³⁺/Er³⁺@800°C through endocytosis by cells demonstrated that the particles can be significantly degraded within 24 h, which showed great potential for bioimaging applications.

The equiatomic MoNbTaTiZr biocompatible and refractory high-entropy alloy (RHEA) was additively manufactured by laser powder bed fusion (LPBF). The possibility to reduce the cracking susceptibility of the RHEA during LPBF was investigated. By the addition of pure B to the RHEA powder feedstock, the in-situ precipitation of boride particles was promoted. These precipitates limited the grain growth, thus avoiding the formation of cracks.