To enhance the high-temperature wear resistance of MCrAlY coatings, 10 wt% MoSi2 particles were incorporated into a CoNiCrAlY coating via oscillating laser-directed energy deposition (OL-DED). The wear behavior of the coatings was systematically evaluated at room temperature, 500 degrees C, and 900 degrees C. Results indicate that the highly dynamic OL-DED molten pool promotes complete decomposition of MoSi2, leading to uniform diffusion of Mo and Si and the in-situ formation of high-hardness (Cr, Mo)3(Co, Ni)5Si2 and beta phases uniformly dispersed within the gamma-phase matrix. This microstructure provides synergistic wear resistance: the hard phases resist abrasion and plastic deformation, while the soft gamma-phase absorbs strain energy. Increased hard-phase content also raises overall hardness, inhibiting subsurface deformation and preventing crack propagation in the protective oxide scale. Compared to the baseline CoNiCrAlY coating, the CoNiCrAlY-10MoSi2 coating exhibits a lower friction coefficient and wear rate at all temperatures, with advantages becoming more pronounced at high temperatures. At 900 degrees C, its average friction coefficient decreases significantly from 1.19 to 0.89, and the wear rate decreases from 0.62 x 10-4 mm3 center dot N- 1 center dot m- 1 to 0.48 x 10-4 mm3 center dot N- 1 center dot m- 1, a reduction of approximately 29.2 %.

Al-based nanoporous films are synthesized via femtosecond pulsed laser deposition using TiB2/AlSi10Mg composite precursor powders. Optical microscopy, scanning electron microscopy, X-ray diffractions, Raman spectroscopy, and time-domain thermoreflectance spectroscopy are used to evaluate the morphology, microstructure, phase transition, and thermal conductivity. Results indicate that femtosecond pulsed laser facilitated a layerplus-island growth mode, resulting in nanoparticle clusters in size of 20-50 nm with tunable porosity due to the so-called "cold ablation" mechanism. This induces a very low thermal conductivity of 0.0267 W/(m center dot K), is close to that of air. As the increased fraction of TiB2 from 10 wt% to 70 wt% in original precursor powders, the thermal conductivity increases from 0.0267 W/(m center dot K) to 0.2072 W/(m center dot K), which is attributed to that the increased elements of TiB2 cause more TiO2. Formation of TiO2 results in more uniform and densified structures that lead to a rapid increase in thermal conductivity.

The transient thermal cycling characteristics during laser powder bed fusion (LPBF) induce elemental segregation and columnar growth, resulting in significant mechanical anisotropy and strength–ductility trade-off in titanium alloys. In order to break through this bottleneck, this work proposes a strategy of inducing equiaxation of columnar grains through recrystallization and regulating the morphology of the α″ phase (from an acicular shape to nanoparticles) to synergistically optimize the uniformity, strength and ductility of LPBF-fabricated Ti-35Nb-5Cu- x Mo (Ti355 x, x = 0, 1, 2, 4 wt%) alloys. The results demonstrate that LPBF-fabricated Ti355 x alloys display equiaxed/columnar microstructures with significant mechanical anisotropy and strength–ductility trade-off. After tailored solution heat treatment at 950 ℃, the Ti3552 alloy (HT950-Ti3552) achieves chemical homogenization and thermally driven equiaxation of columnar grains, leading to excellent isotropic mechanical properties. Concurrently, the morphology of α″ is transformed from an acicular-shaped to nanoparticle. As a result, the interactions between dislocations and α″ nanoparticles promote cross slip, thereby homogenizing plastic flow and delivering high ductility (>25%) for the HT950-Ti3552 alloys during tensile deformation. Moreover, the addition of Mo increases the dislocation density and enhances the solute drag effect, leading to refined β grains and α″ nanoparticles, which in turn increase the yield strength (YS) of the HT950‐Ti3552 alloy by about 90 MPa compared to that of the HT950‐Ti355 alloy. This work establishes a theoretical basis and technical route for developing LPBF-fabricated β-type titanium alloys with isotropic mechanical properties and an improved balance between strength and ductility.

Obtaining excellent wear resistance is critical for titanium alloys used as orthopedic implants. In this study, the [3-type Ti-35Nb-5Cu-xMo alloys (Ti355x, x = 0, 1, 2, and 4 wt%) were fabricated by the laser powder bed fusion (LPBF) method. In the meantime, the influence mechanism of Mo content on the microstructure and tribological properties was systematically investigated. The results show that all the LPBF-produced Ti355x alloys exhibit a bimodal columnar-equiaxed grain structure, with Mo refining columnar grains and suppressing the alpha '' phase formation. Moreover, increasing the Mo content reduced the relative density, while enhancing the microhardness. However, tribological responses exhibited an initial decrease followed by an increase with increasing Mo content. When the Mo content reached 2 wt% (in Ti3552 alloy), the friction coefficient and the wear rate decreased to similar to 0.76 and similar to 3.8 & times; 10-4 mm3 N-1 m-1 , respectively, whereas both parameters (similar to 0.80 and similar to 4.3 & times; 10-4 mm3 N-1 m-1) significantly increased when the Mo content rose to 4 wt%. This phenomenon stems from the exceptional hardness homogeneity of the Ti3552 alloy (with the Weibull shape parameter of similar to 18.2), which facilitated continuous TiO2 film formation and suppressed the stress-concentration-induced fracture, enhancing the wear resistance.

TiB2 was introduced through a self-developed Al-Si alloys flux-cored wire, and TiB2 reinforced Al-Si composites were successfully fabricated via wire arc additive manufacturing (WAAM). Subsequently, the comprehensive influence of TiB2 particles on the formation mechanism of pores, the evolution of grain structure, and mechanical properties was studied. The results demonstrated that pores originated from hydrogen in the molten pool and the air carried by the flux-cored wire, which migrated and aggregated in the molten pool and mainly concentrated near the fusion boundary. The incorporated TiB2 particles significantly modified solidification behavior, migrating to grain boundaries under the combined effects of force, where they simultaneously pinned boundaries and promoted heterogeneous nucleation. This dual effect refined grain structure and promoted equiaxed crystals throughout deposited layers. Compared with the Al-Si alloys sample, the TiB2/Al-Si composites sample strength increased to 182.44±2.15 MPa and 163.70±5.27 MPa in the horizontal and vertical directions, respectively. However, the elongation decreased to 10.21±0.59% and 4.89±0.68% in the horizontal and vertical directions, mainly due to the excessive pores. This study provides a viable WAAM strategy for fabricating Al matrix composites with controllable microstructure-property relationships.

To enhance the limited strength of as-printed AlMgErZrSc alloys, cost-effective Cu was introduced into the AlMgErZrSc system via laser powder bed fusion (LPBF). A systematic investigation was conducted to study the effect of Cu content (1, 3, 5, 7 wt%) on microstructure and mechanical properties. The results demonstrate that increasing Cu content from 0 to 7 wt% can enlarge the width of the fine equiaxed zone (FEZ) at the molten pool boundaries from 1.5 +/- 0.17 mu m to 13.3 +/- 0.93 mu m-a ninefold enhancement. This microstructural evolution is driven by Cu-induced constitutional supercooling and heterogeneous nucleation of Al-3(Sc,Zr) precipitates, which synergistically facilitate the formation of fine equiaxed grains. At Cu concentrations >= 3 wt%, the eutectic reaction is activated, stabilizing the precipitation of S-Al2CuMg. This process consumes Mg, suppressing beta-Mg2Si formation and creating competitive precipitation dynamics. The nanoscale S-Al2CuMg and beta-Mg2Si distributed at the grain boundaries of alpha-Al matrix generate a pinning effect, effectively impeding dislocation movement and strengthening the alpha-Al matrix. However, adding excessive Cu (7 wt%) can lead to high dislocation density (similar to 1.41 x 10(15) m(-2)) and coarse secondary S-Al2CuMg, thereby inducing stress concentration and a reduction in ductility. Therefore, the AlMgErZrSc-5Cu alloy exhibits an enhanced ultimate tensile strength of 534 +/- 8 MPa and elongation of 8.6 +/- 0.9%. The Cu-induced strengthening mechanisms include: (i) solid-solution strengthening of Cu, (ii) grain-boundary strengthening of alpha-Al, (iii) dislocation strengthening, and (iv) precipitation strengthening from L1(2)-Al-3(Sc,Zr)/S-Al2CuMg/beta-Mg2Si nano-phases.

Additive manufacturing of high-strength aluminum alloys faces two fundamental limitations: crack susceptibility and strength-ductility trade-offs. To address these challenges, we propose an in-situ alloy design strategy to spatially modulate the microstructure in AlMgErZr alloys during laser powder bed fusion (LPBF) by introducing 316L stainless steel as a functional additive. With increasing 316L content, solute-induced constitutional undercooling promotes a transition in grain morphology from columnar to cellular/dendritic, resulting in hierarchical heterostructure. At the optimal 2.5 wt%316L addition, the alpha-Al matrix is partitioned by submicron-tomicron cellular network consisting of amorphous Al-Fe-Ni nanoprecipitates, coherent L12-Al3(Er, Zr) and incoherent Mg2Si precipitates. This design creates a multi-element effect that promotes amorphous phase formation through strongly negative Al-Fe-Ni mixing enthalpies as the thermodynamic driver, combined with enhanced configurational entropy and atomic size mismatch from large-radius (Er, Zr, Sc) and solid-solution (Mg, Cr) elements. The cellular network serves as a reinforcement carrier and coordinates plastic deformation to homogenize strain, thereby enabling multiple strengthening mechanisms: amorphous precipitates enable interface-mediated dislocation annihilation and Orowan strengthening, while L12 nanoprecipitates contribute through ordering and anti-phase boundary effects. Additionally, Cr solid solution induces lattice distortion of alpha-Al, and the Fe and Ni from 316L refine equiaxed grains. Consequently, the as-printed AlMgErZr-2.5 wt%316L alloy exhibits an ultimate tensile strength of 587 MPa with 10.5% elongation. Especially, post-aging further enhances strength to 686 MPa (retaining 5.4% elongation), attributed to L12 re-precipitation at both amorphous/alpha-Al and alpha-Al/alpha-Al interfaces. This work establishes a framework for designing crack-resistant, high-performance aluminum alloys via in-situ engineering of amorphous/crystalline heterostructures.

Cu-316L-xMo immiscible alloys were manufactured by laser powder bed fusion (LPBF) in this work. The oxidation behavior of three types Cu-316L-xMo alloys at 600 degrees C and 700 degrees C were studied to reveal the influence of Mo on the oxidation kinetics, oxide scale formation and integrity. The results showed that a heterogeneous oxide layer composed of CuO and Fe2O3 was formed on the surface after oxidation, and locally varying oxide-thicknesses is observed due to the immiscibility of epsilon-Cu and gamma-Fe phases. The incorporation of Mo ions into the oxide scale accelerates the oxidation rate of Cu-316L-xMo alloys. The high volatility of MoO3 compromises the integrity of the oxide scale, especially at higher temperature. Moreover, the growth and thermal stresses developed within the oxide scale during thermal cycling leads to severe cracking and spallation of the oxide scale.

To improve the oxidation resistance of CoNiCrAlY alloy, 10 wt% MoSi2 was introduced into the material using oscillating-laser directed energy deposition (OL-DED). A comparative study of the microstructural evolution and isothermal oxidation behavior between the CoNiCrAlY and CoNiCrAlY-10MoSi2 alloys was conducted. The results show that adding MoSi2 with a low coefficient of thermal expansion (CTE) promotes the formation of intermetallic compounds ((3 and (Cr,Mo)3(Co,Ni)5Si2 phase), reduces the CTE mismatch between oxide scale and CoNiCrAlY-10MoSi2 alloy, mitigates the risks of oxide scale cracking/spalling, and increases the service temperature of CoNiCrAlY-10MoSi2 alloy by over 100 degrees C (to 1100 degrees C). Furthermore, the (Cr,Mo)3(Co,Ni)5Si2 phase in CoNiCrAlY-10MoSi2 alloy immobilizes Cr/Mo via high-temperature element-trapping effect, suppressing volatile MoO3 formation and inhibiting detrimental spinel oxides (e.g., Co(Ni)Cr2O4), maintain the oxide scale integrity. This mechanism maintains protective scale integrity and synergistically enhances oxidation resistance.

To improve the oxidation resistance of CoNiCrAlY alloys, varying contents of MoSi2 were introduced into the alloys fabricated via oscillating laser-directed energy deposition (OL-DED). The microstructural evolution and isothermal oxidation behavior of the CoNiCrAlY-xMoSi2 alloys (x = 0, 5, 7, 10, and 12 wt.%) were systematically investigated. Results show that greater MoSi2 additions facilitate β phase formation and lower the Al threshold required to develop a continuous Al2O3 scale. This leads to a transition in the oxide scale from a double-layer structure (Co(Ni)Cr2O4 + Al2O3) to a single-layer Al2O3. Notably, when the MoSi2 content exceeds 5 wt.%, Laves phase precipitates form around the β phase, creating a unique core-β/shell-Laves structure. This structure effectively suppresses grain boundary diffusion of Al atoms, promoting lattice diffusion and facilitating the formation of a uniform and dense Al2O3 scale. The optimal MoSi2 addition of 10 wt.% results in a weight gain of only 0.36 mg/cm² after oxidation at 1000 °C for 500 h, representing a 62.1 % reduction compared to the undoped CoNiCrAlY alloy. These findings demonstrate that the OL-DED-fabricated CoNiCrAlY-10MoSi2 alloy exhibits superior oxidation resistance, outperforming other MCrAlY alloys at 1000 °C.

To improve the oxidation resistance of CoNiCrAlY alloys, varying contents of MoSi2 were introduced into the alloys fabricated via oscillating laser-directed energy deposition (OL-DED). The microstructural evolution and isothermal oxidation behavior of the CoNiCrAlY-xMoSi2 alloys (x = 0, 5, 7, 10, and 12 wt.%) were systematically investigated. Results show that greater MoSi2 additions facilitate (3 phase formation and lower the Al threshold required to develop a continuous Al2O3 scale. This leads to a transition in the oxide scale from a double-layer structure (Co(Ni)Cr2O4 + Al2O3) to a single-layer Al2O3. Notably, when the MoSi2 content exceeds 5 wt.%, Laves phase precipitates form around the (3 phase, creating a unique core-(3/shell-Laves structure. This structure effectively suppresses grain boundary diffusion of Al atoms, promoting lattice diffusion and facilitating the formation of a uniform and dense Al2O3 scale. The optimal MoSi2 addition of 10 wt.% results in a weight gain of only 0.36 mg/cm2 after oxidation at 1000 degrees C for 500 h, representing a 62.1 % reduction compared to the undoped CoNiCrAlY alloy. These findings demonstrate that the OL-DED-fabricated CoNiCrAlY-10MoSi2 alloy exhibits superior oxidation resistance, outperforming other MCrAlY alloys at 1000 degrees C.

This work reports on a systematic investigation of the microstructure and comprehensive performance of Cu–Fe immiscible composite coatings prepared through the combination of mechanical alloying and laser cladding. The samples were characterized by scanning electron microscopy with an energy dispersive analysis, X-ray diffraction, a digital microhardness tester, a current tester, an electrochemical analyzer, and a magnetometer. The results show that the immiscible composite coatings are mainly composed of α-Fe particle dispersion in the ε-Cu matrix due to liquid phase separation, and this is exacerbated by the addition of more Fe content. Concentrated distribution of Fe-rich particles at either the top or bottom of the immiscible composite coatings is driven by the dominant mechanism of Marangoni and Stokes motion. With the increased fraction of Fe content, the microhardness and electrical resistivity increased, but with a degradation in corrosion resistance. With the increased ball milling time, the electrical resistivity increased, and the corrosion resistance improved. Compared to the medium-carbon steel substrate, the immiscible composite coatings can achieve an improved corrosion resistance, as well as a maximum saturated magnetization of 10.172 emu/g and the lowest coercivity at 17.249 Oe.

Friction stir processing (FSP) significantly improves the microstructure and mechanical properties of wire arc additive manufacturing (WAAM) components. This study pioneers the application of submerged friction stir processing (SFSP) to thin-walled WAAM components fabricated from Al-2319, Al-5087, and Al-6082 alloys. The samples were characterized by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, electron backscatter diffraction, and microindentation. The results demonstrate that SFSP leads to a break of the eutectic network, the uniform distribution of precipitates originating from the Al matrix, a marked reduction in porosity and cracks, and grain refinement attributed to accelerated dynamic recrystallization, enhancing hardness and ductility across all three alloys. The improvement was most notable in the Al-6082 alloy relative to the others. Water cooling delays precipitates formation and encourages the development of fine particles. The uncoarsened theta' phase in Al-2319 and the fine beta' phase in Al-5087 both contribute to superior tensile properties.

Recent studies have shown that the thermal conductivity (kappa) of single-walled carbon nanotubes (SWCNTs) can dramatically change due to structural changes within the same sample. This introduces substantial uncertainty to interfacial thermal resistance (ITR) measurement, which usually relies on pre-measured kappa. Herein, we implement a novel transient Raman technique to distinguish and simultaneously measure the kappa and ITR of a SWCNT bundle of less than 10 nm by employing multiple laser heating sizes, each carrying distinct information about the ITR and kappa. The ITR is measured as 975-1200 K m W-1 whereas kappa is 180-246 W m-1 K-1. The ITR shows a decreasing trend against increased bundle size, demonstrating the impact of contact area in local energy transport. The measured kappa is approximately 33 % of supported graphene reported in literatures. This significant kappa reduction is attributed to the structural defects in the sample and the bundling effect consistent with earlier studies.

The Zn-3Mg alloy fabricated by laser powder bed fusion (LPBF) additive manufacturing is widely used in biomedical implants due to its excellent biocompatibility and favorable mechanical strength. However, its application is hindered by limited ductility and a relatively rapid degradation rate. This study investigated the influence of annealing heat treatment on the microstructure, mechanical properties, and degradation behavior of LPBF-fabricated Zn-3Mg porous implants. A systematic analysis of various annealing parameters revealed the evolution mechanisms of the microstructure, including grain coarsening and the precipitation and distribution of secondary phases Mg2Zn11 and MgZn2. The results indicated that appropriate annealing conditions (such as 250 °C for 1 h) significantly enhanced the compressive strain by 10%, while maintaining a high compressive strength of 24.72 MPa. In contrast, excessive annealing temperatures (e.g., 365 °C) promoted the formation of continuous brittle phases along grain boundaries, leading to deterioration in mechanical performance. The degradation behavior analysis illustrated a substantial increase in the corrosion rates from 0.6973 mm/year to 1.00165 mm/year after annealing at 250 °C for 0.5 h and 365 °C for 1 h, which can be attributed to the micro-galvanic effect induced by the presence of fine or coarse secondary phases that promoted localized corrosion. This study demonstrated synergistic regulation of mechanical properties and degradation behavior in the Zn-3Mg porous structures through optimized heat treatment, thereby providing essential theoretical and experimental supports for the clinical application of biodegradable zinc-based implants.

Additively manufactured NiTi-based shape memory alloys (SMAs) can achieve good superelasticity at specific temperatures. However, the realization of superelasticity over a wide temperature range in additively manufactured NiTi-based SMAs has rarely been reported. To the best of our knowledge, this is the first study to present the in situ synthesis of (Ni50.4Ti49.6)95Cu5 ternary SMA via laser powder bed fusion (LPBF) additive manufacturing process using a mixture of pre-alloyed Ni50.4Ti49.6 and elemental Cu powders to expand the temperature range for applications of superelastic NiTi-based SMAs via additive manufacturing. The alloy displayed relatively good compressive recovery strain (1.54-2.40 %) within the temperature range from - 50-50 degrees C. The distorted Ti(Ni, Cu) B2 austenite matrix and high-density stacking faults formed because the supersaturated Cu atoms significantly strengthened the matrix and impeded dislocation formation during stress-induced martensitic transformation. In addition, supersaturated Cu atoms introduced numerous lattice distortion regions into Ti2(Ni, Cu) precipitates and impeded dislocation movement, effectively strengthening the matrix. The synergistic effect of these factors contributes to the superelasticity of LPBF (Ni50.4Ti49.6)95Cu5 over a relatively wide temperature range. These findings pave the way for achieving superelasticity over a wide temperature range in LPBF NiTi-based SMAs.

Ti6Al4V alloys, widely used as dental and orthopedic implants, suffer from tribocorrosion by cyclic loads from patient activity, resulting in cell damage and implant failure. This work investigates the corrosion resistance, tribocorrosion, and antibacterial performance of Ti6Al4V-xCu (x = 0, 1, 3, and 5 wt%) alloys for potential use as metal implants. The alloys were fabricated using laser powder bed fusion (LPBF) and subsequently heat treated at 800 degrees C for 1 hour followed by 600 degrees C for 1 hour. The results revealed that the microstructure of Ti6Al4V-xCu alloys is composed of alpha and nano-Ti2Cu phases, where the volume fraction of Ti2Cu increases from 0.6 % (1 wt% Cu) to 5.8 % (5 wt% Cu). As a result, the tribocorrosion volume of Ti6Al4V-5Cu alloy is reduced by similar to 37.5 % compared with Ti6Al4V, and its antibacterial rate is 91.4 %. The enhanced tribocorrosion is attributed to the formation of in-situ passivation film, the self-lubrication action of Cu, the gradient nano-grain strengthening of deformation driven and the precipitation strengthening of nano-Ti2Cu. Moreover, the enhanced antibacterial ability is attributed to the combined mechanisms from the electrostatic bonding of Cu ions and the contact-killing of Ti2Cu phase to bacteria. Therefore, the Ti6Al4V-5Cu alloy with alpha and nano-Ti2Cu phases can be used as a promising candidate for superior biomedical implants.

Nonequilibrium among phonon branches critically influences nanoscale heat transport yet remains largely unexplored in one-dimensional (1D) systems, particularly at cryogenic temperatures. This work reports the first experimental quantification of optical-acoustic phonon coupling factor (GOA) in single-walled carbon nanotubes using the frequency-domain energy transport state-resolved Raman technique at cryogenic and room temperatures. Remarkably, a strong suppression of GOA is observed at low temperatures that exceeds the suppression of the coupling of interfacial phonon modes. As temperature increases, GOA is found to increase monotonically, consistent with enhanced anharmonic decay processes of optical phonons. At 93 K, the optical-acoustic phonon temperature difference exceeds 75% of the acoustic phonon temperature rise, which is reduced to about 33% at room temperature. The critical role of laser heating size on phonon nonequilibrium is elucidated, where it gets amplified for a more confined heating size. By utilizing the recently developed equivalent interfacial medium model, the intrinsic temperature-dependent interfacial thermal conductance based on acoustic phonon temperature is obtained. The results show that neglecting the nonequilibrium among phonon branches overestimates the interfacial conductance by ≈30% at room temperature. This research provides fundamental insights into phonon nonequilibrium in 1D nanoscale materials that strongly impact next-generation nanoelectronics and solid-state energy converters.

To improve the wear performance of CoCrAlYTa coating, part of the carbon nanotubes (CNTs) chemically reacted with Ta to form reinforcement phase (TaC), while the other CNTs were retained as lubrication phase. Subsequently, the CoCrAlYTa-xCNTs (x = 0, 1, 2, and 4; wt

Cu-Fe-P immiscible alloys characterized by heterogeneous lamellar structure were manufactured by laser powder bed fusion (LPBF) and the deformation behavior of LPBF-produced immiscible alloys was investigated systematically. When the linear energy density of 133 J/m is adopted during LPBF, the immiscible alloy exhibits the highest compressive strength (-1 GPa) and engineering strain (-27%). The high strength of the LPBF-produced immiscible alloy is attributed to the heterogeneous lamellar structure including the interconnected Fe2P layer and nano-Fe2P particles as "hard" phase dispersed in the epsilon-Cu matrix as the "soft" phase. Moreover, the good ductility is attributed to the fine epsilon-Cu grains as "soft" phase precipitated within the lamellar Fe2P due to the secondary liquid phase separation (SLPS). This "soft-hard-soft" heterogeneous microstructure can effectively delay crack growth to exhibit excellent mechanical properties in the LPBF-produced immiscible alloys.