The inherent brittleness and limited toughness of bulk metallic glasses (BMGs) remain critical challenges for their application as structural engineering materials. In this study, ultrasonic excitation was applied to Zr_58.75Cu_21.15Fe_4.7Al_9.4Nb₆ BMG with the aim of enhancing its mechanical performance. The results reveal that ultrasonic treatment significantly increases the fracture toughness by approximately 28% and induces a pronounced plastic deformation plateau following yielding. This improvement in both strength and ductility is attributed to the formation of nanoscale crystalline phases and ultrasound-induced phase separation within the amorphous matrix, which collectively promote shear band multiplication and inhibit crack propagation.

WC-based cermet coatings with a CoCrNiAlTi binder were fabricated on 04Cr13Ni5Mo stainless steel substrates using the atmospheric high-velocity air–fuel (HVAF) spraying process. The influence of the air-to-fuel ratio (AFR) on the microstructure, mechanical properties, and wear resistance of the WC-CoCrNiAlTi coatings was systematically investigated. The results indicate that the WC-CoCrNiAlTi coatings primarily consisted of WC, (Co, Ni)₃W₃C and a face-centered cubic (FCC) binder phase. As the AFR increased, the formation of the (Co, Ni)₃W₃C phase gradually decreased. Concurrently, the coating density improved, which was attributed to the enhanced particle melting state and increased flight velocity, leading to better flattening upon impact. The average microhardness of the WC-CoCrNiAlTi coatings gradually increased with an increasing AFR. The coating produced at an AFR of 1.130 exhibited the highest microhardness of 1355.68 HV_0.2. Both the friction coefficient and the wear rate of the coatings decreased progressively as the AFR increased. At the optimal AFR of 1.130, the coating demonstrated the lowest friction coefficient (0.6435) and wear rate (1.15 × 10⁻⁶ mm³·N⁻¹·m⁻¹), indicating a wear resistance 34.85 times that of the stainless steel substrate. Furthermore, the slurry erosion weight loss rate of the WC-CoCrNiAlTi coatings decreased gradually with increasing AFR. The coating sprayed at an AFR of 1.130 showed the minimum erosion rate (1.70 × 10⁻⁶ g·cm⁻²·min⁻¹), which was 24.04 times lower than that of the substrate. The erosion mechanism of the WC-CoCrNiAlTi coatings was identified as the fatigue-induced removal of WC particles under alternating stress. The ductile high-entropy alloy (HEA) binder effectively protects the brittle WC phase through adaptive deformation, thereby significantly mitigating coating damage.

To enhance the operational damage resistance of hydraulic machinery, this study employed laser cladding technology to fabricate a Co_37.4Cr₃₀Ni₂₀Al₅Ti₅Nb_2.6 high-entropy alloy coating on 04Cr13Ni5Mo substrate. The influence of laser power on the microstructure and properties of the coating was systematically investigated. Based on preliminary research, the friction-wear performance and cavitation erosion behavior of the coatings prepared at 3000 W, 3200 W, and 3400 W were specifically examined. Results indicate that as the laser power increased from 3000 W to 3400 W, the microhardness of the coating gradually decreased from 345.3 HV_0.2. At 3000 W, the precipitation of trace strengthening phases significantly enhanced the mechanical properties. In wear tests under a 20 N load for 30 min, the wear rate of the coating prepared at 3000 W was 1.41 × 10⁻⁴ mm³/(N·m), which is 13.5% lower than that of the 3200 W coating (1.63 × 10⁻⁴ mm³/(N·m)) and 16.07% higher in wear resistance compared to the substrate. Cavitation erosion tests revealed that after 20 h of ultrasonic vibration, the mass loss of the 3000 W coating was only 2.35 mg, representing an 88.89% reduction compared to the substrate (21.15 mg), and significantly lower than that of the 3200 W (4.57 mg) and 3400 W (3.85 mg) coatings. This study demonstrates that precise control of laser power can effectively optimize the cavitation erosion resistance of high-entropy alloy coatings, providing technical support for their application in harsh environments.

Using fluxing technology, molten Fe₈₀P₁₄B₆ alloy achieved significant undercooling (ΔT). Experimental results demonstrate that the solidified morphologies of the Fe₈₀P₁₄B₆ alloy vary considerably with ΔT. At ΔT = 100 K, the microstructure is dendritic. At ΔT = 250 K, a variety of eutectic morphologies are observed, including a network-like structure near the solidification center, attributed to liquid spinodal decomposition. At ΔT = 350 K, the microstructure exhibits a uniform, random network-like morphology with approximately 50 nm. The mechanical property of the specimens solidified at different ΔT was checked by microhardness test, indicating that the hardness of the specimens increases with the increase in ΔT, reaching a maximum value of 1151 HV_0.2.

Multi-principal element alloy (MPEA) Fe_66.5−xCr₂₄Ni₈Nb_1.5Ti_x coatings were fabricated via laser cladding on Q235 steel substrates to enhance their surface performance. This study revealed that the Ti content within these MPEAs directly influences the properties of the resulting coatings. The experimental results demonstrated that increasing the Ti content in the Fe_66.5−xCr₂₄Ni₈Nb_1.5Ti_x MPEA promoted the formation of a BCC phase, significantly enhancing the coatings’ mechanical properties. Specifically, the effect of Ti content on the microstructure and properties of the laser-clad MPEA coatings was investigated. Detailed analyses of the coatings’ friction and wear performance, as well as cavitation erosion resistance, were conducted. Under a 20 N load for 30 min, increasing Ti content reduced the wear rate from 4.41 × 10⁻⁵ mm³/(N·m) to 3.79 × 10⁻⁵ mm³/(N·m), resulting in a 14.06% improvement in wear resistance. Cavitation erosion (CE) tests showed that after 20 h of ultrasonic exposure, the sample with x = 2.1 exhibited a cumulative mass loss of 4.92 mg, compared to 8.12 mg for the sample with x = 0.3. This represents a 39.4% reduction in cavitation erosion mass loss for the higher-Ti-content coating. In stark contrast, the Q235 substrate incurred a significantly higher mass loss of 86.78 mg under identical conditions. This signifies a dramatic enhancement in cavitation erosion resistance achieved by the high-Ti MPEA coating. These findings demonstrate a novel approach to enhancing the cavitation erosion resistance of MPEA claddings by optimizing Ti content, thereby broadening their potential application scope in harsh environments.