This paper presents a method of ultrasonic-assisted laser metal deposition of Al-12Si alloy. The effects of the ultrasonic power and remelting treatment on the development of porosity, microstructural evolution, and tensile properties of the deposits were investigated. The results suggested that a combination of an ultrasonic vibration and remelting treatment could prolong the existence of the molten pool and the effect of the ultrasound. Therefore, the density of the samples increased from 95.4% to 99.1% compared to the as-prepared samples. The ultrasonic action in the molten pool could not only increase the density of the samples but also refine the grains and improve the tensile properties of the samples. Metallographic observation showed that the maximum size of the primary α-Al dendrites were refined from 277.5 µm to 87.5 µm. The ultimate tensile strength and elongation of the remelting treatment samples with ultrasonic vibration were ~227 ± 3 MPa and 12.2% ± 1.4%, respectively, which were approximately 1.17 and 1.53 times those of the as-prepared samples, respectively. According to the tensile properties and fracture analysis, the density increase dominated the improvement of the mechanical properties.

Ultrasonic-assisted laser metal deposition (UALMD) technology was used to fabricate Al 4047 parts. The effect of the powder feeding laser power, remelting laser power and ultrasonic power on the relative density of the parts was investigated. The relative density, microstructure and mechanical properties of the specimens obtained by the optimized process parameters were compared with the corresponding properties of the cast alloys. The results showed that dense alloys with a maximum density of 99.1% were prepared using ultrasonic vibration and by remelting the previously deposited layer with the optimized processing parameters, and its density was almost equivalent to that of the cast parts. The microstructure of the samples using optimal laser parameters presented columnar Al dendrites and equiaxed Si particles at the boundary of each deposited layer, while the supersaturated Al solid solution was transformed into equiaxed crystal surrounded by fine fibrous Si phases at the center of the layer. Moreover, the size of the primary Al and the Si particles in the samples produced by UALMD was remarkably refined compared to that of the primary Al and Si particles in the cast structure, resulting in grain refining strengthening. The observed variation in the microstructure had an obvious impact on the tensile properties. The mechanical behavior of the deposit obtained by UALMD revealed superior tensile strength, yield strength and tensile ductility values of 227 ± 3 MPa, 107 ± 4 MPa and 12.2 ± 1.4%, which were approximately 51%, 38% and 56% higher than those of the cast materials, respectively.

This study, investigated the powder flow field for multiangle laser cladding, bridging theoretical gaps in the repair of metal parts with tilted and complex surface, specifically those are immovable and nonrotatable. Initially, a multiangle computational fluid dynamics-discrete element method gas-powder coupling model was established. It can consider not only the continuity characteristics of gas as a fluid, the discreteness characteristics of powder as particles, but also the mutual influence relationship. Subsequently, the response surface method was used to explore the optimal combination of carrier argon gas rate (A), the powder-feeding rate (B), and the protective argon gas rate (C) at different deflection angles, with the powder collection rate as the optimization objective. Analysis of variance results for the powder collection rate indicated that the significance of the factors and their interaction terms were ranked as A > B > AB at 0° and 30°, A > B > BC at 60°, A > B > C > BC at 90°, and C > A > BC > AB at 120° and 150°. Furthermore, the relative errors between predicted and simulated values, as well as simulated and powder collection experimental values, the single-pass experimental values were within 2%, 3%, and 7%, indicating the model was valid and reliable. Finally, the optimal combinations of carrier argon gas rate, powder-feeding rate, and protective argon gas rate were obtained, achieving high powder collection rates. These research findings offer theoretical guidance for selecting and optimizing process parameters in multiangle laser cladding.

Multiangle laser cladding, in which the cladding head is deflected at different angles, is an advanced surface modification technology that is widely used in the repair of metal parts with complex surfaces. Nevertheless, the powder flow was affected by gravity, causing decreasing powder utilization and degrading coating quality. In this paper, to reveal the gas-powder flow mechanism, the coupled models based on the computational fluid dynamics-discrete element method (CFD-DEM) were developed. They can consider not only the continuity characteristics of gas as a fluid, the discreteness characteristics of powder as particles, but also the mutual influence relationship. Subsequently, a series of simulations and experiments were conducted in which the cladding head was deflected at angles of 0°, 30°, 60°, 90°, 120°, and 150°. The results demonstrated that with the increase in the deflection angle, the maximum powder concentration gradually declined from 16.49 to 9.80 kg m−3, the diameter of the powder spot increased progressively from 2.66 to 5.31 mm, and the powder collection rate dropped significantly from 45.11% to 27.95%. Finally, the models were experimentally validated and proved to be accurate. The findings of this research revealed the mechanism of the gas-powder flow and provided theoretical guidance for the selection and optimization of process parameters in mutiangle laser cladding.

According to the propagation performance of B-ultrasonic waves in the human skeleton, nano-hydroxyapatite/polyurethane composites with potential application as bone materials for manufacturing high precision and multiple tissues simulated foetus phantom were synthesised by in-situ polymerisation. The composite (nano-hydroxyapatite/polyurethane) was prepared by reacting castor oil, with nano-hydroxyapatite and isophorone diisocyanate, extended with 1, 4-butanediol. The thermal stability was measured by thermogravimetric analysis. The specific groups were assessed by Fourier transform infrared spectroscopy. The morphology and diameters were examined by scanning electron microscopy. The B-scan ultrasonic image was diagnosed by B-ultrasonic testing. The results showed that when the nano-hydroxyapatite addition was 37%, nano-hydroxyapatite dispersed evenly throughout the polyurethane matrix, and its B-scan ultrasonic image was obviously clear.