This review examines the methods used to optimize the process parameters of laser cladding, including traditional optimization algorithms such as single-factor, regression analysis, response surface, and Taguchi, as well as intelligent system optimization algorithms such as neural network models, genetic algorithms, support vector machines, the new non-dominance ranking genetic algorithm II, and particle swarm algorithms. The advantages and disadvantages of various laser cladding process optimization methods are analyzed and summarized. Finally, the development trend of optimization methods in the field of laser cladding is summarized and predicted. It is believed that the result would serve as a foundation for future studies on the preparation of high-quality laser cladding coatings.

Different-shaped ultrafine MoNbTaW high-entropy alloy powders were firstly prepared by a convenient mechanical alloying method. The phase composition and microstructure of the powders were characterized. The powders are ultrafine with nano-sized grains and a good homogeneous microstructure. All the powders have a single body-centered cubic solid solution phase and form the high-entropy alloy during mechanical alloying. These powders with different shapes are quite attractive for developing high-performance MoNbTaW high-entropy alloy bulk and coatings combined with a following sintering, spraying, or additive manufacturing technique.

TiMoNbZr_x refractory high-entropy alloys were prepared by vacuum arc melting, and the influence of the Zr alloying element and its content on the phases, microstructure, mechanical properties, and wear resistance of TiMoNbZr_x alloys was explored. It was found that the alloys after Zr addition were composed of a single BCC phase. Upon increasing the Zr content, the grain size of the as-cast alloy decreased first and then increased, and TiMoNbZr_0.5 exhibited the smallest grain size. Adding an appropriate amount of Zr increased the strength and hardness of the alloys. TiMoNbZr_0.5 exhibited the best wear resistance, with a friction coefficient of about 0.33. It also displayed the widest wear scar, the shallowest depth, and the greatest degree of wear on the grinding ball because of the formation of an oxide film during wear.

Single-crystal silicon carbide (SiC) has been widely applied in the military and civil fields because of its excellent physical and chemical properties. However, as is typical in hard-to-machine materials, the good mechanical properties result in surface defects and subsurface damage during precision or ultraprecision machining. In this study, single- and double-varied-load nanoscratch tests were systematically performed on single-crystal 4H-SiC using a nanoindenter system with a Berkovich indenter. The material removal characteristics and cracks under different planes, indenter directions, normal loading rates, and scratch intervals were analyzed using SEM, FIB, and a 3D profilometer, and the mechanisms of material removal and crack propagation were studied. The results showed that the Si-plane of the single-crystal 4H-SiC and edge forward indenter direction are most suitable for material removal and machining. The normal loading rate had little effect on the scratch depth, but a lower loading rate increased the ductile region and critical depth of transition. Additionally, the crack interaction and fluctuation of the depth-distance curves of the second scratch weakened with an increase in the scratch interval, the status of scratches and chips changed, and the comprehensive effects of the propagation and interaction of the three cracks resulted in material fractures and chip accumulation. The calculated and experimental values of the median crack depth also showed good consistency and relativity. Therefore, this study provides an important reference for the high-efficiency and precision machining of single-crystal SiC to ensure high accuracy and a long service life.

We report here structural and directional magnetic susceptibility measurements on single crystals of ${\mathrm{Y}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Pr}}_{\mathit{x}}$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ (x=1.0, δ=1, 0.11; x=0.7, δ=0; and x=0.42, δ=0.22). The space group of ${\mathrm{PrBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_6$ (Pr-O6) and ${\mathrm{Y}}_{0.58}$ ${\mathrm{Pr}}_{0.42}$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{6.78}$ (Pr 0.42-O7) were found to be P4/mmm and that of ${\mathrm{PrBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{6.89}$ (Pr-O7) was found to be Pmmm. Also, Pr-O7 was found to be weakly orthorhombic. Directional, magnetic susceptibility measurements in the temperature range 2–300 K revealed a clear peaking in the paramagnetic anisotropy of Pr-O7 around 17 K, and ${\mathrm{\chi }}_{\mathit{c}}$≳${\mathrm{\chi }}_{\mathit{a},\mathit{b}}$ at all temperatures. However for ${\mathrm{Y}}_{0.3}$ ${\mathrm{Pr}}_{0.7}$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ (Pr0.7-O7) and Pr0.42-O7, ${\mathrm{\chi }}_{\mathit{c}}$≳${\mathrm{\chi }}_{\mathit{a},\mathit{b}}$ at room temperature and ${\mathrm{\chi }}_{\mathit{c}}$<${\mathrm{\chi }}_{\mathit{a},\mathit{b}}$ for temperatures below 110 and 60 K, respectively. The magnetic susceptibilities have been analyzed in the light of crystalline electric-field effects considering J mixing of all the thirteen multiplets. Intermediate coupled wave functions have also been used in the calculations. Crystal-field interaction is found to be stronger in the case of Pr-O7 compared to Pr-O6 which is also evident from a shorter Pr-O bond length in the case of Pr-O7 than in Pr-O6. A best set of eigenvalues and eigenfunctions has been determined and these are discussed and compared with inelastic neutron scattering data. © 1996 The American Physical Society.