High-energy Mechanical Alloying Method Research Articles

Nanostructured Ni(Zn)–Al2O3 cermet particle synthesis in high-energy mechanical alloying method (CG-3:IL07)

Ceramic-metallics (cermets) have emerged as an important class of composite material combining favorable properties of their constitutive phases. In this work, nanostructured cermet Ni(Zn)–Al2O3 composition was synthesized using the high-energy mechanical alloying (HE-MA) method to be deployed as a cold spray deposition powder feedstock. Pre-milled Ni(Zn) alloy particles were mechanically mixed followed by milling in a SPEX™ 8000 M High Energy Ball Mill at a fixed 1050 rpm. The material design-of-experiment (DoE) involved two design compositions (30 wt% and 50 wt% α-alumina) with two substitutional alloy compositions, Ni(5 wt%Zn) and Ni(10 wt%Zn), along with milling time as a process variable. Microstructural characterization confirmed the embedment of nanoscale Al2O3 grain in micron-scale Ni(Zn) alloy particles. Additionally, EBSD analysis of Ni(Zn) alloy particles revealed that Ni(5 wt%Zn) experienced more uniform plastic deformation, work hardening and subsequent fracturing when compared to Ni(10 wt% Zn) alloy particles. The particle size measurement was carried out by laser diffraction showed that the cermet particles milled for 4 h had the desired size range for the objective of cold spraying. Also, the embedment of alumina into the Ni(Zn) alloy matrix and thereby, homogenization of cermet particles enhanced with the increase in milling time.

Microstructure and thermal conductivity of Cu-Cu2AlNiZnAg/diamond coatings on pure copper substrate via high-energy mechanical alloying method

In the present work, a novel system of Cu2AlNiZnAg high entropy alloys (HEAs) powder was successfully synthesized and Cu-Cu2AlNiZnAg/diamond coatings were fabricated on T2 pure Cu substrate via mechanical alloying method. Characterization of the Cu2AlNiZnAg HEA powder indicated that a single FCC solid solution phase was formed and no indication of any amorphous phase or intermetallic compound was found in the microstructure. The FCC phase was Cu-rich phase. The coatings exhibit a microstructure composed of black particles of diamonds and gray areas of Cu2AlNiZnAg HEA reinforced Cu matrix composites. The effects of Cu-Cu2AlNiZnAg/diamond ratio and milling time on the fabrication of coatings were investigated. The effect of annealing treatment on the microstructure of coatings was discussed. The microhardness of the coating was far higher than that of copper substrate whether it was annealed or not. The thermal conductivity of the fully coated sample was improved greatly after annealing, reaching 358.53W•m−1•K−1, which was superior to the T2 pure copper with the same annealing treatment.

Microstructures evolution, formation mechanisms and properties of Sicp/ Al composite coatings on Ti-6Al-4v substrate via mechanical alloying method

In this present work, high-energy mechanical alloying method was successfully applied to fabricated Al-SiC coatings, which possessed a composite structure. The coatings fabricated by different Al-SiC weight ratio were studied. The results of scanning electron microscope(SEM) and Energy Dispersive X-ray spectrometer(EDS) revealed the microstructures and phase compositions of as-synthesized coatings, respectively. To test the mechanical properties of coated samples prepared at different Al content, the tests of microhardness value were carried out from the outermost coating to the inner substrate. Then, the effect of milling duration on coatings was also studied. Adhesion behaviors of the coatings at different milling time were investigated through scratch tests. And friction and wear resistance were also tested. Which further confirmed the surface strengthening effect of the coating. The formation mechanisms of the Al–SiC composite coating and Al–SiC composite powder were elaborated. Overall consideration of microstructure, phase composition and mechanical properties, the coating prepared with Al–SiC raw powder ratio of 65:35 at 7 h milling time was the optimal processing parameters on fabrication of Al–SiC composite coating. The Al–SiC coating shows high performance in adhesion behaviors and wear resistance, this method is capable to be applied to fabricate coatings on the inner walls of tubular specimens .

Oxidation behavior of Cr-AlSi12 composite coatings on Ti-6Al-4V alloy substrate fabricated via high-energy mechanical alloying method

In this paper, to protect Ti-6Al-4V alloy from oxidation, the Cr-AlSi12 composite coatings were successfully prepared on Ti-6Al-4V substrate by high-energy mechanical alloying method. The effects of powder weight ratio and milling duration on the fabrication of the coatings were studied. The addition of AlSi12 restricted the formation of microholes and the microstructure was homogenized at suitable milling time. The high-temperature oxidation resistance of the coatings was evaluated by oxidation mass gain. The coating consists of two layers, one is the inner layer with large particles of Cr and the other is the outer layer with highly homogenized structure. The formation process of the coatings was studied. The as-prepared coating could significantly improve oxidation resistance of the substrates, which is mainly due to the following two points. First, the formation of Al2O3 oxide layers, AlCr and CrSi intermetallic phases inside the coating were favourable to densification of the coating, thereby preventing the diffusion of oxygen. Second, a thin Si-rich layer formed at the coating-substrate interface could effectively prevent further diffusion of oxygen. The coated samples prepared using weight ratio 60:40 and milling time of 5 h, which exhibited lowest oxidation mass gain value and excellent microstructure, was the optimum parameter.

Microstructures and oxidation behavior of Al-CrMnFeCoMoW composite coatings on Ti-6Al-4V alloy substrate via high-energy mechanical alloying method

In the present work, CrMnFeCoMoW high entropy alloy powder and Al- CrMnFeCoMoW composite coatings were successfully synthesized on Ti-6Al-4V alloy substrate via mechanical alloying method. The final milling products for as-milled CrMnFeCoMoW high entropy alloy powder consist of body-centered cubic (BCC) and face-centered cubic (FCC) solid solution phases. The composite coatings exhibit a composite structure consisting of white high entropy alloy particles and Al-rich gray regions. The adhesion of the coating was tested by scratch experiment. The effects of the ratio of Al-CrMnFeCoMoW powder ratio and milling time on the preparation of composite coatings were investigated. The microstructure and element distribution and phase composition of the coating had been studied. The results show that under the optimal parameters, the thickness of the coating is 180 μm, which shows a good bonding with the Ti-6Al-4V alloy substrate. The high temperature cyclic oxidation test was carried out at 850 °C. The oxidation resistance of the coating was compared with that of the traditional oxidation resistant coating. The composite coating obviously exhibits better oxidation resistance than traditional coating.

Nanocrystalline Al2O3-Ni(Cr) particle synthesis by high-energy mechanical alloying method

Nanostructured feedstock material results in better surface protective coatings under high-temperature oxidation erosion environment. This research paper focuses on synthesizing ceramic-metallic (cermet) nanostructured Al2O3-Ni(Cr) feedstock particles using high-energy mechanical alloying (HE-MA) powder processing technology. The underscoring particle design objectives were twofold: (1) reduce the ceramic oxide grain size below 20 nm, and more pressingly (2) embed nano-scaled grains inside metal/alloy binder particles, hence the nanostructured cermet particles. The novelty of this research work lies in the successful embedment of nanostructured Al2O3 grains into the micron sized Ni(Cr) metallic binder matrix. In a SPEX mill with a milling speed of 1200 rpm along with variation in milling time following two separate material design compositions (design of experiments) it was possible to meet the stated objectives. Results show good conformance between the experimental and analytical data in terms of obtaining Al2O3 grain reinforced Ni(Cr) nanostructured particles with mean grain and particle sizes standing at 19 ± 1.15 nm and 15 μm ± 4.6 μm, respectively, after 12 h of milling.

Microstructures and oxidation behavior of NiCrAlCoY-Al composite coatings on Ti-6Al-4V alloy substrate via high-energy mechanical alloying method

In the present work, NiCrAlCoY-Al gradient composite coatings were successfully fabricated on Ti-6Al-4V alloy substrate via high-energy mechanical alloying method. The microstructures and elemental and phase composition of the coatings have been studied. Effects of both NiCrAlCoY-Al powder ratio and milling time on the fabrication of composite coating were investigated. The NiCrAlCoY-Al weight ratio 65:35 was considered the optimal powder ratio to fabricate the coating at the selected milling parameters. The high-temperature cyclic oxidation tests were performed at 850 °C and 750 °C. The fabricated sample using 65:35 wt ratio and 4 h milling time showed the best oxidation resistance due to the low mass gain, rutile TiO2 undetected surface, and densified composite cross-section morphology. The decreased oxygen content of the oxidized cross-section line scanning results revealed the improvement of oxidation resistance. The oxidation process of the as-fabricated coating had been divided into five steps. Three protective Al2O3 oxide layers together with other alloy compounds could prevent the further diffusion of oxygen. The coating could enhance the oxidation resistance of the substrate.

Microstructures and properties of W–Cu functionally graded composite coatings on copper substrate via high-energy mechanical alloying method

In the present work, process of gradual addition of powders was proposed to prepare W–Cu functionally graded composite coatings on copper surface via high-energy mechanical alloying method using a planetary ball mill. The microstructures and elemental and phase composition of mechanically alloyed coatings were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS). Fully dense and uniform triple layer W–Cu (W–30wt.% Cu+W–15wt.% Cu+W–7wt.% Cu) functionally graded composite coatings was metallurgically bonded on the pure copper substrate, with an average thickness of ∼92μm. Microhardness test and friction and wear test were carried out to examine the mechanical properties of the coatings. The results showed that the maximum microhardness of the triple layer gradient coatings reached HV0.1 212, showing a threefold improvement upon the pure copper substrate. And the cross-sectional microhardness values of the processed sample changed gradually, which gave a proof for the cushioning and sustaining functions of the W–Cu functionally graded composite coatings. The friction coefficient of the as-fabricated triple layer W–Cu functionally graded composite coatings was 0.5 and the corresponding wear mass loss was only 2.8mg, which was obviously lower than that of the pure copper substrate. A reasonable formation mechanism of W–Cu functionally graded composite coatings prepared by process of gradual addition of powders via high-energy mechanical alloying method was presented.

Fabrication of Ti–Cu–Al coatings with amorphous microstructure on Ti–6Al–4 V alloy substrate via high-energy mechanical alloying method

A high-energy planetary ball mill was applied to fabricate Ti–Cu–Al coating on Ti–6Al–4V alloy substrate. The microstructure and elemental and phase composition of coatings were studied. The surface SEM images showed that the rough but densified coating surfaces, the cross-section microstructures as well as the related EDS line scan results illustrated different structures in the coatings, and the XRD results as well as TEM and corresponding SEAD pattern provided evidences of the existence of amorphous phase in the coatings. Mechanical properties including microhardness and friction and wear behavior were tested respectively. The microhardness testing results indicated that the fabricated coatings could largely strengthen the substrate surface. And the friction and wear resistance were tested with a ball-on-block sliding configuration, with the testing results showing decrease in both friction coefficients and wear weight loss after mechanical alloying treatment. The analysis and testing results also showed that a proper increase in the applied milling time favored the improvement in the thickness, surface smoothness, densification level, microstructural and chemical homogeneity as well as amorphization degree of the deposited coating. On the basis of two significant action mechanisms associated with a planetary ball mill, a reasonable mechanism was presented for the formation of amorphous phase contained coatings on Ti–6Al–4V alloy substrate.

Preparation of Ti–Cr and Ti–Cu flame-retardant coatings on Ti–6Al–4V using a high-energy mechanical alloying method: A preliminary research

The Ti–Cr and Ti–Cu coatings with the in situ forming intermetallic phases were fabricated on the substrates of Ti–6Al–4V alloy using a novel high-energy mechanical alloying method. The coatings exhibited the flame-retardant function on the common Ti alloy which was characterized by the phenomena of spontaneous combustion under some certain environmental conditions. The solid-state processing to prepare the flame-retardant coatings was finished in a planetary ball-mill with a further designed vial. Some stable intermetallic phases were formed on the basis of the initial instable non-equilibrium phases during the mechanical alloying processes. Using the optimized process parameters, the suitable diffusion layer appeared at the interface of the coating and the inner surface of substrate. The effects of the milling durations on the formation quality of coatings were emphasized. Following the analyses of the experimental results, the formation mechanisms of the deposited coatings prepared by the mechanical alloying method were detailed in terms of four assumed steps. The coating adhesion strengths were evaluated by scratch tests and then measured according to ASTM G171-03 Standard. The flame-retardant functions of Ti–6Al–4V substrates with Ti–Cr and Ti–Cu coatings were evaluated through the laser spot melting testing on the surfaces.

Development of NiFe-CNT and Ni3Fe-CNT nanocomposites by mechanical alloying

NiFe-CNT and Ni3Fe-CNT nanocomposites were fabricated by high energy mechanical alloying method. X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and optical microscopy were employed for evolution of phase composition, morphology and microstructure of the powder particles. Ball milled powders were heat treated at 500°C for 1h to release the milling induced stresses. Bulk samples were prepared by sintering of cold pressed (300MPa) samples at 1040°C for 1h. XRD patterns of powders, as-milled and after annealing at 500°C did not show any peak related to CNTs or excess phases due to the interaction between CNTs and matrix. SEM micrographs showed that the addition of CNTs caused a reduction of powder particles size. The hardness value of as-milled NiFe and Ni3Fe powders reach to 660 and 720HV, respectively. According to optical microscopy evaluations, the amount and size of the porosities of the composites bulk samples decreased in comparison with matrix ones.