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In this study, the Zn-0.5 wt%Zr (Zn-Zr) alloy was treated by laser surface remelting (LSR), and then the microstructure and degradation mechanism of the remelting layer were investigated and compared with the original as-cast alloy. The results reveal that after LSR, the bulky Zn22Zr phase in the original Zn-Zr alloy is dissolved and the coarse equiaxed grains transform into fine dendrites with a secondary dendrite arm space of about 100 nm. During the degradation process in simulated body fluid (SBF), the corrosion products usually concentrate at some certain areas in the original alloy, while the corrosion products distribute uniformly and loosely in the LSR-treated surface. After removing the corrosion products, it was found that the former suffers obvious pitting corrosion and then localized corrosion. The proposed mechanism is that corrosion initiates at grain boundaries and develops into the depth at some locations, and then leads to localized corrosion. For the LSR-treated sample, corrosion initiates at some active sites and propagates in all directions, corrosion takes place in the whole surface with distinctly uniform thickness reduction, while the localized corrosion and peeling of bulky Zn22Zr particles were eliminated. The electrochemical results also suggest the uniform corrosion of LSR-treated sample and localized corrosion of original sample. Based on the results, a new approach to regulate the corrosion mode of the biodegradable Zn alloy is proposed.

Recent studies have indicated a great demand to optimize the biocompatibility properties of pure Zn as an implant material. For this purpose, CaZn2(PO4)2·2H2O (CaZnP) was prepared using hydrothermal treatment (HT) combined with micro-arc oxidation (MAO) on pure Zn substrate to generate biodegradable implants. The polarization test and electrochemical impedance spectroscopy indicated that the MAO1−HT coating could modulate the corrosion behavior of MAO1 by filling the crevice between the coating and the substrate. Immersion test evaluation revealed that the osteogenic properties of MAO1−HT coating were better than that of pure Zn substrate, as evidenced by the molar ratio of Ca and P, which increased after soaking in simulated body fluid (SBF) for up to 10 days. In addition, L-929 cells cultured in the 100%, 50%, and 25% extracts of MAO1−HT coated samples exhibited excellent cytocompatibility. Meanwhile, cell adhesion was promoted on the surface with high roughness generated during MAO and HT processes. In summary, the calcified coatings improved biocompatibility and adjusted the degradation rates of pure Zn, broadening the application of Zn alloys.

The influence of Mg content on the mechanical properties, degradation behavior, in vitro cell adhesion, and in vivo behavior of as-extruded Zn–xMg–0.1Ca (x = 0.5 wt%, 1.0 wt%, 1.5 wt%) alloys was investigated. A high Mg content could increase the volume fraction of the hard Mg2Zn11 phase distributed at grain boundaries. This condition could significantly improve yield strength and ultimate tensile strength. Mg addition could adjust the degradation rate of Zn alloys and influence cytocompatibility. ZnMg1Ca0.1 alloy showed the highest adhesion density of bone marrow-derived mesenchymal stem cells (BMSCs) because the degradation rate of ZnMg1Ca0.1 alloy could supply appropriate pH and [Zn2+] for BMSCs. Mg addition could improve the cytocompatibility of Zn Mg Ca alloys. However, a Mg content threshold was observed, and the Mg content should be exactly controlled. Combined with the mechanical properties, the degradation rate of zinc alloy implants could be adjusted to match the healing of tissues by adding Mg. In vivo results showed that the degradation rate of the optimized Zn Mg Ca alloy could match the healing of local tissues or organs. Animal implant results revealed alloy safety.

In this study, heat treatment and extrusion were used respectively to optimize the microstructure of a novel Mg-2Y-1Zn-0.4Zr alloy, and its mechanical property, degradation behavior and cytocompatibility were investigated. Stress-strain curves showed that both heat treatment and extrusion could improve the mechanical properties of the alloy. Electrochemical results indicated that, comparing with as-cast specimen, the heat treated and as-extruded samples showed lower corrosion rate and less susceptibility to pitting corrosion. The cytotoxicity was evaluated using the methylthiazolyl diphenyltetrazolium bromide method via mouse fibroblast L929 cells. The results revealed that the cytocompatibility of Mg-2Y-1Zn-0.4Zr alloy was enhanced by heat treatment and extrusion. Besides, as-extruded alloy showed favorable mechanical property, the best degradation behavior and cytocompatibility which suggests that as-extruded may be a good candidate to be used in biomedical applications.

Ultra-fine-grained Zn-0.5Mn alloy was prepared by multi-pass hot extrusion. Minimum grain size of the Zn-0.5Mn alloy was about 0.35 µm, it exhibited room temperature superplasticity. During multi-pass extrusion, the pinning force of MnZn13 rendered the subgrains stable and restrained grain growth. The ultra-fine grain was finally formed.

Titanium alloy is a major structural material with excellent high specific strength in aerospace applications. Cubic boron nitride (cBN) is a synthetic wear-resistant material with high hardness, similar to that of diamond, that is used in mechanical cutting and grinding. In addition, the thermal stability of cubic boron nitride particles is much better than that of diamond. In order to further enhance the wear resistance of the Ti6Al4V alloy, the laser cladding (LC) technology characteristics of metallurgical bonding were used to prepare cubic boron nitride/Ti6Al4V and Ni-plated cubic boron nitride/Ti6Al4V composite coatings on Ti6Al4V substrates in this paper. However, in the laser molten pool, it is difficult to retain the raw properties of cubic boron nitride particles under laser radiation. Both composite coatings were analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The microstructures and interface bonding between cubic boron nitride particles and the Ti6Al4V matrix were examined using SEM, and the wear resistance and the worn track morphology of the composite coatings were evaluated using the ball-on-disc wear test and step profiler (WTM-2E). The results indicated that the Ni-plated cubic boron nitride/Ti6Al4V composite coating showed fewer thermal defects in comparison with the cubic boron nitride/Ti6Al4V coating. The Ni plating on the surface of cubic boron nitride particles was able to avoid the generation of thermal cracking of the cubic boron nitride particles in the composite coating. The TiN reaction layer was formed between the cubic boron nitride particles and Ti6Al4V matrix, which effectively prevented the further decomposition of the cubic boron nitride particles. The XRD and XPS results confirmed that the TiN reaction layer formed between the cubic boron nitride particles and Ti6Al4V. The Ni plating on the surface of the cubic boron nitride particles was also beneficial for increasing the wear resistance of the composite coating.

A composite coating composed of intermetallic compounds, Al&ndash, Si alloys, and an oxide ceramic layer was prepared on TA2 substrate by hot-dipping Al&ndash, Si alloy and micro-arc oxidation (MAO) methods. The microstructure and composition distribution of the resulting hot-dipped Al&ndash, Si alloy layer and MAO-caused ceramic layer were studied by scanning electron microscope (SEM) and energy dispersive spectrum (EDS). In addition, the phase composition of the diffusion layer obtained by the Al&ndash, Si alloy hot-dipping procedure was investigated by electron backscattered diffraction (EBSD), and the phase structure of the MAO-treated layer was studied by X-ray diffraction (XRD) analysis and X-ray photoelectron spectroscopy (XPS). The MAO method can make the hot-dipped Al&ndash, Si alloy layer in-situ oxidized to form a ceramic layer. Finally, a three-layer composite coating composed of a diffusion layer formed by the Ti&ndash, Al&ndash, Si interdiffusion, an Al&ndash, Si alloy layer and a ceramic layer was prepared on TA2 substrate. Compared with TA2 substrate, the TA2 sample with a three-layer composite coating has larger friction coefficient and less abrasion loss. The three-layer composite coating can significantly improve the wear resistance of TA2. A technical composite method was developed to the low cost in-situ growth of alumina-based ceramic wear-resistant coatings on TA2 substrate.

An ultrafine- and uniform-grained Zn–0.5Mn alloy (D3 alloy, stands for deformation rate of 99.5%) is fabricated via multi-pass drawing. The alloy features excellent ductility and elongation properties (up to 245.0% ± 9.0% at room temperature). Zn-0.5Mn alloys are composed of two phases, namely, Zn and MnZn13. The MnZn13 phase confers multiple effects during refinement by inducing and pinning low-angle boundaries within grains. Meanwhile, the presence of these phases along grain boundaries prevents the growth of new refined grains. D3 shows uniform corrosion behaviors in c-SBF solution on account of the even distribution of the MnZn13 phase in its microstructure. Animal implantation experiments indicate that D3 has good biocompatibility; it does not cause damage to bone tissue or other organs. Taking the results together, D3 may be developed into a new type of biodegradable material with remarkable elongation and corrosion properties and satisfactory biocompatibility for medical applications.

Diffusion of heavy rare earth elements (HREEs, Tb and Dy) after being coated on sintered Nd-Fe-B magnets by direct current magnetron sputtering was investigated. The results reveal that gain of the coercivity shows a higher efficiency of HREE consumption compared with other coating methods. The HREE diffuses along the grain boundary phase (GBP) deep into the magnet, an HREE-rich shell forms at the superficial layer of the diffused Nd2Fe14B grains, and the HREE in the magnets shows a dual-trend distribution. The diffusion of HREE includes a fast diffusion in the GBP and a slow diffusion in the grain phase (GP).

The effect of marine B. vietnamensis, isolated from East Sea, China, on the corrosion behavior of SAF 2507 duplex stainless steel (DSS) was studied. A flat plate bioreactor was used to simulate the marine environment. And the environmental parameters such as temperature, pH, flow rate and oxygen content were controlled in bioreactor which operated aerobically for 30 days with either inoculated or sterile artificial seawater. Electrochemical studies demonstrated a noticeable decrease in open circuit potential and an increase in current density in solutions containing B. vietnamensis compared to the sterile artificial seawater which confirmed the enhancement of corrosion rate of 2507 DSS in the presence of bacterium. FESEM images showed the presence of porous and heterogeneous biofilm and oxide layer on the 2507 DSS surface in the presence of bacterium. The heterogeneity of biofilm and different thicknesses of biofilm made the oxygen concentration cells on the 2507 DSS surface and induced localized corrosion at longer exposure times. The biofilm composition also identified by FTIR.

In order to improve the wear resistance and corrosion resistance of silver coating under electrical contact friction environment, Ag Sb coatings have been prepared via a non-cyanide electrodeposition process. The surface morphology, microstructure, microhardness, wear resistance, corrosion resistance and electrical resistivity of Ag Sb coatings have been studied and the effect of Sb content has been discussed. The non-cyanide electrodeposited Ag Sb coatings have a flatter and more compact surface morphology by comparison with the non-cyanide electrodeposited Ag coating due to the addition of KSbOC4H4O6 as Ag-plating brightener. The Ag 2Sb coating prepared from the bath containing 3 g·L−1 KSbOC4H4O6 obtains the highest microhardness of 146.5 HV and best wear resistance. The electrochemical testing results show a corrosion current density of Ag Sb coatings range from 1.14 × 10−5 A·cm−2 to 4.20 × 10−7 A·cm−2 whereas the Ag 2Sb coating achieves the best corrosion resistance.

Herein, pure Al coatings have been deposited on sintered NdFeB via multi-arc ion plating method. The effect of target current and working pressure on the microstructure and properties of these coatings have been investigated using scanning electron microscopy, laser scanning confocal microscopy, X-ray diffraction, tensile testing, electrochemical tests and neutral salt spray. The results showed that the Al coating on NdFeB magnets achieved higher deposition rate of 4.85 μm/h, a maximum adhesive strength of 24 MPa and a corrosion current density of two orders of magnitude less than that of bare NdFeB substrates when processed using a target current of 60 A and a working pressure of 1.0 Pa. Electrochemical impedance spectroscopy and neutral salt spray tests further proved the excellent corrosion protection performance of such thin films with a thickness of 5 μm without any significant perturbation on the magnetic properties of the substrate.

In this study, a biodegradable Zn-0.5 wt%Zr alloy was treated by laser surface remelting, and its surface microstructure, microhardness and corrosion resistance were investigated. The results reveal that the Zn22Zr phase in the original Zn-Zr alloy was dissolved and fine dendrites were formed in the remelting zone. The microhardness of the remelting zone increased to about 100 HV0.025 from 40 ∼ 50 HV0.025 of the original state. The LSR-treated surface shows much lower corrosion current and more positive corrosion potential than the original alloy, the simulated corrosion rate decreased obviously.

Grain boundary diffusion process (GBDP) of Tb on sintered Ce-substituted Nd-Fe-B magnets has been conducted by magnetron sputtering deposition of Tb film for coercivity enhancement. The microstructure and magnetic properties of the diffused (Nd,Ce)FeB magnets have been evaluated and the effect of diffusion temperature, time and Tb coating thickness on the Ce-substituted N35 magnets are discussed. The results show that a core-shell structure is formed around the main grains after GBDP, which promotes the coercivity enhancement of the magnets. A maximum coercivity enhancement from 10.9 kOe to 15.2 kOe is achieved in Ce-N35 magnets by deposition of 10 μm Tb films followed by diffusion processing at 900 °C for 300 min. The inhibition effect of Ce in GBDP of Tb is also evaluated using (Nd,Ce)FeB magnets with different Ce contents and discussed using diffusion model simulation implemented by Tb distributions through GD-OES. The rare earth element (REE)-rich nodes located at the triple junction of the grains may attribute to the Tb aggregation and the formation of TbFe2, resulting in the inhibition of further Tb diffusion.

Titanium has been added in the Al coatings on sintered NdFeB magnets by ion-beam-assisted magnetron sputtering to improve the mechanical properties of coatings without corrosion resistance deterioration. The effect of Ti addition on structure, mechanical and electrochemical properties of Al coatings has been investigated, complemented by x-ray diffraction and transmission electron microscopy. The results show that the ion-beam-assisted magnetron co-sputtering of Al and Ti obtains a single-phase polycrystalline structure of Al–Ti solid solution. With the increasing Ti content, the coating structure becomes denser and the grain size is reduced. Both the mechanical and wear properties of the coatings are improved with the addition of Ti where the hardness of the Al–Ti coating increases with the increasing amount of Ti. Polarization and EIS testing results show that the titanium-doped coatings have an enhanced corrosion resistance by comparison with pure Al coatings when Ti content is lower than 4.3 at.%.

The coatings of Cr2O3 were deposited on sintered NdFeB magnets by direct current (DC) pulse magnetron sputtering with and without ion beam at different O2 pressures. The coatings were compact and had a thickness of 1.8–2.2 μm. The coatings achieved a hardness up to 29 GPa and a wear rate of 1.78 × 10−7 mm3/Nm when ion-beam-assisted-deposition (IBAD) was used. Excellent anti-corrosion properties were obtained in the coating prepared by IBAD while the good magnetic properties of NdFeB substrate were retained. Electrochemical measurements revealed that the corrosion current density of the sample decreased from 4.66 × 10−6 A/cm2 (bare NdFeB) to 2.87 × 10−7 A/cm2 when O2 flux was 17 sccm during IBAD process.

Developing amorphous alloys with good corrosion resistance have attracted wide interests recently. In this work, a series of Fe71 − xCrxMo3.5Ni5P10C4B4Si2.5 (x = 0, 4, 8, 10, 12, 14 at.%) amorphous alloys are fabricated. Thermal stability of this alloy system increases slightly with appropriate Cr content. The corrosion resistance in 3.5 wt.% NaCl solution is sensitive to the minor addition of Cr (≤4 at.%) whereas higher Cr does not significantly improve the corrosion resistance according to the results of electrochemical measurements, SEM and XPS. These Fe-based amorphous alloys show comparable corrosion resistance with the well-known amorphous steel (Fe48Mo14Cr15Y2C15B6) despite the low Cr and Mo content, making them good candidates as corrosion-resistant coating materials. Keywords: Fe-based, Amorphous alloys, Corrosion, XPS

This paper presents a study of Stellite 6 powder deposited on medium-carbon steel over a range of laser deposition temperature, with emphasis on investigating the role of laser irradiation in the supersonic laser deposition (SLD) process. The peak coating thickness and the microhardness of the coating specimens produced with different deposition temperatures are measured to investigate the influence of laser irradiation on the coating characteristics. The coating bonding behavior is assessed via the analysis of interfacial element diffusion and fractured surface morphology under three-point-bending test. The results show that increasing the deposition temperature can improve the deposition efficiency significantly and induce interfacial element diffusion, which implies that the introduction of laser heat into cold spray (CS) permits a change in the thermodynamic state of impacting particles and substrate, thereby provides good interface bonding at lower velocities as compared with the CS process. This research finds that SLD is capable of producing Stellite 6 hardfacing with combined mechanical and metallurgical bonding.

In this study, a novel cobalt-free Fe40Mn20Cr20Ni20 (at.%) medium-entropy alloy (MEA) with low cost is purposively designed. The partially recrystallized microstructure was introduced into the single-phase FeMnCrNi MEA via thermo-mechanical processing. Surprisingly, the present MEA displays ultrahigh yield and ultimate tensile strengths of 1.2 and 1.34 GPa, respectively, and large ductility with a uniform elongation of 22% at 77 K. This is mainly due to the accumulation and entanglement of a large number of dislocations and the activation of deformation twins at 77 K.

The effect of heavy rare earth element (HREE, Tb and Dy) coating thickness on the grain boundary diffusion process (GBDP) of sintered Nd-Fe-B magnets is investigated. The distribution of HREE concentration fits well with the distribution depicted by the dual-trend diffusion model for the magnets with thin HREE coatings. However, when the HREE coating is thicker than a critical value, two new types of structures of HREE distribution, namely, the anti-shell/core structure and the transitional structure, besides the well-reported shell/core structure, appear sequentially around the Nd-Fe-B grains near the close surface of the diffused magnets. The evolution of the microstructures and the magnetic properties of the diffused magnets are further studied on the basis of the dual-trend diffusion model. The coercivity of the diffused magnets with thick HREE coatings slowly improves when anti-shell/core and transitional structures form on the outer layer of the diffused magnets. The ultimate coercivity of the HREE-diffused magnets is the result of the combined action of the above three structures.

A hot-dip aluminised layer was prepared on a Mo1 substrate and the obtained layer was oxidised in situ by a micro-arc oxidation (MAO) technique to form an oxide ceramic coating. The obtained hot-dip aluminised layer had a two-layer structure overall: the outer layer was a pure aluminium layer, and the inner layer was a diffusion layer. The hot-dip aluminising temperature directly influenced the structure and phase composition of the obtained diffusion layer. The diffusion layer of the hot-dip aluminised layer at 710 °C was divided into three layers. The inner, intermediate, and outer layers were mainly composed of Al8Mo3, Al4Mo, and Al12Mo phases, respectively. The diffusion layer of the hot-dip aluminised layer at 750 °C was divided into two layers: the inner layer was mainly composed of an Al8Mo3 phase, and the outer layer of Al4Mo. After the hot-dip aluminised layer was treated by MAO, a three-layer coating was obtained. The outer layer was a ceramic one obtained by MAO, which was mainly composed of Al2O3, mullite, and unoxidized aluminium. The middle one was pure aluminium obtained by hot-dip aluminising and without MAO. The inner layer was an Al–Mo diffusion layer.

A novel coating fabrication technique, known as supersonic laser deposition (SLD), which combines cold spray (CS) with laser technology, is applied to produce hard Ni60 (58–62 HRC) coating on medium carbon steel (AISI 1045 steel) substrate. Different process parameters are investigated to obtain the optimal. The Ni60 coating specimens prepared by SLD process are studied microstructurally using scanning electron microscope (SEM), energy dispersive spectrum (EDS) and X-ray diffraction (XRD). The microstructures of the coatings are compared with those of the coatings produced using laser cladding (LC). The hardness, tribological property and corrosion resistance of the Ni60 coatings produced by SLD and LC with the optimal process parameters are evaluated under Vickers hardness, pin-on-disk wear and electrochemical corrosion tests. It is demonstrated that the Ni60 coating with SLD exhibits some characteristics, such as fine microstructure as cast, stable phases and less dilution; it surpasses the coating produced with conventional LC process in sliding wear resistance; but in 1 mol/L H2SO4 solution, the SLD and LC coatings performed similarly in corrosion resistance. This research has proved that SLD technique enables depositing hard Ni60 on steel substrate, which is impossible for CS technique. Keywords: Supersonic laser deposition, Ni60 coating, Hardness, Wear, Corrosion, Dilution

Supersonic laser deposition (SLD) is a relatively new coating technique, which combines laser irradiation with cold spray (CS). The focus of this research is on the comparison between the WC/SS316L composite coatings produced by CS and SLD respectively, with respect to deposition efficiency, WC distribution and concentration, interfacial bonding, phases in the microstructures, and tribological properties, thus to highlight the beneficial effects of laser irradiation on the composite coating produced by cold spray process. The experimental results show that deposition efficiency, WC concentration and interface bonding of the composite coating can be improved by laser irradiation due to the softening of both powder particles and substrate. The SLD composite coating has the same phases as the CS coating does because of the relatively low heat involved in this process. The high concentration and strong interfacial bonding of WC particles in the SS316L matrix significantly improve the tribological properties of the SLD composite coating.

Cold spray (CS) is an emerging materials deposition technique in which metallic particles are accelerated to a high velocity in a supersonic gas flow and then impinged onto a substrate to form a coating at a temperature well below the melting point of sprayed materials. The coating microstructure and properties are greatly influenced by particle preheating and substrate softening. This article presents a study of CS process of copper powder, with assistance of synchronous laser irradiation. The influence of synchronous laser irradiation on the Cu coating characteristics was investigated. The results show that the coating surface with laser irradiation is smoother than that without laser irradiation. The peak coating thickness is increased by about 70% as synchronous laser irradiation is employed, indicating an improvement in deposition efficiency. It is also found that with synchronous laser irradiation the coating is denser and the coating-substrate interfacial bonding is better as compared with that without laser irradiation. Moreover, the EDS and XRD analyses find Cu oxidation occurrence in the SLD coating, but the oxide is trivial. The aforementioned improvements on the coating largely arise from particle preheating and substrate softening by synchronous laser irradiation in the CS process.

Although cold spray process has many unique advantages over other coating techniques, it has difficulties in depositing hard materials. This article presents a study in the beneficial effects of laser irradiation on the fabrication process of diamond/Ni60 composite coating using cold spray. The focus of this research is on the comparison between the composite coatings produced with laser cladding (LC) and with supersonic laser deposition (SLD), with respect to diamond graphitization and tribological properties, thus to demonstrate the beneficial effects of laser irradiation on the cold spray process. The influence of deposition temperature on the coating characteristics, such as deposition efficiency, diamond volume fraction, microstructure and phase is also investigated. The tribological properties of the diamond/Ni60 composite coating produced with SLD are determined using a pin-on-disc tribometer, along with the diamond/Ni60 coating produced using LC with the optimal process parameters for comparison. The experimental results show that with the assistance of laser irradiation, diamond/Ni60 composite coating can be successfully deposited using cold spray; the obtained coating is superior to that processed with LC, because SLD can suppress the graphitization of the diamond particles. The diamond/Ni60 composite coating fabricated with SLD has much better tribological properties than the LC coating.

The microsturcture and atmospheric corrosion of superplastic Zn-Al alloys with various Al contents was investigated in an industrial environment. With increased Al content, the corrosion rates of the four samples initially increased and then decreased. ZA8 alloy showed the lowest corrosion resistance, whereas ZA16 alloy showed the highest resistance, and ZA12 showed a resistance similar to ZA16. The Al-rich phase was prone to preferential attack when the superplastic ZA alloy was exposed to an industrial environment. However, the corrosion rate of the alloy decreased with increased Al content. The continuous Al-rich phase effectively blocked the corrosion process.

With the increasing demand for the clean sustainable power, the turbine design urgently turns to increase the capability significantly toward higher head for generating larger power. Currently, there are many studies in the field of the bulb turbine with single-stage runner, though reports about counter-rotating tandem-runner are rare. However, the further high-head application with the single-stage runner is very difficult to achieve due to the limit of the specific speed. In this paper, a new bulb turbine with the tandem-runner is designed in order to substantially increase the applicable limit toward higher head with larger power. A half of the net head is absorbed by the frontal runner which can generate output power, while the remaining half is absorbed by the rear runner. To generate the Euler energy required for the rear runner, the frontal runner has the counter-rotation against the rear runner so that the counter-rotating tandem-runner can meet the purpose of double head and power under the same size as the conventional bulb turbine. Supply and demand of Euler energy between the two runners are thoroughly optimized through the detailed flow analysis, in order to secure the stable operation. As a result, the interference of Euler energies between the outflow from the frontal runner and the inflow to the rear runner is confirmed to be very small on the counter-rotating interface between the two runners. The prediction method of on-cam performance between the two adjustable runners is also developed numerically, which provides optimal flow between the two runners. This research provides a theoretical basis for the optimal design and operation of the counter-rotating tandem-runner bulb turbines.

The influence of aluminium content on the corrosion behaviour of superplastic Zinc–Aluminium alloys immersed in simulated acid rain was investigated. ZA4, ZA8, ZA12, and ZA16 alloys were used for the test. The Al-rich phase was prone to preferential attack when the superplastic Zn–Al alloy was immersed for 5 d. However, with increasing ratios of the Al phase, the corrosion rates of the four samples decreased in the order ZA4 > ZA8 > ZA12 > ZA16. The corrosion rate of the alloy decreased with increasing Al content, which may be related to the distribution of the Al-rich phase. Corrosion kinetic parameters were also calculated.

The diffusion of Tb or Dy heavy rare earth elements (HREEs) coated on sintered Nd-Fe-B magnets by a direct current (DC) magnetron sputtering and its influences on microstructure, magnetic properties and electrochemical properties of the magnets were investigated. The results reveal that the HREE diffuses into the magnet and substitutes some of the Nd to form a (Nd1-x,HREEx)2Fe14B shell. The HREE concentration along the direction perpendicular to the sputtered coating surface shows a dual-trend distribution, which was considered to be induced by a fast diffusion in the grain boundary phase and a slow diffusion in the grain phase. The diffusion of DC magnetron sputtered metallic Tb or Dy shows higher efficiency of HREE consumption and greater gain of the coercivity compared with diffusion sources prepared by some other coating methods or consisted of HREE compounds. The coercivity increases from 14.6 kOe for a 5 mm thick original specimen to 24.0 kOe and 19.5 kOe for the Tb and Dy diffused specimens when the coating thickness on a double surface of the specimen is about 12.0 μm. The HREE-diffused magnets also show better corrosion resistance.

The atmospheric corrosion behaviour of cast and high pressure die-cast AZ91D alloy in a polluted environment were investigated by SEM, XRD and FTIR. The atmospheric corrosion rate of the ingot was higher than that of the die-cast specimen. SO 2 gas played an important role in atmospheric corrosion. The effects of dew condensation on the ingot were greater than that on the die-cast specimen. The corrosion was initiated in the less noble α phase of the samples. The β phase, on the other hand, remained and acted as a barrier to corrosion.

The microstructure evolution of thixomolding AZ91D magnesium alloy during heat treatment was investigated by means of SEM, XRD, and Vickers hardness measurement. The thixomolding AZ91D alloy has faster β phase dissolution kinetics in comparison with the HPDC alloy at 415 °C solution treatment. Both the discontinuous precipitation and the continuous precipitation were observed during aging treatment. The thixomolding specimen exhibited an accelerated age-hardening kinetics in comparison with the HPDC specimen.

The corrosion behaviour of die-cast AZ91D magnesium alloys in sulphate solutions was investigated by SEM, FTIR and polarization measurements. For immersion times less than 48 h, no pitting corrosion occurred and only generalized corrosion was apparent. According to the polarization curves, the corrosion rate order of the die-cast AZ91D Mg alloy in three aqueous solutions was: NaCl > MgSO 4 > Na 2 SO 4 . The main corrosion products were Mg(OH) 2 and MgAl 2 (SO 4 ) 4 ·22H 2 O in the sulphate solutions and the product film was compact. Precipitation of MgAl 2 (SO 4 ) 4 ·22H 2 O required a threshold immersion time.

A component for a mobile phone, made of AZ91D alloy, is manufactured by die cast. After chemical conversion treatment, it was found that there were some bright spots on the component surface. The formation mechanism of the bright spots was studied by means of SEM and metallgraphic microscope. The corrosion resistance of coatings was measured by potentiodynamic polarization test. The reason of bright spots formation is that the coarse primary α is dissolved into a dent during acid activation process because of little netted β and little aluminum. Besides, the coatings on bright spots are thin, the dimensions of primary α grains are large, and the surfaces are smooth relatively, so they are prone to reflecting light and become bright spots.

Supersonic laser deposition (SLD) is a newly developed coating method which combines the supersonic powder stream found in cold spray (CS) with synchronous laser heating of the deposition zone. The addition of laser heat energy into CS enables a change in the thermodynamic state of impacting particles and substrate, thereby significantly lowering the critical deposition velocities required for effective coating formation and allowing the range of materials deposited to expand to higher strength materials which are of considerable engineering interest.The work reported in this paper presents the ability of SLD technique to deposit hard metal matrix composite (MMC) coatings, such as WC/SS316L. The focus of this research is on the comparison between composite coatings produced with conventional CS and those produced with SLD. The microstructure evolution, mechanical deformation mechanisms, correlation between functional properties and process parameters were elaborated in detail. The experimental results show that with the assistance of laser irradiation, WC/SS316L composite coatings can be successfully deposited using SLD. The obtained coatings are superior to that processed with CS, because SLD can improve the deposition efficiency, coating density, interface bonding as compared to CS due to the softening of particle and substrate by laser irradiation. It can be found that SLD is capable of depositing high strength MMC coatings with good quality, thus exhibiting great potential in the field of metal three-dimensional printing.Supersonic laser deposition (SLD) is a newly developed coating method which combines the supersonic powder stream found in cold spray (CS) with synchronous laser heating of the deposition zone. The addition of laser heat energy into CS enables a change in the thermodynamic state of impacting particles and substrate, thereby significantly lowering the critical deposition velocities required for effective coating formation and allowing the range of materials deposited to expand to higher strength materials which are of considerable engineering interest.The work reported in this paper presents the ability of SLD technique to deposit hard metal matrix composite (MMC) coatings, such as WC/SS316L. The focus of this research is on the comparison between composite coatings produced with conventional CS and those produced with SLD. The microstructure evolution, mechanical deformation mechanisms, correlation between functional properties and process parameters were elaborated in detail. The experimental results sho...

Supersonic laser deposition (SLD) is a new coating and fabrication process in which a supersonic powder stream generated in cold spray (CS) impinges onto a substrate which is simultaneously irradiated with a laser. It will be increasingly employed for depositing coatings and metal additive manufacturing because of its unique advantages: solid-state deposition of dense, homogeneous and pore-free coatings onto a range of substrate, high build rate at reduced operating costs without the use of expensive gas heating and large volumes of helium gas, and opening up a new opportunity for efficiently depositing high hardness metallic powders which are usually difficult to be deposited solely by CS.Based on the current research results in our group, this paper systematically reviews the state of the art of supersonic laser deposition technique at home and abroad, from the viewpoints of materials selection, process optimization, properties characterization, equipment design and so on. The existing issues in these aspects are deeply analyzed and the corresponding solutions are tentatively proposed. Meanwhile, the potential industrial applications of supersonic laser deposition technique in various fields are elaborated in detail as well as the future perspectives and challenges facing this technology, in order to provide insight for further investigations and innovation in supersonic laser deposition as an emerging combination additive re-/manufacturing technology with high efficiency, low cost and high quality.Supersonic laser deposition (SLD) is a new coating and fabrication process in which a supersonic powder stream generated in cold spray (CS) impinges onto a substrate which is simultaneously irradiated with a laser. It will be increasingly employed for depositing coatings and metal additive manufacturing because of its unique advantages: solid-state deposition of dense, homogeneous and pore-free coatings onto a range of substrate, high build rate at reduced operating costs without the use of expensive gas heating and large volumes of helium gas, and opening up a new opportunity for efficiently depositing high hardness metallic powders which are usually difficult to be deposited solely by CS.Based on the current research results in our group, this paper systematically reviews the state of the art of supersonic laser deposition technique at home and abroad, from the viewpoints of materials selection, process optimization, properties characterization, equipment design and so on. The existing issues in these a...

High-entropy alloy is a novel material which consists of at least five principal elements with concentration ranging from 5 to 35 at. %. High-entropy alloy has lots of unique features such as excellent mechanical, magnetic and electrochemical properties etc. so that it has potential to serve as surface protective coatings. In this research, a Fe CrNiCoMn high-entropy alloy powder is fabricated using gas atomization process and this powder is deposited on medium carbon steel substrate by laser cladding. The microstructures of the alloy powder and laser-cladding coating are analyzed using scanning electron microscopy (SEM), energy dispersive spectrum (EDS) and X-Ray diffraction (XRD). The hardness of the coating is measured with a microhardness tester. The resistance to high temperature softening of the coating is also investigated under the annealing treatment performed at 300 °C, 500 °C and 700 °C for 4 h respectively. The experimental results show that the alloy powder processed by gas atomization method has better sphericity, and the coating exhibits a microstructure of single face center cubic (FCC) phase, mainly composed of ellipsoidal dendrites and interdendrites. The phase in the microstructure of the coating remains unchanged after the annealing treatments and the morphology has little change below 550 °C annealing treatments but it has obvious change after 700 °C annealing treatment. The hardness of the coating does not change with the annealing treatments.High-entropy alloy is a novel material which consists of at least five principal elements with concentration ranging from 5 to 35 at. %. High-entropy alloy has lots of unique features such as excellent mechanical, magnetic and electrochemical properties etc. so that it has potential to serve as surface protective coatings. In this research, a Fe CrNiCoMn high-entropy alloy powder is fabricated using gas atomization process and this powder is deposited on medium carbon steel substrate by laser cladding. The microstructures of the alloy powder and laser-cladding coating are analyzed using scanning electron microscopy (SEM), energy dispersive spectrum (EDS) and X-Ray diffraction (XRD). The hardness of the coating is measured with a microhardness tester. The resistance to high temperature softening of the coating is also investigated under the annealing treatment performed at 300 °C, 500 °C and 700 °C for 4 h respectively. The experimental results show that the alloy powder processed by gas atomization method...