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New-type magnesium alloy with prominent solubility and mechanical property lays foundation for preparing fracturing part in petroleum extraction. Herein, Mg-xZn-Zr-SiC alloy is prepared with casting strategy. Electrochemical and compression tests are conducted to assess the feasibility as decomposable material. Morphology, composition, phase and distribution are characterized to investigate decomposition mechanism. Results indicate that floccule, substrate component and reticulate secondary phase are formed on as-prepared surface. Sample also acts out enhanced compression strength to maintain pressure and guarantee stability in dissolution process. Furthermore, as decomposition time and zinc content increase, couple corrosion intensifies, resulting in gradually enhanced decomposition rate. Rapid sample decomposition is mainly due to basal anode dissolution, micro particle exfoliation and poor decomposition resistance of corroding product. Such work shows profound significance in preparing new-type accessible alloy to ensure rapid dissolution of fracturing part and guarantee stable compression strength in oil-gas reservoir exploitation.

Comprehensive experiments including monotonic tension and monotonic compression of specimens taken from a rolled AZ31B Mg thick plate along five different material orientations with respect to the rolled direction (RD), and free-end torsion of a tubular specimen machined along the thickness direction (ND) were conducted. The experimental results were used to evaluate an elastic-viscoplastic self-consistent model with the consideration of twinning and detwinning (EVPSC-TDT) on magnesium (Mg) alloys. The EVPSC-TDT model provides stress-strain curves and the hardening rates in close agreement with the experimental results of all the 11 loading cases. The model adequately predicts the textures after fracture of all the 11 loading cases and the evolutions of tension twins with increasing strains for tension in the ND, compression in the RD, and torsion along the ND. The Swift effect was observed in the experiment and was properly simulated by the model.

RE-containing magnesium alloys were prepared via molten-salt-mediated magnesiothermic reduction by using RE2O3 (RE=Y, Nd and Gd) and Mg metal as raw materials. The thermomechanical analysis of the magnesiothermic reduction reactions in molten salt was investigated. Then the molten-salt-mediated magnesiothermic reduction process was studied from three different perspectives. After that, the RE-containing magnesium alloy was characterized by using chemical analysis, XRD analysis and SEM analysis. The magnesiothermic reduction was a liquid-liquid reaction with relatively weak driving force. During the melting process and the magnesiothermic reduction process, magnesium metal and the obtained alloy went up and down as a whole in molten salt, which improved the process safety without introducing chloride inclusions. Meanwhile, the hydrolysis of the RECl3-containing molten salt occurred at elevated temperature, which severely impeded the magnesiothermic reduction process. After the magnesiothermic reduction at 750 °C for 2.0 h, the content of RE and the common impurity elements in the obtained RE-containing alloy met the both requirements of the commercial WE43A and WE43B.

To overcome the limitation in formability at room temperature, manufacturers have developed magnesium alloys with remarkable properties by adding rare-earth elements. The rare-earth magnesium alloys behave differently from the conventional alloys, especially with respect to their coupled anisotropic and strain rate sensitive behavior. In the current work, such behavior of the rare-earth Mg alloy ZEK100 sheet at room temperature is investigated with the aid of the elastic viscoplastic self-consistent polycrystal plasticity model. Different strain rate sensitivities (SRSs) for various deformation modes are employed by the model to simulate the strain rate sensitive behaviors under different loading directions and loading rates. Good agreement between the experiments and simulations reveals the importance and necessity of using different SRSs for each deformation mode in hexagonal close-packed metals. Furthermore, the relative activities of each deformation mode and the texture evolution during different loadings are discussed. The anisotropic and strain rate sensitive behavior is ascribed to the various operating deformation modes with different SRSs during loading along different directions.

3D reconstruction and 2D observation were conducted to characterize the microstructure of the castings produced through high pressure die casting with different parameters. Our results indicate that shrinkage pores generally co-existed with externally solidified crystals (ESCs). In specimen produced without fast slow shot speed, big net-shrinkage pores accompanied with ESCs were found in the center of the specimen. When the casting pressurization was introduced, the shrinkage pores gathered to the specimen center and became much less due to the optimization of melt feeding. Much more porosity was found near the gate rather than in the middle of the rod bar, especially gas pores. The filling process simulation reveals that the middle position of the bars was firstly filled and followed by the near gate position accompanied with one intense turbulent flow.

The uniaxial ratchetting-fatigue interaction of extruded AZ31 magnesium (Mg) alloy is investigated by uniaxial stress-controlled cyclic tests at room temperature and with addressing the roles of different plastic deformation mechanisms. Different stress levels are prescribed to reflect the cyclic plasticity of the alloy controlled by diverse deformation mechanisms (i.e., dislocation slipping, deformation twinning and detwinning ones), and then the influences of stress level and stress rate on the ratchetting and fatigue life are discussed. The experimental results demonstrate that different evolution characteristics of whole-life ratchetting and fatigue life presented during cyclic tests with various mean stresses, stress amplitudes and stress rates are determined by the dominated plastic deformation mechanisms. It's worth noting that the ratchetting can occur in the compressive direction even in the cyclic tests with a positive (tensile) mean stress, and the fatigue life increases first and then decreases with the increase of mean stress on account of the interaction between dislocation slipping and twinning/detwinning mechanisms. Comparing the fatigue lives obtained in the asymmetric stress-controlled and symmetrical strain-controlled cycle tests, it is seen that the ratchetting deformation causes an additional damage, and then leads to a shortening of fatigue life.

Additive manufacturing (AM) of Mg alloys has become a promising strategy for producing complex structures, but the corrosion performance of AM Mg components remains unexploited. In this study, wire and arc additive manufacturing (WAAM) was employed to produce single AZ31 layer. The results revealed that the WAAM AZ31 was characterized by significant grain refinement with non-textured crystallographic orientation, similar phase composition and stabilized corrosion performance comparing to the cast AZ31. These varied corrosion behaviors were principally ascribed to the size of grain, where cast AZ31 and WAAM AZ31 were featured by micro galvanic corrosion and intergranular corrosion, respectively.

Machines are integral part of industrial concerns and establishments. Tools are the backbone of machinery and vary according to the application they are being put used to as well as the end product required. Tool wear, on a comparative scale, is more predominant factor in cutting applications. This may be attributed towards a number of factors such as the high temperature arising at the cutting junction, frictional forces being generated; feed rate etc. Conventional methods utilize various alternatives such as lubricants in the form of grease, oil etc. and specially designed cooling fluids. In spite of their beneficial functions, they tend to provide health hazard due to consequent environmental pollution. By using minimum quantity lubrication system, it saves 50% of coolant which done for machining and also reduce environmental problems. In silicon carbide nano additive gives least metal removal rate compared with copper oxide and titanium oxide.

In this study, Mg–6.0Zn–3.0Sn–0.5Mn (ZTM630) magnesium alloy was pre-activated by colloidal Ti, oxalic acid, and phosphoric acid, and a phosphate conversion coating (PCC) was prepared on the alloy surface. The morphology and corrosion resistance of the prepared PCCs were investigated. Surface morphology studies showed that the phosphate crystals that formed the coating were the smallest for the sample pre-activated by phosphoric acid. The coating on the colloidal Ti and the phosphoric acid samples had the largest and the smallest thickness and surface roughness, respectively. The reason for the discrepancy was analyzed by comparing the surface morphologies of alloy samples immediately after the pre-activation treatment and various phosphating treatments. X-ray diffraction analysis revealed that all three PCCs contained the same compounds. The corrosion resistance time from the copper sulfate drop test and the electrochemical data from the potentiodynamic polarization curves showed that the coating pre-activated by phosphoric acid had the best corrosion resistance. Finally, the 1500 h neutral salt spray corrosion test confirmed that the phosphating treated magnesium alloy, which was pre-activated by phosphoric acid, exhibited excellent corrosion resistance and behavior.

Deformation behavior as well as microstructural evolutions of a rolled AZ31 magnesium alloy with and without pre-existing extension twins were studied using compression tests which performed along different orientations at a temperature range of 25–350 °C. The results implied that the initial texture not only influence the evolution of flow stress, but also change the size and fraction of recrystallized grains. In contrast to samples parallel to rolling and transverse directions, compression along normal direction resulted in a respectful softening at 150 °C. The largest size and fraction of new grains at 250 °C were recorded after deformation along rolling direction, while the maximum flow softening was observed during deformation along normal direction. The anisotropy in microstructural evolutions was still retained at 350 °C. Pre-existing twins could reduce the anisotropy of material in respect of flow stress as well as DRX progression, where TD sample showed the lowest DRX fraction at 250 °C. Quaternion misorientation data obtained from EBSD analysis of pretwinned material implied that initial texture could not significantly influence final texture. A different misorientation distribution was realized after deformation of pretwinned material along ND and RD directions.

Photothermal therapy becomes a hotspot in the treatment of bone tumors. Magnesium and its alloys are regarded as potential bone implants for their favorable mechanical property and biodegradable in vivo. However, there is few research devoted to fabricating a photothermal coating on Mg alloy. In the present study, reduced graphene oxide coating with a strong photothermal effect was prepared on the surface of AZ31 via two steps. Firstly, graphene oxide coating was deposited on the surface via electrophoresis deposited (GO#), followed by a reduction process of the graphene oxide coating in ultrapure water (rGO#). GO# and rGO# coatings were characterized by SEM, Raman, XRD, FTIR, and XPS. The results revealed that, compared with GO# coating, the content of oxygen-containing (C O/C O-C, C=O, O C=O) groups on rGO# coating was significantly decreased. rGO# coating was found tightly adhered to AZ31 substrate. According to the first-principles calculations, the well-bonded heterostructure between MgO and rGO is the main reason for the strong bonding force. Moreover, the prepared rGO# coating showed a superior photothermal effect, which brings a new strategy to the treatment of bone tumors with Mg-based implants.

This study investigated dry sliding wear properties of AZ31 magnesium alloy and B4C-reinforced AZ31 composites containing 5, 10, and 20 wt.% B4C with bimodal sizes under different loadings (10–80 N) at various sliding speeds (0.1–1 m/s) via the pin-on-disc configuration. Microhardness evaluations showed that when the distribution of B4C particles was uniform the hardness of the composites increased by enhancing the reinforcement content. The unreinforced alloy and the composite samples were examined to determine the wear mechanism maps and identify the dominant wear mechanisms in each wear condition and reinforcement content. For this purpose, wear rates and friction coefficients were recorded during the wear tests and worn surfaces were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry analyses. The determined wear mechanisms were abrasion, oxidation, delamination, adhesion, and plastic deformation as a result of thermal softening and melting. The wear evaluations revealed that the composites containing 5 and 10 wt.% B4C had a significantly higher wear resistance in all the conditions. However, 20 wt.% B4C/AZ31 composite had a lower resistance at high sliding speeds (0.5–1 m/s) and high loadings (40–80 N) in comparison with the unreinforced alloy. The highest wear resistance was obtained at high sliding speeds and low loadings with the domination of oxidative wear.

Corrosion behavior of AZ31 magnesium alloy in NH4+-bearing chloride solution with controlled pH was investigated by weight loss experiment, hydrogen collection, and electrochemical test combined with surface morphology and topography observation. The results show that NH4+ and pH of the solution can affect the corrosion of AZ31 magnesium alloy. The existence of NH4+ affects the formation and dissolution of corrosion products, which makes the protective effect of the corrosion product layer weaker. The change of pH value not only affects the corrosion mechanism of AZ31, but also alters the concentration of NH4+ ions in the solution, which further influences the corrosion product layer of AZ31, and finally makes the corrosion of AZ31 change significantly.

The laser welding (LW) process of highly reflective materials presents low thermal efficiency and poor stability. To solve the problem, the effects of subatmospheric environment on LW process, technological parameters in subatmospheric environment on weld formation and welding with sinusoidal modulation of laser power on the stability of LW process in subatmospheric environment were explored. The AZ31 magnesium (Mg) alloy was used as the test materials. The test result revealed that the weld penetration in subatmospheric environment can increase by more than ten times compared with that under normal pressure. After the keyhole depth greatly rises, significantly periodic local bulge is observed on the backwall surface of the keyhole and the position of the bulge shifts along the direction of the keyhole depth. Eventually, the hump-shaped surface morphology of the welded seam is formed; moreover, the weld width in local zones in the lower part of the welded seam remarkably grows. During LW in subatmospheric environment, the weld penetration can be further greatly increased through power modulation. Besides, power modulation can inhibit the occurrence of bulges in local zones on the backwall of the keyhole during LW in subatmospheric environment, thus further curbing the significant growth of the weld widths of hump-shaped welding beads and local zones in the lower part of welded seams. Finally, the mechanism of synchronously improving the thermal efficiency and stability of LW process of highly reflective materials through power modulation in subatmospheric environment was illustrated. This was conducted according to theoretical analysis of recoil pressure and observation results of dynamic behaviors of laser induced plasma clouds and keyholes in the molten pool through high speed photography.

Multi-functionalization is the future development direction for protective coatings on metal surface, but has not yet been explored a lot. The effective integration of multiple functions into one material remains a huge challenge. Herein, a superhydrophobic multilayer coating integrated with multidimensional organic-inorganic components is designed on magnesium alloy via one-step plasma-induced thermal field assisted crosslinking deposition (PTCD) processing followed by after-thermal modification. Hard porous MgO ceramic layer and polytetrafluoroethylene (PTFE) nano-particles work as the bottom layer skeleton and filler components separately, forming an organic-inorganic multilayer structure, in which organic nano-particles can be crosslinked and cured to form a compact polymer-like outer layer with hierarchical surface textures. Remarkably, the chemical robustness after prolonged exposure to aqua regia, strong base and simulated seawater solution profits from polymer-like nanocomposite layer uniformly and compactly across the film bulk. Moreover, the self-similar multilayer structure coating endows it attractive functions of strong mechanical robustness (>100th cyclic rotary abrasion), stable and ultra-low friction coefficient (about 0.084), high-temperature endurance, and robust self-cleaning. The organic-inorganic multilayer coating also exhibits high insulating property with breakdown voltage of 1351.8 ± 42.4 V, dielectric strength of 21.4 ± 0.7 V/µm and resistivity of 3.2 × 1010 Ω·cm. The excellent multifunction benefits from ceramic bottom skeleton, the assembly and deposition of multidimensional nano-particles, and the synergistic effect of organic inorganic components. This study paves the way for designing next generation protective coating on magnesium alloy with great potential for multifunctional applications.

In the preparation of plasma electrolytic oxidation (PEO) coating, the rapid heating of freely-happened electron avalanche under traditional discharge (TD) mode inevitably results in a strong eruption of electric breakdown melt. The PEO coating is loose and invariably composed of a very thin inner dense layer and an outer loose layer, as a result of which its properties and application have been limited greatly. In this work, for purpose of weakening the eruption of breakdown melt, thickening the inner dense layer, densifying the outer loose layer and improving the performance of PEO coating, ordinal discharge (OD) mode of PEO coating is developed by regulating the mass ratio of MgF2 to MgO (α) and voltage in the PEO investigation on AZ61 magnesium alloy in KF-KOH electrolyte. The formation mechanism under different discharge mode, electrochemical corrosion and wear of PEO coatings are investigated. The results show that the suitable α and voltage for effective OD are 1.3 and 130 V under which the freely-happened electron avalanche in MgF2 under TD mode can be restricted by the adequate adjacent MgO. Compared with TD mode, the inner dense layer, in which the ( 1 ¯ 0 1 ¯ ) plane of MgF2 is parallel to the (111) plane of MgO at their well-knit semi-coherent interface, is thickened to 2.4∼7.2 times, the corrosion potential (Ecorr) improvement is enlarged to 3.6∼13.2 times and the corrosion current intensity (Icorr) is reduced from 10.8∼9.499 to 0.433 (10−6 A/cm2). The outer loose layer is densified and the wear rate is lessened 65.5%∼89.8% by the evident melioration in surface porosity, impedance and hardness. This work deepens the understanding about the discharge of PEO coating and provides an available OD mode for preparing excellent PEO coating.

The relationship among the microstructure, hardness and electrical conductivity of the as-forged ZYK530 Mg alloy after heat treatment was analyzed and studied using a microscope, X-Ray Diffractometer, eddy current conductivity meter, and Vickers microhardness tester, to explore optimum heat treatment process of ZYK530 Mg alloy. The results show that: with the prolongation of holding time, the electrical conductivity and microhardness show the same change trend, both of which show an oscillatory upward trend, and then decrease in an oscillatory downward trend after reaching the peak value. There is a linear positive correlation between the conductivity and the hardness, and the fitting results of the conductivity and hardness are in good agreement with the measured results; combined with the actual production, when the heat-treatment is 480 ℃ × 8 h + 220 ℃ × 3 h, the highest hardness is 79.2 HV, the electroconductivity is 36.2%IACS, and the comprehensive performance is the best, which is the best heat treatment process.

An ideal fixation system for guided bone (GBR) regeneration in oral surgery must fulfil several criteria that includes the provision of adequate mechanical fixation, complete resorption when no longer needed, complete replacement by bone, as well as be biocompatible and have a good clinical manageability. For the first time, a biodegradable magnesium fixation screw made of the magnesium alloy WZM211 with a MgF2 coating has been designed and tested to fulfill these criteria. Adequate mechanical fixation was shown for the magnesium fixation screw in several benchtop tests that directly compared the magnesium fixation screw with an equivalent polymeric resorbable device. Results demonstrated slightly superior mechanical properties of the magnesium device in comparison to the polymeric device even after 4 weeks of degradation. Biocompatibility of the magnesium fixation screw was demonstrated in several in vitro and in vivo tests. Degradation of the magnesium screw was investigated in in vitro and in vivo tests, where it was found that the screw is resorbed slowly and completely after 52 weeks, providing adequate fixation in the early critical healing phase. Overall, the magnesium fixation screw demonstrates all of the key properties required for an ideal fixation screw of membranes used in guided bone regeneration (GBR) surgeries.

To suppress the edge crack of the magnesium alloy sheet during the ordinary rolling process, a new rolling process named width-limited rolling was proposed in this paper. Width-limited rolling is a rolling method in which the width of the alloy sheet is limited by modifying the shape of the rollers, allowing a compressive stress field to form at the edge portion of the alloy sheet during rolling, resulting in the reduction of edge cracks. At present work, magnesium alloy sheets were separately subjected to ordinary rolling and width-limited rolling. The microstructure evolution and mechanical properties of the rolled sheets were investigated by EBSD, TEM, and XRD. The results exhibited that under the same rolling conditions, the sheet after ordinary rolling exhibited obvious edge cracks while no crack was found at the edge of the sheet after width-limited rolling. The edge crack suppressing effect was attributed to the reduction of the tensile stress along rolling direction during WLR, promoting the synchronous extension of the edge and center regions to suppress edge crack tendency. Microstructure observation showed that the compressive twins formed in the sheet after ordinary rolling usually exhibited as thin plates and cannot continue to fully develop due to the premature generation of the edge cracks. However, the compressive twins developed maturely in some of which double twins formed and various slip systems with different dislocation Burgers vectors occurred in the rolled sheet after WLR. More twin intersections and shear bands, providing more potential recrystallization nucleation sites, which are beneficial to weaken basal texture. With the cooperation of twinning and dislocation slip, the texture of the sheet after the width-limited rolling is weakened and the mechanical properties are improved.

Al-based MIL-53 MOF nanostructure was synthesized hydrothermally and then co-deposited in the electroless nickel coating on AM60B magnesium alloy using Zr pretreatment as an eco-friendly underlayer. The MIL-53(Al) nanostructure was synthesized in the form of layered semi-cube crystals with the surface area and mean pore diameter of 985.72 m2g−1 and 2.00 nm, respectively. The SEM images captured with two various zooming scales from the surface of the plain and MOF containing electroless layers showed cauliflower-like morphology with even distribution of nodule size. Also, the sub-grains of the plain coating disappeared after incorporation of the MOF. Although, both the normal and nanostructure-containing electroless layers have crystalline-amorphous structure, but the nanocomposite coating showed less crystallinity. The average surface roughness of the plain electroless coating was about 309 nm, which decreased to about 222 nm after incorporation of the MOF. The XRD patterns showed that the characteristic peak of Ni broadened after incorporation of the MOF, probably due to the decreasing of the crystallinity. For the heat-treated normal and MOF containing coatings at 200 °C no phase transition takes place, but new peaks appeared for heat-treated coatings at 400 °C due to the crystallization and second-phase precipitation. The results of the EIS tests showed an increase in the amount of the charge transfer resistance (from 19 to 29 kΩ cm2) after addition of the MOF, which means an improvement in the corrosion resistance. Also, low Jcorr of the composite coating represents its higher corrosion resistance with respect to the plain coating. The micro-hardness values of the composite coating before and after the heat treatment were higher than the plain coating. Also, the Ni-P-MOF coating has a lower wear rate both before and after the heat treatment due to an improvement in its micro-hardness.

Specific gravity segregation that occurs during the smelting process always leads to the low composition homogeneity and poor performance stability of the magnesium-rare earth (Mg-RE) alloys. In this study, the segregation behavior of Mg-Gd alloy was investigated by sampling from different locations in the ingot fabricated by a resistance furnace without a pouring process. The combined application of induction-heating and mechanical stirring with various speeds (0–130 r/min) was applied to promote the distribution homogeneity of Gd atoms. In the resistance-heating fabricated ingot, Gd content at the bottom section reaches 407% of that at the top. The coarse dendrites surrounded by the network-like eutectic structures are responsible for the brittle fracture with a poor elongation of 3.7%. By the combined employment of the induction heating and mechanical stirring with the speed of 87 r/min at 740 °C for 40 s, the variation of the Gd content within the whole ingot can be reduced to be the minimum of 0.23 wt%. Corresponding formation and regulating models of segregation were also proposed. However, the cooling rate of the melt is reduced by the continuous increase of the stirring speed to 130 r/min, which results in the grain coarsening and lower homogeneity of the ingot.

Abstrct Polycaprolactone/hydroxyapatite (PCL/HA) composite coating was fabricated by a combination of hydrothermal and dipping methods to delay the degradation of Mg alloy AZ31 as bioresorbable materials. The PCL/HA coating was composed of nano rod-shape HA crystals and PCL filled in the space of HA crystals. Compared with the single HA coating, the binding strength between the PCL/HA composite coating and Mg alloy was obviously improved and the PCL/HA coating still adhered to the surface of AZ31 substrate even after 38 days of immersion. The electrochemical corrosion rate of HA coated sample was reduced by ten times after being filled by PCL. The electrochemical impedance spectroscopy (EIS) and immersion test results showed that the PCL/HA composite coating could provide a more effective barrier for Mg substrate than the HA coating alone. The cytocompatibility and the antibacterial property of HA coating and PCL/HA coating were evaluated by culturing with bone marrow-derived mesenchymal stem cells (BMSCs) and methicillin-resistant staphylococcus aureus (MRSA) for 24 h under direct culture conditions, respectively. The PCL/HA composite coating showed better BMSC cell compatibility, more suitable for BMSC adhesion than HA coating alone and showed a potential application prospect as a biological materials. However, from the perspective of clinical applications, the antibacterial property of PCL/HA composite coating needs to be further improved.

To maximize the benefits of wire arc additive manufacturing (WAAM) processes, the effect of post-deposition heat treatment on the microstructure and mechanical properties of WAAM AZ80M magnesium (Mg) alloy was investigated. Three different heat treatment procedures (T4, T5 and T6) were performed. According to the results, after T4 heat treatment, the microsegregation of alloying elements was improved with the eutectic structure dissolved. Samples after T5 heat treatment inherited the net-like distribution of secondary phases similar to the as-deposited sample, where the eutectic structure covering the interdendritic regions and the β-phase precipitated around the eutectic structure. After T6 heat treatment, the tiny β-phases re-precipitated from the matrix and distributed in inner and outer of the grains. The hardness distribution of the samples went through T4 and T6 heat treatment was more uniform in comparison to that of T5 heat treated samples. The tensile test showed that the T6 heat treatment improved the strength and ductility, and the anisotropy between horizontal and vertical can be eliminated. Moreover, T4 treated samples exhibited highest ductility.

The relationship between activities of involved deformation mechanisms and the evolution of microstructure and texture during uniaxial tension of AZ31 magnesium alloy with a rare non-basal texture has been thoroughly investigated in the present study by means of electron backscattered diffraction (EBSD) measurement and visco-plastic self-consistent (VPSC) modeling. These results show that except basal slip and prismatic slip, { 10 1 ¯ 2 } extension twin (ET) also plays a significant role during plastic deformation. With the increasing tilted angle between loading direction and rolling direction (RD) of sheet, the activity of { 10 1 ¯ 2 } ET possesses a decreasing tendency and its role in plastic deformation changes from the one mainly sustaining plastic strain to the one mainly accommodating local strain between individual grains. When { 10 1 ¯ 2 } ET serves as a carrier of plastic strain, it mainly results in the formation of basal texture component (c-axis//ND, normal direction). By comparison, when the role of { 10 1 ¯ 2 } ET is to accommodate local strain, it mainly brings about the formation of prismatic texture component (c-axis//TD, transverse direction). At large plastic deformation, the competition between basal slip and pyramidal slip is responsible for the concentration of tilted basal poles towards ND within all deformed samples. The larger difference is between the activities of basal slip and pyramidal slip, the smaller separation is between these two tilted basal poles. Besides, VPSC modeling overestimates volume fractions of { 10 1 ¯ 2 } ET in samples with angle of 0 to 30° between loading direction and RD of sheet because interactions between twin variants are not included in VPSC modeling procedure at the present form. In addition, as compatible deformation between individual grains cannot be considered in VPSC modeling, the predicted volume fractions of { 10 1 ¯ 2 } ET in samples with angle of 45 to 90° between loading direction and RD of sheet are smaller than the correspondingly measured results.

A comparative evaluation of conventional drilling and helical milling to process holes in AZ31 Magnesium alloy is reported. The results highlight the advantages of helical hole milling over the mechanical drilling process in terms of lower machining forces. Besides, the process is successful in reducing the machining temperature and size of the burrs formed, in addition to improved surface finish. Further, analysis of the helical hole milling process demonstrated that the axial pitch has a dominating influence on the thrust force, whereas the feed value greatly influences the radial force. The spindle speed is found to influence the machining temperature significantly. The chip morphology is found to be dependent on feed and axial pitch, with the feed value influencing the chip segmentation and breakability. The absence of burn marks on the chip surface indicates a lower risk of fire hazard.

Both a conventional flow distributer and an improved one with a flow buffer were applied respectively during the high pressure die casting (HPDC) process, and samples of AZ91D magnesium alloy with different microstructure mainly consisting of α-Mg grains, β-phase and porosities were obtained. According to the grain orientation analysis, the predominant deformation behavior in α-Mg grains was dislocation slip, supplemented by deformation twinning. Dislocation slip was more difficult to occur in the samples with the improved flow distributer on account of the fact that the size of α-Mg grains in the microstructure was finer and more uniform. During the in situ tensile deformation test, cracks were observed to initiate from gas-shrinkage pore and island-shrinkage, and two main crack propagation mechanisms, porosity growth and coalescence were found accordingly. When the crack was in contact with the β-phase, it would pass through and fracture the network β-phase, whereas bypass the island β-phase by detaching it from the surrounding α-Mg grains. Mechanical property tests showed that the samples with relatively more homogeneous microstructure would perform higher mechanical properties, which was the combined effect of matrix α-Mg grains, β-phase, and porosities.

The introduction of biodegradable implant materials has significantly improved the postoperative subjective feelings of patients within the past few decades, among which magnesium alloy is widely considered a favorable choice as its appropriate biodegradability and evident antibacterial activity. Here, we reveal a semisolid rheo-formed Mg–Zn–Sr alloy ureteral implant that displayed suitable degradability and biocompatibility in a pig model. Refined non-dendritic microstructure was observed in the rheo-formed alloy, which led to ca. 47% increase in ultimate tensile strength (from 195.0 MPa to 288.1 MPa) and more homogeneous degradation process compared with the untreated alloy. No post-interventional inflammation or pathological changes of the test animals were observed during the implantation period, and the corrosion rate (0.22 ± 0.04 mm·y−1) perfectly fitted the clinical ureteral stent indwelling time. The urine bacteria numbers decreased from 88 ± 13 CFU·mL−1 at 7 weeks post operation to 59 ± 8 CFU·mL−1 at 14 weeks post operation, which confirmed the evident antibacterial activity of the alloy. Our study demonstrates that the Mg–Zn–Sr alloy is clinically safe for urinary system, enabling its efficacious use as ureteral implant materials.

A magnesium alloy containing essential, non-toxic, biodegradable elements such as Ca and Zn has been fabricated using a novel twin-roll casting process (TRC). Microstructure, mechanical properties, in vivo corrosion and biocompatibility have been assessed and compared to the properties of the rare earth (RE) element containing WE43 alloy. TRC Mg-0.5 wt% Zn- 0.5 wt% Ca exhibited fine grains with an average grain size ranging from 70 to 150 μm. Mechanical properties of a TRC Mg-0.5Zn-0.5Ca alloy showed an ultimate tensile strength of 220 MPa and ductility of 9.3%. The TRC Mg-0.5Zn-0.5Ca alloy showed a degradation rate of 0.51 ± 0.07 mm/y similar to that of the WE43 alloy (0.47 ± 0.09 mm/y) in the rat model after 1 week of implantation. By week 4 the biodegradation rates of both alloys studied were lowered and stabilized with fewer gas pockets around the implant. The histological analysis shows that both WE43 and TRC Mg-0.5Zn-0.5Ca alloy triggered comparable tissue healing responses at respective times of implantation. The presence of more organized scarring tissue around the TRC Mg-0.5Zn-0.5Ca alloys suggests that the biodegradation of the RE-free alloy may be more conducive to the tissue proliferation and remodelling process., Graphical abstract Image 1, Highlights • Mg-0.5Zn-0.5Ca alloy plates were fabricated by a twin-roll casting (TRC) process. • TRC alloy showed an ultimate strength and elongation of 221 ± 2 MPa and 9 ± 2%. • Gas development during in vivo degradation was analysed using μ-CT techniques. • Histological analysis revealed a good biocompatibility and promoted healing.

This work produced a MgAl-layered double hydroxide by hydrothermal treatment of a plasma electrolytic oxidation (PEO) coating on magnesium alloy AZ31 in an phosphate electrolyte, followed by an ion-exchange reaction in 0.1 M phosphate solution. The coated specimens were scratched. Characterization, including utilization of the localized technique SIET, measured the pH and pMg distributions and optical morphologies around the artificial defects during immersion in 0.05 M NaCl solution. In contrast with phosphate loaded PEO/LDHs, a stronger alkalinization area (with pH 11.4∼12.3) appeared in the passive PEO specimens. Due to formation of insoluble Mg(OH)2 products, the pMg map showed depletion of Mg2+ in this high pH area. Combined with optical morphologies and SEM images, the better self-healing ability toward defects for phosphate loaded PEO/LDHs was confirmed.

A composite coating of nitrogen-doped carbon dots (N CDs) and polydopamine (PDA) was prepared on magnesium alloy by combining electrodeposition with dip coating methods. The microstructure of the N CDs/PDA composite coating, including composition, surface morphology, and crystalline structure, is characterized by Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy, respectively. The corrosion protection performances of the composite coating are evaluated by potentiodynamic polarization tests, electrochemical impedance spectroscopy, and salt spray tests. The effect of the particle size of the N CDs on the corrosion performance is also investigated. The results show that the corrosion performance of the N CDs coatings are enhanced with the increase of the particle sizes. Furthermore, an obvious self-healing performance is observed on the surface of the N CDs/PDA composite coating. These results indicate that N CDs/PDA composite coating can improve the corrosion performance of the Mg alloy, and open a new design direction for the protective coating of metallic materials.

Friction self-piercing riveting (F-SPR) process based on a pip die has been invented to solve the cracking problems in riveting high-strength and low-ductility light metals, such as magnesium alloys, cast aluminum, and 7 series aluminum alloys. In this paper, in order to solve quality issues caused by the misalignment between rivet and pip-die in F-SPR, a flat-die based F-SPR process was proposed and employed to join 1.27 mm-thick AA6061-T6 to 3 mm-thick AZ31B. The results indicate that a 1.0 mm die distance is effective to avoid rivet upset and insufficient flaring. As the feed rate increases, the heat input in the whole process decreases, resulting in a larger riveting force, which in turn increases both the bottom thickness and interlock amount. Besides, solid-state bonding, including Al-Mg intermetallic compounds (IMCs), Al-Mg mechanical mixture, and Al-Fe atom interdiffusion was observed at the joint interfaces. The upper Al layer was softened, but the lower Mg layer was hardened, and both sheets exhibited a narrowed affected region with the increase of feed rate, while the rivet hardness shows no obvious change. Three fracture modes appeared accompanying the variations in lap-shear strength and energy absorption as the feed rate increased from 2 mm/s to 8 mm/s. Finally, the F-SPR process using a flat die was compared to those using a pip die and a flat bottom die to show the advantage of flat die on coping with the misalignment problem.

Split Hopkinson pressure bar (SHPB) tests were conducted on pre-rolled AZ31 magnesium alloy at 150–350 ℃ with strain rates of 2150s-1, 3430s-1 and 4160s-1. The mechanical response, microstructural evolution and accommodation mechanism of the pre-rolled AZ31 magnesium alloy under high-speed impact loading were investigated. The twin and shear band are prevailing at low temperature, and the coexistence of twins and recrystallized grains is the dominant microstructure at medium temperature, while at high temperature, dynamic recrystallization (DRX) is almost complete. The increment of temperature reduces the critical condition difference between twinning and DRX, and the recrystallized temperature decreases with increasing strain rate. The mechanical response is related to the competition among the shear band strengthen, the twin strengthen and the fine grain strengthen and determined by the prevailing grain structure. The fine grain strengthen could compensate soften caused by the temperature increase and the reduction of twin and shear band. During high-speed deformation, different twin variants, introduced by pre-rolling, induce different deformation mechanism to accommodate plastic deformation and are in favor for non-basal slip. At low temperature, the high-speed deformation is achieved by twinning, dislocation slip and the following deformation shear band at different deformation stages. At high temperature, the high-speed deformation is realized by twinning and dislocation slip of early deformation stage, transition shear band of medium deformation stage and DRX of final deformation stage.

Twinning and detwinning behavior, together with slip behavior, are studied in a textured AZ31 magnesium alloy under compressive and tensile strains along the rolling direction (RD) after each interrupted mechanical test via quasi in-situ electron backscattered diffraction technique. The results show that twinning firstly takes place under the compressive strain along the RD. With the increasing compressive strain, { 10 1 ¯ 2 } tensile twins firstly nucleate, then propagate, and finally thicken. While under a reversed tensile strain along the RD, detwinning occurs. No nucleation happens during detwinning. Thus, tensile twins can detwin at lower tensile strain, followed by thinning, shortening, and vanishing. Slips are also activated to accommodate the plastic deformation. In the matrix, prismatic slip can only dominate at relatively high strains. Otherwise, basal slip dominates. While in the twins, prismatic slip can activate at lower strains, which is ascribed to the texture reorientation.

Poor ductility is the primary concern of magnesium matrix composites (MMCs) inflicted by non-deformable ceramic particle reinforcements. Metal particles which melt at elevated temperature can be used as reinforcement to improve the deformation characteristics. Ti-6Al-4V particles reinforced AZ31 MMCs were produced through friction stir processing (FSP) which was carried out in a traditional vertical milling machine. The microstructural features as well as the response to external tensile load were explored. A homogenous distribution of Ti-6Al-4V was achieved at every part of the stir zone. There was no chemical decomposition of Ti-6Al-4V. Further, Ti-6Al-4V did not react with Al and Zn present in AZ31 alloy to form new compounds. A continuous strong interface was obtained around Ti-6Al-4V particle with the matrix. Ti-6Al-4V particles underwent breakage during processing due to severe plastic strain. There was a remarkable refinement of grains in the composite caused by dynamic recrystallization in addition to the pinning of smaller size broken particles. Dense dislocations were observed in the matrix because of plastic deformation and the associated strain misfit. Ti-6Al-4V particles improved the tensile behavior and assisted to obtain appreciable deformation before fracture. Brittle mode of failure was avoided.

The rapid degradation of Mg alloy was reduced by incorporating titanate on a fluorine-based anodized layer. The coating shows (i) excellent biomineralization ability, (ii) improved local and periodical corrosion behavior and (iii) enhanced expression of osteogenic factors (Runx2, Col 1, OCN and OPN) along with (iv) the antibacterial property. The fluoride and magnesium ions dissolution from the anodized layer is responsible for the better expression of osteogenic factors and antibacterial behavior. The preparation of the titanate incorporated anodized Mg alloy (Ti-AMg) is a facile solution to overcome the implant-associated bacterial infections with required biological functions including progression of bone ingrowth and biocompatibility.

This paper presents a method of the formation of composite polymer-containing coatings on a Mg–Mn–Ce magnesium alloy by forming a ceramic-like layer using plasma electrolytic oxidation (PEO) and subsequent spraying superdispersed polytetrafluoroethylene suspension. The coating composition and their morphological features were studied by SEM, EDS, GDOES, and XRD. The presented data confirm the embedding of fluoropolymer in the PEO coating. The evaluation of the corrosion properties of the formed composite polymer-containing coatings indicates a decrease in the corrosion current density by more than 3 orders of magnitude in comparison with the base PEO coating. The incorporation of a fluoropolymer in a PEO layer by more than 32% increases the load value at which abrasion of the coating to the substrate occurs and reduces the wear of the coating by more than 27 fold in comparison with the PEO layer. It has been established that composite coatings possess hydrophobic properties: the value of the contact angle attains 152 °.

Surface properties play a significant role in the biocompatibility and biodegradation of Mg-alloy implants which primarily depends on the manufacturing route followed. In the present work, the milling process has been optimized on ZM21 Mg-alloy to obtain the trade-off between the material removal rate (MRR), surface roughness (SR), and degradation rate (DR). Milling parameters vary the amount of force and pressure developed between the tool and work interface, thus, affecting the MRR and SR. The weight loss of machined samples was measured after seven days of immersion in simulated body fluid (SBF) to calculate the DR. L16 orthogonal array was used to study the effect of milling parameters such as tool rotation speed (TRS), feed rate (FR), and depth of cut (DoC). The result showed that the variation in the values of milling parameters significantly influences the surface integrity of Mg-alloy, thus affecting the DR. Chip morphology and surface cracks with scanning electron microscopy (SEM) were evaluated to correlate the influence of milling parameters on the machining performance of ZM21 Mg-alloy. The machined surface of Mg-alloy must be of very low SR and cracks-free to avoid fast corrosion. Therefore, grey relational analysis (GRA) has been employed for multi-optimization to get the best trade-off for higher MRR and lower SR and DR. The optimized setting suggested by GRA for milling of ZM21 Mg alloy is TRS; 2700RPM, FR; 25mm/min, and DoC; 1.25mm.

Wet etching is a micromachining process in which a material is immersed in liquid chemicals or etchants to remove unwanted sections from the surface. The process is generally known as cost-effective, reliable and suitable for high-production environments. Magnesium alloys are presenting a strong popularity in recent years since it is one of the lightest engineering alloys. Hence, the micromachining of these materials is becoming an important research area. One of the promising methods is wet etching. In this experimental study, two different concentrations (10 and 20 ml) of a nitric acid solution are used at room temperature. The wet etching characteristics of a selected magnesium alloy is determined by analysing the thickness reduction and surface roughness as well as colour degradation on the machined surfaces.

Ultrasonic fatigue tests are performed on a magnesium alloy with and without ultrasonic peening treatment (UPT). Surface enhancement layer leads to the complete change of crack initiation sites. However, crack initiation mechanism keeps the same and results in a single-faceted morphology at crack initiation site. Microcracks initiate as Mode II crack within the original grain, but deflect to Mode I crack outside of the original cracked grain. A threshold SIF value is proposed to evaluate the retarding effect of grain boundary on microcrack propagation. Outside of the original cracked grain, Mode I crack propagation below the threshold ΔKσ-th is responsible for the formation of fine granular area (FGA, a nanograin layer). Based on the Numerous Cyclic Pressing (NCP) model, it is proposed that crack type should be another necessary condition for the formation of FGA.

The preparation of pH-responsive nanocontainers by typical silane modification of the mesoporous silica nanoparticle (MSN) surface is usually high-cost, complex, and time-consuming, which remains a great challenge for effective corrosion protection of magnesium alloy. Here, a new strategy to construct pH-responsive nanocontainers (MSN-MBT@LDH) is demonstrated. The nanocontainers consist of corrosion inhibitor (2-mercaptobenzothiazole, MBT) loaded MSN core and layered double hydroxide (LDH) nanosheet shell serving as gatekeepers. The successful loading of MBT and encapsulation by LDH nanosheets were confirmed by a series of characterization such as scanning transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (STEM-EDS) and N2 adsorption/desorption isotherms. The pH-responsive feature of the nanocontainers was demonstrated by determination of the MBT concentration in buffer solutions with different pH values. A smart corrosion protection system on Mg alloy is obtained by incorporating the synthesized nanocontainers into a self-assembled nanophase particle (SNAP) coating. The electrochemical tests and visual observations show that the hybrid coating has the best barrier properties and robustness in corrosion protection in NaCl corrosive solutions in comparison with the control coatings. The present method simplifies the synthesis processes of nanocontainers and eliminates the potential detrimental effect of excess gatekeepers on the coating. The findings provide new insights into the preparation of scalable nanocontainers. The self-healing coatings are expected to have widespread applications for corrosion protection of Mg alloy and other metals.

Compared to cold drawing, dieless drawing has shown great potential for manufacturing biodegradable Mg alloy microtubes due to the large reduction in area acquired in a single pass. However, owing to the local heating and local deformation, the deformation mechanism during dieless drawing is not clear, and thus causing difficulties in controlling the microstructure of dieless drawn tubes. For the purpose of acquiring a desired microstructure, in this study the deformation mechanism of ZM21 Mg alloy tube was clarified by conducting continuous observation of the microstructural evolution during dieless drawing. The results show that both SRX and DRX occurred during dieless drawing. SRX occurred before the plastic deformation to soften dieless drawn tubes. With increase of feeding speed, the deformation mechanism changed accordingly: (1) At the low-speed of 0.02 mm/s, the deformation mechanism was dominated by twin-slip sliding, during which {10–12} tension twins were generated inside grains to accommodate the plastic deformation by changing the crystal orientation. (2) At the intermediate-speed of 2 mm/s, a twin-DRX process related to {10–12} tension twin was observed, which was characterized by the generation of abundant {10–12} tension twins and the evolution of misorientation angle of {10–12} tension twins. Moreover, the transformation from twin-DRX to CDRX can be observed at the late stage of plastic deformation, which was attributed to the inhomogeneous conditions of dieless drawing. (3) At the high-speed of 5 mm/s, a CDRX process was observed, during which grain boundary sliding and grain tilting were observed, in addition to the gradual rotation of subgrains. These results show that during dieless drawing, DRX is not only a temperature-dependent phenomenon, but also influenced by the variation of feeding speed.

Together with the mechanical properties, the degradation rate is an important factor for biodegradable implants. The ZKX50 Mg alloy is a suitable candidate to be used as a biodegradable implant due to its favorable biocompatibility and mechanical properties. Current research investigates the degradation rate and corrosion behavior of the ZKX50 as a function of the microstructure constituents and their morphology. Since grain refinement is the main strengthening mechanism for the ZKX50, the effect of the microstructure refinement on the corrosion rate was studied by applying electron beam processing (EBP) and friction stir processing (FSP) on the ZKX50 cast alloy. To study the effect of the microstructure constituents and their morphology a subsequent solution heat treatment (HT) was applied to the processed samples. The results show that the EBP and FSP lead to a uniform and remarkably refined microstructure of the ZKX50 alloy and homogeneous distribution of the intermetallic phases. The results of electrochemical corrosion tests together with the microstructure characterization show that microgalvanic corrosion is the predominant mechanism that occurs between the Ca2Mg6Zn3 intermetallic phase and α-Mg matrix. According to the results attained through the electrochemical tests, the EBPed-HT ZKX50 alloy shows higher corrosion resistance compared to all other conditions immersed in 0.5 wt% NaCl solution. The dissolution and spheroidizing of Ca2Mg6Zn3 particles during the solution heat treatment provides higher corrosion resistance mainly by decreasing the microgalvanic corrosion. The microstructure of the heat-treated samples does not show a significant grain coarsening which can degrade the enhancement of the mechanical properties achieved by the EBP and FSP.

In the present research, the dynamic recrystallization (DRX) behavior of a newly-developed Mg–Al–Zn–RE alloy with abundant second-phase particles during hot extrusion is investigated by coupling finite element (FE) and cellular automaton (CA) models. A two-dimensional CA model is developed to quantitatively and topologically evaluate the DRX process during deformation with constant forming conditions. Considering the fact that second-phase particles with various sizes extensively exist in the studied Mg–Al–Zn–RE magnesium alloy, models of DRX nucleation and grain growth velocity are modified. The coefficients of the modified CA model are calibrated by isothermal compression experiments of the magnesium alloy. Subsequently, the CA model is coupled with FE analysis to investigate the DRX behavior during the hot extrusions of the Mg–Al–Zn–RE alloy. The DRX behavior of the magnesium alloy at different stages and positions of extruded plates is simulated by the established model. Finer grains near the edge than in the inner of the plates result from higher strain and strain rate. The influence of extrusion conditions on microstructural evolution is explored. Under the employed forming conditions, average grain size decreases 28–62 times from as-cast and solution-treated to as-extruded state due to grain refinement by DRX. With increasing initial billet temperature or extrusion speed, average grain size increases. The finest grains are obtained at the initial billet temperature of 623 K and the extrusion speed of 7.83 mm/s. Low initial billet temperature or high extrusion speed benefits homogeneous grain distribution. The simulated results are in good agreement with experimental ones.