Increasing Duty Cycle Research Articles

Experimental investigation of a spanwise plasma jet array in a turbulent boundary layer for skin-friction drag reduction

Three different types of particle imaging velocimetry (PIV) measurements, namely planar-PIV, micro-PIV, and stereo-PIV, are integrated to provide a full picture of the interaction between a spanwise plasma jet array and a turbulent boundary layer (TBL) at Reθ = 1208. Quiescent-flow characterization reveals that the plasma actuator array induces a wavy jet. With increasing duty cycle (DC), the peak jet velocity grows yet the height of the jet body decreases. When the TBL is actuated by such a plasma jet array, the spanwise distribution of the relative drag variation exhibits two regions with opposite signs, and the formation of these two regions can be attributed to the upwash and the downwash effects of the plasma-induced vortex, respectively. After spatial-averaging in the plasma actuation zone, net drag reduction (DR = 3.2%) is only achieved at the lowest DC of 10%. Although, by increasing the duty cycle, more drag reduction can be obtained in the upwash zone, the accompanying drag increase in the downwash zone is even prominent.

Self-repairing Al2O3−TiO2 coatings fabricated through plasma electrolytic oxidation with various cathodic pulse parameters

The influence of cathodic pulse parameters was evaluated on plasma electrolytic oxidation (PEO) coatings grown on 7075 aluminum alloy in a silicate-based electrolyte containing potassium titanyl oxalate (PTO) using pulsed bipolar waveforms with various cathodic duty cycles and cathodic current densities. The coatings were characterized by SEM, EDS, and XRD. EIS was applied to investigate the electrochemical properties. It was observed that the increase of cathodic duty cycle and cathodic current density from 20% and 6 A/dm2 to 40% and 12 A/dm2 enhances the growth rate of the inner layer from 0.22 to 0.75 µm/min. Adding PTO into the bath showed a fortifying effect on influence of the cathodic pulse and the mentioned change of cathodic pulse parameters, resulting in an increase of the inner layer growth rate from 0.25 to 1.10 µm/min. Based on EDS analysis, Si and Ti were incorporated dominantly in the upper parts of the coatings. XRD technique merely detected γ-Al2O3, and there were no detectable peaks related to Ti and Si compounds. However, the EIS results confirmed that the incorporation of Ti4+ into alumina changed the electronic properties of the coating. The coatings obtained from the bath containing PTO using the bipolar waveforms with a cathodic duty cycle of 40% and current density values higher than 6 A/dm2 showed highly appropriate electrochemical behavior during 240 d of immersion due to an efficient repairing mechanism. Regarding the effects of studied parameters on the coating properties, the roles of cathodic pulse parameters and PTO in the PEO process were highlighted.

Statistical modeling and optimization of clad geometry in laser cladding of Amdry 365 on Hastelloy X superalloy with response surface methodology

The aim of this study is to statistically investigate and optimize the laser cladding process of Hastelloy X superalloy using NiCoCrAlY powder (Amdry 365). In this study, response surface methodology was used to investigate the influence of laser input variables such as scanning velocity, laser power, and duty cycle on the clad geometry (including height, width, and angle) and dilution ratio. The results indicate that with increasing duty cycle and laser power, the clad width increases significantly, while the clad height increases slowly. However, increasing the scanning velocity leads to a decrease in the width and height of the clad. Furthermore, the clad angle and dilution ratio increase with increasing input parameters. The results of variance analysis shows that laser scanning velocity had the most significant impact on clad height, angle and dilution ratio, while laser power had the greatest influence on clad width. The laser power of 321.3 W, the scanning velocity of 6.3 mm/s and the duty cycle of 76 % proved to be the optimal input parameters. An experimental test was carried out to validate the optimal conditions based on the optimization responses. The validation results show that the developed models are able to describe the responses with an accuracy of less than 9 % error. The EDS analysis performed in the cladding zone of the optimum specimen showed the presence of the β phase in the dendritic region and the γ phase in the interdendritic region.

Influence of Current Duty Cycle and Voltage of Micro-Arc Oxidation on the Microstructure and Composition of Calcium Phosphate Coating

The micro-arc oxidation (MAO) technique was employed to produce calcium phosphate coatings on titanium surfaces using an electrolyte composed of hydroxyapatite and calcium carbonate in an aqueous solution of orthophosphoric acid. The coatings’ morphology and composition were regulated by adjusting electrical parameters, specifically the duty cycle and voltage. This study examined the effects of the duty cycle and voltage during the MAO process on the microstructure and composition of calcium phosphate coatings on VT1–0 titanium substrates. Scanning electron microscopy (SEM) was utilized to analyze the microstructure and thickness of the coatings, while X-ray diffraction (XRD) was employed to determine their phase composition. The findings reveal that the surface morphology of the calcium phosphate coatings transitions from a porous, sponge-like structure to flower-like formations as the duty cycle and voltage increase. A linear increase in the voltage within the applied duty cycles led to a rise in the size of the forming particles of amorphous/crystalline structures containing phases of monetite (CaPO3(OH)), monocalcium phosphate monohydrate (Ca(H2PO4)2·H2O), and calcium pyrophosphate (γ–Ca2P2O7).

Pulsed heating of the self-actuated cantilever: a one-dimensional exact solution investigation of non-axial temperature gradients

Self-actuated bimorph cantilevers are implemented in a variety of micro-electro-mechanical systems. Their tip deflection relies on the unmatched coefficients of thermal expansion between layers. The thermal bimorph phenomenon is dependent on the temperature rise within the cantilever and, while previous studies have investigated variations in the thermal profile along the cantilever length, these have usually neglected variations in the thermal profile along the cantilever thickness. The current study investigates the thermal distribution across the thickness of the cantilever. The exact closed form solution to the one-dimensional problem of heat conduction in the composite (layered) domain subjected to transient volumetric heating is developed using the appropriate Green’s function. This solution is applied to a one-dimensional case study of a 3-layer cantilever with an Aluminium heater, a silicon dioxide resistive layer, and a silicon base layer. The aluminium heater experiences volumetric heating at a rate of 0.2 mW/μm3 of 5 μs duration at 100 μs intervals (10 kHz with a 1/20 duty cycle). Benchmark solutions of the temperature at select times and positions are provided. It is shown that there are negligible temperature gradients across the cantilever thickness during the heating and the first ~ 5 μs afterward. These short-lived temperature differences are positively biased with the unmatched thermal expansion coefficients between the layers, though their relative influence on bending is not clear. A simple parametric analysis indicates that the relative magnitude of the temperature differences across the cantilever (compared to the overall temperature) decreases substantially with increasing duty cycle.

Experimental investigation of the intermittent spray heat transfer characteristics of nanofluids in single- and two-phase states

Traditional air-cooled cooling systems used in engineering vehicles consume significant energy and do not align well with future development trends. To address this problem, a single- and two-phase intermittent spray cooling technique for nanofluids was proposed in this study. The effects of the duty cycle and spray frequency on the heat transfer performance and surface temperature uniformity of intermittent spray were determined by experiments, and the thermal behaviour of intermittent spray with different mass fractions of Al2O3 nanofluids was compared in detail. The results revealed that when the spray frequency is constant, the heat transfer coefficient increases with an increase in duty cycle, but the cooling efficiency decreases. The spray frequency mainly affects the average heat transfer surface temperature and its uniformity. At 2.0 Hz, nanofluids with a mass fraction of 0.7 % exhibited the best intermittent spray performance, with an average heat transfer coefficient of 431.8 W/(m2·K). However, a continuous increase in the mass fraction of the nanofluids inhibited the heat transfer performance. The impact of droplets on the heat transfer surface, the liquid film heat transfer process, and the heat transfer characteristics of the nanofluid intermittent spray in the single- and two-phase states were further studied. The results revealed that the heat transfer of intermittent spray mainly depends on the properties and flow rate of the coolant in a single-phase state. Although the heat transfer performance of intermittent spray is evidently enhanced in the two-phase state, it still does not exceed that of continuous spray. These findings highlight the flexibility of nanofluid intermittent spray cooling in enhancing heat transfer control and can inform the development of energy-saving and intelligent cooling systems for engineering vehicles.

Clinical experience with adaptive MRI-guided pancreatic SBRT and the use of abdominal compression to reduce treatment volume.

This work presents a method to treat stereotactic body radiation therapy (SBRT) for pancreatic cancer on a magnetic resonance-guided linear accelerator (MR-linac) using daily adaptation, real-time motion monitoring, and abdominal compression. The motion management and treatment planning process involves a magnetic resonance imaging (MRI) simulation with cine and 3D images, a computed tomography (CT) simulation with a breath-hold CT and a 4DCT, pre-treatment verification and planning MRI, and intrafraction MRI cine images. The results from 26 patients were included in this work. Our motion management process results in consistent motion analysis on the CT simulation, MRI simulation, and each treatment fraction. The liver dome was found to be an overestimate of tumor superior/inferior (SI) motion for most patients. Adding compression reduced SI liver dome motion by 6.2 mm on average. Clinical outcomes are similar to those observed in the literature. In this work, we demonstrate how pancreatic SBRT can be successfully treated on an MR-linac using abdominal compression. This allows for an increased duty cycle compared to gating and/or breath-hold techniques.

Study on the microspot splitting characteristics of pulsed cathodic vacuum arc

The intense pulsed current superimposed on direct current arc discharges can promote arc spot splitting and reduce macroparticle ejection. In this study, the effects of different arc parameters including peak current, magnetic fields, pulse frequency and duty cycle on spot splitting characteristics for the pulsed cathodic arc discharge, as well as mechanisms involved in microspot formation, are investigated. The results show that under the effect of periodic micro-explosive emissions, the micro-spot splitting at the peak of the pulse displays a multi-stage annular expansion phenomenon, and its expansion radius increases with the increaseing peak current; the increasing transverse component of the arc source magnetic field gradually changes the microspot splitting pattern from annular expansion to arc-shaped expansion; the plasma motion after the micro-explosion requires a period of time to “accumulate force.” In addition, an increase in pulse frequency leads to a gradual reduction in the range of the microspot splitting, in which the microspots are in a relative aggregation state; an increase in duty cycle, leads to an instability in the continuous motion of the microspots after the splitting in the peak period. This causes some of the microspots to merge, exhibiting a trend similar to the direct current arc.

Composition-Tunable Properties of Cu(Ag) Alloy for Hybrid Bonding Applications

In the present study, the properties of Cu(Ag) alloy films were studied to evaluate their potential use as an alternate material for interconnection in hybrid bonding. Thin alloy films of Cu(Ag) were deposited by pulsed electrochemical deposition (PED) using a sulfuric acid-based bath, rotating disk electrode, and hot entry. Secondary ion mass spectrometry (SIMS) was used to measure the silver content of the films, with us finding that it decreases with increasing duty cycle. Thereafter, bright field scanning transmission electron microscope (STEM) imaging in combination with energy-dispersive x-ray spectroscopy (EDS) was used to visualize the thin film microstructure and to confirm the uniform distribution of silver throughout the film, with no bands being seen despite the pulsed nature of the deposition. Film resistance was measured by a four-point probe to quantify the impact of Ag content on resistivity, with us finding the expected linear relationship with the Ag content in the film. Furthermore, the coefficient of thermal expansion (CTE) of the films was measured using X-ray diffraction, and modulus and hardness were measured via nanoindentation, revealing linear dependences on the Ag content as well. Notably, the addition of 1.25 atom% Ag resulted in a significant increase in the CTE from 17.9 to 19.3 ppm/K, Young’s modulus from 111 to 161 GPa, and film hardness from 1.70 to 3.99 GPa. These simple relationships offer a range of properties tunable via the duty cycle of the pulsed plating, making Cu(Ag) a promising candidate for engineering wafer-to-wafer metal interconnections.

Ultra‐high voltage gain DC–DC converter based on new interleaved switched capacitor inductor for renewable energy systems

SummaryIn this paper, introduces a DC–DC converter design based on a modified hybrid switched inductor‐switched capacitor architecture, aimed at achieving ultra‐high voltage gain in renewable energy systems (RES). The proposed converter involves adding a modified boosting conversion mode (MBM) that interleaves with the main switch to double the voltage transfer gain. Additionally, a modified switched capacitor (MSC) technique, utilizing two diodes as interleaved components, is integrated into the main and auxiliary switches to verify low voltage stress across them. In addition, modified hybrid switched inductors with capacitors (MSIC) and diodes are employed to validate ultra‐high voltage gain. The main advantages of the proposed converter are its high efficiency, low voltage stress across diodes and MOSFETs, and the utilization of low values of inductors and capacitors at high switching frequencies. In addition, the voltage stress across the inductors of the (MSIC) is reduced as the duty cycle increases. Furthermore, the current stress on the main switch is reduced when the charge of capacitor C1 becomes zero. Mathematical models for both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) of the proposed converter are explored. Furthermore, a dual PI controller is designed for the proposed converter to maintain a high fixed output voltage. In addition, the PCB design and experimental testing of the proposed converter to verify the simulation and laboratory results. Specifically, the proposed converter is designed to boost up voltage (30–40 V) to a variable output voltage between 200 and 300 V at 300 W at efficiency 96.7%.

Effect of voltage and duty cycle on microstructure and corrosion resistance of ZrO2 coating by cathode plasma electrolytic deposition

Power parameters are of importance to determine the microstructure and property of coatings deposited by cathode plasma electrolytic deposition (CPED). In the present study, the effect of power parameters including voltage and duty cycle on the microstructure and anti-corrosion property of zirconia (ZrO2) CPED-coatings was investigated. The results suggested that the as-deposited coatings consisted of t-ZrO2 and m-ZrO2, while the content of t-ZrO2 exceeded 50 %. The content of t-ZrO2 increased with the increase of voltage and decreased with the increase of duty cycle, reaching a maximum of 89.9 %. In addition, as the voltage and duty cycle increased, the porosity of the coating increased from 3.7 % to 15.5 %. Due to the high t-ZrO2 content, high thickness and relatively dense structure, the coatings deposited at 250 V had a superior corrosion resistance in 3.5 wt% NaCl solution. This work will provide a guideline for tailoring high performance ZrO2 CPED-coatings.

Sulfite activation by water film dielectric barrier discharge plasma for ibuprofen degradation: efficiency, comparison of persulfate, mechanism, active substances dominant to pathway, and toxicity evaluation

Herein, we proposed sulfite [S(IV)] activation by water film dielectric barrier discharge plasma (WFDBD) to produce ·SO4- to improve the removal efficiency of ibuprofen (IBP). The results show that the WFDBD/S(IV) system can significantly improve the removal rate of IBP by 22.3% compared with the WFDBD plasma system alone. Compared with persulfate (PS), a small amount of S(IV) can present a high degradation promotion, and S(IV) instead of PS can indeed reduce cost consumption. The active substances including ·OH, ·SO4-, 1O2, and ·O2–, were detected by electron paramagnetic resonance (ESR), and the quenching agents were added to verify the important role and contribution of the above active substances in the degradation of IBP. The degradation of IBP consumes H2O2, O3, ·OH, and ·SO4- in WFDBD/S(IV) system. Through liquid chromatography-mass spectrometry (LC-MS) and density functional theory (DFT) simulation, the degradation pathway of IBP and the role of active substances in the degradation process were inferred. Subsequently, by ECOSAR calculation and seed detection toxicity, it was found that the toxicity was significantly reduced after treatment with WFDBD/S(IV) system. The increase in input power, duty cycle, and solution flow rate all has a positive impact on the degradation of IBP, and IBP degrades better under acidic conditions. Finally, by treating different organic compounds and actual wastewater, it was found that inorganic ions have an impact on the WFDBD/S(IV) system, but the selectivity of the system is low and it has good effects on the treatment of domestic wastewater.

Facebook Prophet Library prediction-based Energy Harvested MAC Protocol (FPEH-MAC)

Data transfer within severe time constraints is crucial for wireless sensor networks used in mission-critical applications, such as industrial control and disaster monitoring. In such applications, exceeding time constraints and facing limitations in longevity can pose threats to human life. The primary option for powering wireless sensor networks is to utilize ambient energy sources like solar energy, thermal energy, etc., which are abundant in nature The lifetime and latency of these networks depend on a well-implemented duty cycle-based MAC protocol, and maximizing the duty cycle is achieved through efficient utilization of harvested and residual energy. Since harvested energy is inherently unpredictable, appropriate forecasting techniques are required. In this study, a prediction-based Energy Harvested MAC protocol (FPEH-MAC) based on the Facebook Prophet library is proposed to maximize the predicted duty cycle of the MAC protocol by forecasting harvested and residual energy. Additionally, this MAC protocol demonstrates an increase in residual energy and duty cycle, ensuring an extended lifecycle for the wireless sensor network. The suggested protocol was evaluated for latency, throughput, percentage increase in residual energy, and packet delivery ratio using OMNET, INET, Python, and MATLAB. The results of the analysis indicate that the proposed technique increases residual energy by 1.2%, enhances throughput by 33.33%, and reduces latency by 9.6% when compared to previous work.

1749-P: Influence of the Biomechanical Environment on Islet Function and Maturity

It is well-established that cells respond to mechanical cues via cytoskeletal remodeling. However, it is not known whether the mechanical environment influences β-cell maturity and function. To examine how mechanical cues influence the β-cell, we used biocompatible substrates with tunable mechanical properties synthesized with elastic moduli ranging from ~3kPa-33 kPa. The surface was coated with extracellular matrix and MIN6 β-like cells were seeded. To independently examine a link between β-cell function and maturity, we examined islets from mice in which β-cells express CaMPARI, a photoconvertible fluorescent protein that in the presence of high Ca2+ activity changes from green to red. For all conditions in MIN6 cells and CAMPARI-expressing islets, we imaged Ca2+ dynamics via Fluo4 at low (2mM) and high glucose (11, 20mM). qPCR was conducted on MIN6 cells (6, 22 kPa) and flow-sorted CaMPARI-expressing β-cells (green, red) to examine expression of genes linked to β-cell function and maturity. With increased substrate stiffness, MIN6 cell Ca2+ oscillations were more robust, including a significant increase in duty cycle (p<0.01) and were more coordinated, consistent with increased excitability. With increasing stiffness, there was significantly decreased expression of Sur1, Kir6.2, Ins2, Pdx1, Fltp, and Ecad (p<0.01). Thus, the dynamics and coordination of Ca2+ activity is mechanoresponsive and may result from altered β-cell maturity. In CaMPARI islets, Ca2+ oscillations were more robust and coordinated for photo-converted red cells which marks cells with higher Ca2+, compared to green cells. In these red cells that show higher Ca2+, qPCR showed significantly increased expression of cFos, but decreased expression of Pdx1 and Ins2, again showing more excitable cells showed altered maturity. In conclusion, our results suggest there may be an inverse relationship between β-cell maturity and function. Further, that the maturity and function of β-cells is responsive to the mechanical environment. Disclosure K.Vazquez: None. R.K.Benninger: None. Funding National Institutes of Health (R01DK102950, R01DK106412)

Investigating the effect of tool material on performance parameters in electric discharge machining through FEM

The study aims to fill the gap in the existing literature by investigating the effects of various tool materials, including copper, tungsten carbide, and brass, on performance parameters in electric discharge machining (EDM) simulations. The authors developed a modified gaussian heat flux equation that incorporates the electrical resistivity of both the tool and workpiece, based on prior experimental investigations. The authors further developed a finite element model that incorporates the modified Gaussian heat flux equation, spark radius, and fraction of heat transferred to workpiece as a function of pulse on time and pulse current, latent heat, specific heat values, and thermal conductivity properties. The outcomes of the simulation indicated that the Cu tool exhibited the minimum MRR and SR values when subjected to a current of 9 amps and a duty cycle of 0.4, as well as a current of 12 amps and a duty cycle of 0.6. The results also indicate that the brass tool displayed marginally elevated MRR and SR, whereas the Tungsten carbide tool exhibited the highest MRR and SR. The simulation results for all three tool materials showed similar trends, consistent with prior research. Also, an increase in gap voltage, pulse current and duty cycle was observed to correspond with increased MRR and SR. Authors also observed that as electrode material electrical conductivity increased, so did workpiece material residual stresses. These results assist with the choice of tool materials for EDM processes, allowing for finer control over performance parameters and greater machining efficiency.

A fluid model of pulsed direct current planar magnetron discharge

We simulated a pulsed direct current (DC) planar magnetron discharge using fluid model, solving for species continuity, momentum, and energy transfer equations, coupled with Poisson equation and Lorentz force for electromagnetism. Based on a validated DC magnetron model, an asymmetric bipolar potential waveform is applied at the cathode at 50–200 kHz frequency and 50–80% duty cycle. Our results show that pulsing leads to increased electron density and electron temperature, but decreased deposition rate over non-pulsed DC magnetron, trends consistent with those reported by experimental studies. Increasing pulse frequency increases electron temperature but reduces the electron density and deposition rate, whereas increasing duty cycle decreases both electron temperature and density but increases deposition rate. We found that the time-averaged electron density scales inversely with the frequency, and time-averaged discharge voltage magnitude scales with the duty cycle. Our results are readily applicable to modulated pulse power magnetron sputtering and can be extended to alternating current (AC) reactive sputtering processes.

Modulation of the plasma radial uniformity in pulsed dual-antenna inductively coupled plasmas

Pulse modulation in inductively coupled plasmas (ICPs) has been proven as an effective method not only to restrain the charging effect in etching trenches but also as a potential approach to ameliorate the plasma uniformity. In this paper, a two-dimensional fluid model is employed to systematically study the modulation of the radial uniformity in pulsed dual-antenna Ar ICPs. The inner four-turn coils are connected to a continuous wave at the current of 5.0 A, and the outer three-turn coils are pulse modulated at various duty cycles and currents. The results indicate that when the outer coil current is fixed at 7.0 A, the electron density always shows an off-center distribution during the active-glow period when the duty cycle increases from 20% to 60%, due to the stronger electric field induced by the higher outer coil current. Although the ionization mainly happens at the reactor center during the after-glow period, the electron density distribution evolves from a center-high profile to a rather uniform distribution as duty cycle increases. Under the combined influence, the time-averaged electron density over one pulse period shifts from center-high over uniform to edge-high. When the pulse duty cycle is fixed at 50%, the time-averaged electron density distribution shifts from a center-high profile over uniform to an edge-high profile, as the outer coil current increases from 5.7 to 7.7 A. The results obtained in this work could help to optimize the plasma radial uniformity, which plays a significant role in improving the large-area plasma processing.

Influence of the Duty Cycle of Pulse Electrodeposition-Coated Ni-Al2O3 Nanocomposites on Surface Roughness Properties

In this study, the viability of duty cycle variation was explored as a potential method to improve the mechanical and surface roughness properties of Ni-Al2O3 nanocoatings through pulse electrodeposition. The areal and surface roughness properties of nanocomposite pulse electrodeposition-coated materials with varying duty cycles from 20% to 100% was studied with the analysis of bearing area curves and power spectral densities. Results demonstrate that with decrease in duty cycle, there was an enhancement in aerial roughness properties from 0.348 to 0.195 µm and surface roughness properties from 0.779 to 0.245 µm. The change in surface roughness was due to grain size variation, resulting from the varying time intervals during pulse coatings. This increase in grain size with the change in duty cycle was confirmed with the scanning electron microscope. In addition, an increase in grain size from 0.32 to 0.92 µm with an increase in duty cycle resulted in a decrease in nanohardness from 4.21 to 3.07 GPa. This work will provide a novel method for obtaining Ni-Al2O3 nanocomposite coatings with improved surface roughness and hardness properties for wider industrial applications.

Two common European songbirds elicit different community responses with their mobbing calls

Heterospecific communication is common for birds when mobbing a predator. However, joining the mob should depend on the number of callers already enrolled, as larger mobs imply lower individual risks for the newcomer. In addition, some ‘community informant’ species seem more reliable regarding the information transferred in mobbing calls. Birds should therefore rely on both the number of callers and the species identity of the caller(s) when mobbing. In the present study, we tested the potential interaction between two acoustic cues. In a playback experiment, we modified the number of callers (through an increased number of calling individuals correlated to an increased duty cycle) and the emitter species (crested tits versus coal tits). Overall, we found that soundtracks with three callers triggered more mobbing than soundtracks with one caller and that soundtracks with coal tits’ calls triggered more mobbing than soundtracks with crested tits’ calls. Our results therefore support the hypothesis that birds consider both the species and the number of callers when joining a mobbing chorus in winter. Finally, we replicated the experiment in spring and did not record the same responses from the bird community. Indeed, only soundtracks with three coal tits triggered a mobbing response, suggesting therefore that the seasonal context can affect the results of studies on heterospecific communication. The potential mechanisms implicated in the varying responses to different acoustic cues and different seasons are discussed and should deserve further investigations.

Effect of Pulse Duty Cycle and Oxidation Time on Microstructure and Properties of Micro-arc Oxidation Coatings on Ti6Al4V Alloy

Micro-arc oxidation (MAO) technology can in-suit generate coatings with high hardness and strong adhesion on the surface of titanium alloy, thereby greatly improve the application range of titanium alloy. The morphology and properties of coatings are controlled by changing electrical parameters such as duty cycle and oxidation time. This work mainly aims to study the influence of different duty cycles and oxidation times on MAO coatings microstructures and properties of Ti6Al4V alloy under the condition of constant voltage and pulse frequency. The scanning electron microscopy (SEM) and X-ray Diffractometer (XRD) were used to investigate into MAO coatings microstructure and phase composition. The roughness, porosity, thickness, and microhardness of MAO coatings were evaluated respectively by roughness tester, thickness gauge, and microhardness tester. The results show that surface morphology of the MAO coatings change from crater-like micropores to foam-like protrusions with the enhancement of duty cycle and oxidation time. When duty cycle is 50% and oxidation time is 30 min respectively, the ejection of the molten material made the MAO coating surface appear foam-like protrusions, and the surface morphology is seriously damaged. When the oxidation time and the duty cycle are 30 min and 10% respectively, the rutile phase intensity is the maximum, and further increasing the duty cycle will lead to a rutile phase decrease. In a limit range, the hardness rise with increase of oxidation time and duty cycle. The highest hardness is 668.85 HV.