Showing papers by "Andrej Atrens published in 2019"
TL;DR: In this article, the traditional gravimetric method can evaluate effectively the corrosion behavior of Mg alloys, and it is shown that the corrosion rate increases with relative humidity (RH) and concentrations of aggressive species such as chloride ions.
109 citations
TL;DR: In this article, the influence of Zn on the strain hardening of as-extruded Mg-xZn magnesium alloys was investigated using uniaxial tensile tests at 10−3 s-1 at room temperature.
99 citations
TL;DR: In this paper, super-hydrophobic films were synthesized on the Mg alloy AZ31 by modifying in-situ grown Mg-Al layered double hydroxide (LDH) films with stearic acid, sodium laurate, myristic acid and PFDTMS.
88 citations
TL;DR: Both SLM-manufactured FCCZ and FBCCZ scaffolds exhibited good biocompatibility, with osteoblast-like cells attaching, growing, and spreading in a healthy way on their surfaces after culturing for different periods up to 28 d.
75 citations
TL;DR: In this paper, an as-rolled Mg-Nd-Zn alloy was subjected to FSP and the microstructure in the processed zone of the FS-400 rpm alloy exhibited refined grains, a more homogenous grain size distribution, less second phases, and stronger basal plane texture.
71 citations
TL;DR: In this paper, the micro-arc oxidation (MAO) produced a coating layer that separated the substrate from the solution so that the MAO treated condition had a corrosion rate that was 1/76 of that of the as-cast condition.
61 citations
TL;DR: In this paper, the authors investigated the strain hardening behavior of Mg-xY alloys and found that the average grain size reduces from 19.8 to 12.2 as the Y content adds from 1'wt% to 2'wt%.
53 citations
TL;DR: In this article, the synergistic effects of biodegradation of ZK30, antibacterial function of Cu and grain refinement by selective laser melting (SLM) were utilized to prepare high-performance antibacterial Zk30-Cu alloys.
53 citations
TL;DR: In this paper, a magnesium-aluminum layered double-hydroxides (Mg Al LDHs) was fabricated on the surface of Mg alloy AZ31, followed by electrophoretic deposition of an Al2O3 nanoparticles layer.
52 citations
TL;DR: In this article, the formation and characteristic corrosion resistance of alternately lamellar arranged α and β in as-cast AZ91 Mg alloy were investigated as an independent micro-constituent identity.
51 citations
TL;DR: In this paper, Mg-Al layered double hydroxides (LDHs) were deposited on the anodized magnesium alloy AZ31 via an easy in-situ method.
Abstract: Mg-Al layered double hydroxides (LDHs) were deposited on the anodized magnesium alloy AZ31 via an easy in-situ method, and the surfaces of MgAl-LDHs were modified with myristic acid (MA) and 1H, 1H, 2H, 2H-Perfluorodecyltrimethoxysilane (PFDTMS). The obtained results showed that LDHs with the biggest flakes were preferential sites for absorption of MA, while unfavorable for the adsorption of PFDTMS. All of films modified with MA were superhydrophobic. The corrosion behavior of the AZ31 with modified LDH films was evaluated using hydrogen collection, electrochemical impedance spectroscopy (EIS), polarization potentiodynamic curves and the immersion tests. The superhydrophobic films considerably improved the corrosion performance of the LDH films on the AZ31 substrate.
TL;DR: In this article, the elastic modulus of the extruded Mg-Gd-Y-Zn-Mn alloy with a trace amount of Si was shown to be 49.3 GPa, 8 GPa greater than that of extruded pure Mg, which was attributed to the high density of thermal mismatch dislocations in the vicinity of the interfaces between the reinforcing phase and the α-Mg matrix.
TL;DR: In this article, Mg-6Al-1Zn-xFe alloys have an attractive combination of corrosion and mechanical properties, which holds a bright future for fracturing balls applications.
TL;DR: In this paper, the epoxy resin was doped with Ce-loaded zeolite microparticles (CeNaX), and was coated on PEO treated AZ31 substrate.
TL;DR: In this article, the authors studied how Be influences Mg alloy oxidation and found that Be microalloying significantly decreased the oxidation rate at 500 °C and increased the ignition temperatures of as-cast Mg-2Zn, Mg2Sn, AS21, and ZC63.
TL;DR: A range of recommendations on the in vitro biocorrosion assessment of Mg alloys are outlined and updated, based on experience in the field and the lessons learned through years of experiments.
Abstract: Magnesium (Mg) alloys are achieving good clinical success in applications as temporary biodegradable medical implants. However, the study of the corrosion in medical environments (biocorrosion) is still ongoing. Much of this study is conducted via laboratory (i.e., in vitro) immersion tests, which can be challenging. We have outlined and updated a range of recommendations on the in vitro biocorrosion assessment of Mg alloys, based on our experience in the field and the lessons learned through years of experiments. We hope these recommendations will help to improve future biocorrosion testing and provide insight for both researchers with experience in this field and those seeking to enter it.
TL;DR: The average corrosion rate for WE43B was somewhat lower than the intrinsic corrosion rate of Mg as shown by high purity Mg, attributed to (a) no corrosion acceleration by the small second phase particles, and (b) a more protective surface film as mentioned in this paper.
Abstract: The corrosion rates of the Mg alloys immersed in 3.5 wt% NaCl solution saturated with Mg(OH)2 were in the following increasing order: WE43B (0.23 mm/y) < EV31A (0.88 mm/y) < pure‐Mg (1.6 mm/y) < ZE41A (8.5 mm/y). The average corrosion rate for WE43B was somewhat lower than the intrinsic corrosion rate of Mg as shown by high‐purity Mg, attributed to (a) no corrosion acceleration by the small second phase particles, and (b) a more protective surface film. The high corrosion rates of ZE41A were attributed to the presence of a coarse semicontinuous T‐phase, which served as strong cathodic sites.
TL;DR: In this paper, the following for magnesium alloys: fundamentals of oxidation and burning, influence of alloying on oxidation, and theoretical models for improved oxidation resistanability and combustion.
Abstract: This paper reviews the following for magnesium (Mg) alloys: (a) fundamentals of oxidation and burning; (b) influence of alloying on oxidation; (c) theoretical models for improved oxidation resistan...
TL;DR: In this paper, the as-extruded Mg-Sr alloy was coated using micro-arc oxidation and also using a phosphate conversion coating to improve the corrosion resistance.
Abstract: As-extruded Mg–Sr alloy, a kind of promising biodegradable biomedical material, was coated using micro-arc oxidation and also using a phosphate conversion coating. The corrosion behaviors were investigated using Hanks’ solution. The corrosion of the as-extruded Mg–Sr alloy became more serious with increasing immersion time; that is, the corrosion pits became more numerous, larger and deeper. The micro-arc oxidation coating and the phosphate conversion coating were effective in improving the corrosion resistance of the as-extruded Mg–Sr alloy. The micro-arc oxidation coating was much more effective. Moreover, the as-extruded Mg–Sr alloy and the coated as-extruded Mg–Sr alloy exhibited lower corrosion rates than the as-cast Mg–Sr alloy and the corresponding coated as-cast Mg–Sr alloy, indicating that the corrosion properties of the coated samples are dependent on their substrates. The finer microstructure of the substrate of the as-extruded condition corroded much slower. The corrosion resistance of the coated Mg–Sr alloy depended on the coating itself and on the microstructure of the substrate.
TL;DR: In this paper, a selective laser melting (SLM) was used to produce a Fe/graphene oxide (GO) composite from pure Fe and GO powders, which is expected to increase the biodegradation rate of Fe.
Abstract: Pure iron (Fe) is a promising biodegradable metal. However, a too slow biodegradation rate in physiological environments restricts its clinical application. This work produced a Fe/graphene oxide (GO) composite from pure Fe and GO powders, through selective laser melting (SLM). GO is expected to increase the biodegradation rate of Fe. The microstructure, hardness, and corrosion behavior are investigated. The results demonstrated that the GO is distributed relatively uniformly at grain boundaries and inside the matrix. The SLMed Fe/GO composite had finer grain size, higher hardness, and faster biodegradation rate compared to the SLMed pure Fe.
TL;DR: The microstructure and corrosion properties of AZ31 alloy with micro-alloying Ca and Ce addition were studied by SEM, EBSD and EDS as mentioned in this paper, and the corrosion behavior was evaluated by immersion tests and electrochemical tests.
Abstract: The microstructure and corrosion properties of AZ31 alloy with microalloying Ca and Ce addition were studied. The microstructure was examined by SEM, EBSD and EDS. The corrosion behavior was evaluated by immersion tests and electrochemical tests. The microalloyed alloys had much finer grains than the AZ31 alloy. The AZ31 alloy possessed a small quantity of coarse Al8Mn5 phase particles. In contrast, the microalloyed alloys possessed a relatively higher number of the smaller second phase particles: Al2Ca, Al(11)Ce3 and Al8CeMn4 besides Al8Mn5. The corrosion rates ranked as AZ31-0.2Ca < AZ31-0.2Ca-0.2Ce < AZ31-0.2Ce < AZ31. The Ca micro-alloying was more effective in decreasing the corrosion rate than Ce, attributed to the Ce-containing second phase causing more severe galvanic corrosion with the alpha-Mg matrix than the second phase containing Ca, and that Ca was in the corrosion products, which could improve the protectiveness of the corrosion products film.
TL;DR: In this paper, the effect of alloying with Al−Si eutectic on the microstructure and mechanical properties of the three alloys was investigated to investigate their effect on the formation of different types of Al−Li precipitates.
TL;DR: The Mg tack had a pull-out force comparable to those of the commercially available tacks, and had a more ductile failure mode (i.e. the tacks deformed prior to failure), compared to the commercial tacks which pulled directly from the tissue with no deformation.
Abstract: A prototype magnesium (Mg) surgical tack is tested comparatively against commercially available tacks made of titanium (ProTacktm, Medtronic) and PLGA (AbsorbaTacktm, Medtronic). The pull-out force is measured in situ in a lap-shear pull-out test, using porcine abdominal muscle tissue as a model. The Mg tack had a pull-out force comparable to those of the commercially available tacks. The majority of the Mg tacks also had a more ductile failure mode (i.e. the tacks deformed prior to failure), compared to the commercial tacks which pulled directly from the tissue with no deformation. The Mg tacks deformed as they were removed from the tissue, causing less damage to the tissue in the process. This is the first reported use of a Mg alloy in this application, and the proof of concept indicates that this is an area that deserves further interest and study.
07 May 2019-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the ultrasonic fatigue behavior was studied for a 1.9-GPa grade ultra-high-strength MSS with a composition of 13Co-13Cr-3.5Mo-4.5Ni-0.5Ti (at. %).
Abstract: Super-high-strength maraging stainless steel (MSS) is of great interest for the next generation aircraft. The ultrasonic fatigue behavior was studied for a 1.9 GPa grade ultra-high-strength MSS with a composition of 13Co-13Cr-3.5Mo-4.5Ni-0.5Ti (at. %). The ultra-high cycle fatigue limit was 560 MPa. Cracking initiated on the surface or at non-inclusion interior sites. A crack initiation and propagation model was proposed through a discussion of the fracture mechanism: (i) the surface defect-induced failure was caused by machining marks with a critical size of 0.6 μm; and (ii) the interior matrix induced failure was caused by a defect larger than 3.3 μm. The fatigue number (Nf) of the surface induced failures ranged from 6 × 104 to 1.4 × 105, while that of the interior induced failures was much longer, ranging from 8.6 × 106 to 3.2 × 108.
TL;DR: In this paper, the evolution of the microstructure and texture was investigated using optical microscopy, transmission electron microscopy and electron backscattered diffractometry during four cycles of cumulative roll bonding applied to an Al-0.4 Er alloy.
TL;DR: The effect of B addition on the microstructure and mechanical properties of AM50 was investigated, and the mechanism of grain refinement was clarified, resulting in improved mechanical properties and YTS, UTS, and elongation of as cast AM50 + 0.15 wt.% B alloy.
Abstract: The effect of B addition on the microstructure and mechanical properties of AM50 was investigated, and the mechanism of grain refinement was clarified. Optical microscopy, X-ray diffraction, scanning electron microscopy, and electron probe microanalysis were used to characterize the microstructure evolution. The grain size of as-cast AM50 decreased from 550 μm to 100 μm with the B content increasing from 0 to 0.15 wt.%. AlB₂ particles in the Al-3B master alloy transformed to Mg-B, and acted as the grain refiner. The addition of B to as cast AM50 alloy results in improved mechanical properties of AM50 + xB alloys. For instance, the YTS (yield tensile strength), UTS (ultimate tensile strength), and elongation of as cast AM50 + 0.15 wt.% B alloy was 94 MPa, 215 MPa, and 12.3%.
TL;DR: In this paper, the root cause of crack formation was the low fracture toughness caused by a combination of a high hydrogen content and phosphorous segregation, caused by an inappropriate heat treatment.
TL;DR: The graphene coating decreased the corrosion rate of AZ31 by three orders of magnitude and the corrosion behavior was evaluated from potentio-dynamic polarization curves and electrochemical impedance spectroscopy (EIS).
Abstract: A graphene coating, prepared via spin coating on the Mg alloy AZ31, was characterized using Raman spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The Raman spectra indicated that the graphene spin coatings were uniform over the surface of AZ31. The SEM indicated the chemical composition of the graphene coating. The XPS analysis indicated that the carbon was mainly composed of conjugated double bonds. The corrosion behavior was evaluated from potentio-dynamic polarization curves and electrochemical impedance spectroscopy (EIS). The graphene coating decreased the corrosion rate of AZ31 by three orders of magnitude.
TL;DR: In this article, the authors investigated the mechanical properties of a CrNi-Mo-alloyed rock drill steel tempered at different temperatures from 150 to 550 degrees C and found that the highest strength, hardness, and impact energy occur when the steel is tempered at 180 degrees C. The mechanism of changes of impact energy and hardness with tempering temperature is proposed.
Abstract: This research investigates the mechanical properties of a Cr-Ni-Mo-alloyed rock drill steel tempered at different temperatures from 150 to 550 degrees C. The highest strength, hardness, and impact energy occur when the steel is tempered at 180 degrees C. Strength, hardness, and impact energy decrease with increasing tempering temperature from 180 to 400 degrees C. For tempering temperatures higher than 400 degrees C, the steel exhibits: 1) an increase in impact energy; 2) an increase in strength and hardness when tempered at 420, 450, and 480 degrees C; and 3) a gradual decrease in strength and hardness when tempered at temperature higher than 480 degrees C. The mechanism of the changes of impact energy and hardness with tempering temperature is proposed.