AM Series Research Articles

Investigation of in-vitro biocompatibility and in-vivo biodegradability of AM series Mg alloys

ABSTRACT In this study, in vitro/vivo biocompatibility experiments of Mg-Al-Mn alloy were carried out, and AM50 and AM60 alloys were used in the experiments. Immersion and potentiodynamic corrosion have been applied to these alloys in vitro. For biocompatibility, cytotoxicity test was performed. A total of 40 rats were used for the in-vivo experiment. AM series alloys were surgically placed in the femoral condyle as mini screws and monitored radiographically. AM alloys were removed together with the femur at the end of 7 weeks and further examined. After in-vivo application, the biodegradability level was successfully concluded with blood mineral analysis and urinalysis. In this study, the bioprocess of AM series Mg alloys with Al and Mn additions has been completed. As a result, the AM alloys used can be classified as biocompatible and biodegradable materials.

Thermal Properties of AM Series Magnesium Alloys

This paper presents experimental investigation on thermal properties (thermal diffusivity and thermal conductivity) of AM series cast magnesium alloys. The effects of the changing in Al content (from 2 to 9 Al and constantly 0.5 Mn, wt. %) in the alloys on thermal properties, density and hardness were comparatively analyzed. It was observed that intermetallic phases (Mg17Al12 ve Al8Mn5) found in the microstructure of the alloys have an effect on thermal diffusivity, thermal conductivity, density and also hardness. The thermal properties of the alloys were decrease with increasing Al content in the alloy. The thermal properties of the alloys were increase with increasing temperature (the temperature range from 25°C to 400°C). The highest thermal diffusivity was measured on AM20 alloy and the lowest thermal diffusivity were observed on AM90 alloy.

Spatiotemporal Variation of Hydrogen and Oxygen Stable Isotopes in the Yarlung Tsangpo River Basin, Southern Tibetan Plateau

Characterization of spatiotemporal variation of the stable isotopes δ18O and δD in surface water is essential to trace the water cycle, indicate moisture sources, and reconstruct paleoaltimetry. In this study, river water, rainwater, and groundwater samples were collected in the Yarlung Tsangpo River (YTR) Basin before (BM) and after the monsoon precipitation (AM) to investigate the δ18O and δD spatiotemporal variation of natural water. Most of the river waters are distributed along GMWL and the line of d-excess = 10‰, indicating that they are mainly originated from precipitation. Temporally, the δ18O and δD of river water are higher in BM series (SWL: δD = 10.26δ18O+43.01, R2 = 0.98) than AM series (SWL: δD = 9.10δ18O + 26.73, R2 = 0.82). Spatially, the isotopic compositions of tributaries increase gradually from west to east (BM: δ18O = 0.65Lon (°)-73.89, R2 = 0.79; AM: δ18O = 0.45Lon (°)-57.81, R2 = 0.70) and from high altitude to low (BM: δ18O = −0.0025Alt(m)-73.89, R2 = 0.66; AM: δ18O = −0.0018Alt(m)-10.57, R2 = 0.58), which conforms to the “continent effect” and “altitude effect” of precipitation. In the lower reaches of the mainstream, rainwater is the main source, so the variations of δ18O and δD are normally elevated with the flow direction. Anomalously, in the middle reaches, the δ18Omainstream and δDmainstream values firstly increase and then decrease. From the Saga to Lhaze section, the higher positive values of δ18Omainstream are mainly caused by groundwater afflux, which has high δ18O and low d-excess values. The δ18Omainstream decrease from the Lhaze to Qushui section is attributed to the combined action of the import of depleted 18O and D groundwater and tributaries. Therefore, because of the recharge of groundwater with markedly different δ18O and δD values, the mainstream no longer simply inherits the isotopic composition from precipitation. These results suggest that in the YTR Basin, if the δ18O value of surface water is used to trace moisture sources or reconstruct the paleoaltimetry, it is necessary to rule out the influence from groundwater.

Mg17Al12 intermetallic modified with Yttrium additions

Mg17Al12 is the principal intermetallic second phase in the Mg–Al based alloys (AM series) that significantly affects their mechanical performance. Modification of this intermetallic has been possible with rare earth elements, resulting in mechanical performance improvement of the AM alloys. The modification of the intermetallic has been studied with respect to alteration of the morphology, but little is known about the effect of alloying elements on the intrinsic properties of Mg17Al12 which has a complex crystal structure. In previous studies on first principle simulations of the phase, the effect of alloying additions was not well-investigated. The current experimental study investigates the effect of low and high Yttrium (Y) additions on the mechanical properties, microstructure, and crystal structure of Mg17Al12. Scanning electron microscopy, electron probe microanalysis, X-rays diffraction, ultrasonic and mechanical testing along with thermodynamic calculations are employed to better understand the role of Y in the modification of Mg17Al12. Low Y additions decrease the lattice constant of β phase, but higher amounts present an opposite trend. According to the elastic moduli calculations Mg17Al12 is a ductile phase although Y slightly makes it more brittle. The Young's, shear, and bulk moduli increase with Y additions.

Glacier Retreat in Iceland Mapped from Space: Time Series Analysis of Geodata from 1941 to 2018

In recent decades, glaciers outside Greenland and Antarctica have shown increasingly rapid rates of mass loss and retreat of the ice front, which is associated with climatic and oceanic warming. Due to their maritime location, Icelandic glaciers are sensitive to short-term climate fluctuations and have shown rapid rates of retreat and mass loss over the last decade. In this study, historical maps (1941–1949) of the US Army Map Service (AMS series C762) and optical satellite imagery (Landsat 1, Landsat 5, Landsat 7, Landsat 8, and Sentinel-2) are used to study the Langjökull, Hofsjökull and Vatnajökull ice caps. By the help of the Normalized Difference Snow Index (NDSI), the glacier terminus fluctuations of the ice caps from 1973 to 2018 and the Equilibrium Line Altitude (ELA) from 1973 to 2018 are analyzed. The results are compared with climate data, especially with mean summer temperatures and winter precipitation. Due to the negative temperature gradient with increasing altitude, bivariate histograms are generated, showing the glaciated area per altitude zone and time, and providing a prediction of the future development until 2050 and beyond. The results indicate that Langjökull, Hofsjökull and Vatnajökull are retreating and advancing over the study period in correlation with the mean summer temperature, with a steady decrease over time being the clearest and most significant trend. The lower parts of the glaciers, thus, will probably disappear during the next decades. This behaviour is also evident by an exceptional increase of the ELA observed on all three glaciers, which leads to a reduction of the accumulation zone.

Magnesium Corrosion Research Special Issue

Welcome to the second special issue of CORROSION devoted to current trends in magnesium corrosion research. This issue follows our original guest co-edited special issue published in May 2017, as well as two prior issues dedicated to magnesium and aluminum-magnesium alloys. The high susceptibility of magnesium and its alloys to corrosion is acknowledged to be the principal barrier to its widespread use as a structural metal. Hence, the subject of corrosion and protection of magnesium and its alloys remains one of the most highly cited fields in corrosion science and continues to stimulate significant interest and debate.It is with great pleasure that we serve as guest co-editors for this issue, which presents invited original articles contributed by research groups from the United States, Canada, Germany, Australia, Malaysia, Sweden, and the United Kingdom. We are extremely grateful to the authors for finding the time to compile their manuscripts and to the reviewers for the rigor of their efforts, given the current unprecedented challenges of the COVID-19 pandemic. In addition, we would like to extend our gratitude to the editorial team of Prof. John Scully, Sammy Miles, and Marlene Walters for their invaluable advice and guidance.For this latest special issue, we have sought to compile a selection of articles that cover a broad range of interests, which reflect the current cutting-edge of magnesium corrosion research. The first papers, by Glover and coauthors, seek to further the understanding of the phenomenon of cathodic activation of a corroding magnesium surface and demonstrate how a novel germanium alloying addition mitigates this effect, thus reducing the corrosion rate.These are followed by a description of the development of a novel experimental method that allows dynamic pH control of an unbuffered test electrolyte, by Curioni, et al., along with preliminary findings on the pH-dependent electrochemical response of pure Mg. Several articles focus on the localized corrosion behavior of technologically important Mg alloys such as ZEK100 (Kousis, et al.) and Magnox Al-80 alloy (Clark, et al.), used in the automotive sector and first generation of U.K. nuclear reactions, respectively, and characterized using a scanning vibrating electrode technique. The same methodology, in combination with scanning electrochemical microscopy, is used by others (Thomas and coauthors) to investigate the time-dependent localized corrosion behavior of welded AM series alloy surfaces.Another two papers focus on Mg corrosion inhibition, one using an empirical approach to investigate the effectiveness of lithium carbonate technology on AZ31 alloy (Kish and coauthors) and the other using density functional theory calculations to optimize the inhibitive properties of bipyridyl-based derivatives (Feiler, et al.). The importance of magnesium alloys as biodegradable materials for potential in vivo applications is addressed in contributions by Höhlinger, et al., and Chen and coauthors. The former describes a multifaceted approach to evaluate the corrosion rate of WE43 alloy in the presence of different types of surface coatings, while the latter quantifies the biocompatibility of a Mg surface immersed in simulated body fluid as a function of corrosion product film composition. Finally, there are also valuable contributions which investigate the corrosion of binary Mg alloys prepared by high energy ball milling of nanocrystalline powders, by Gupta and coauthors, and the influence of carbon dioxide on the atmospheric corrosion of Mg-Al alloys in the presence of sodium chloride deposits, by Esmaily and coauthors.We hope that you find the selection of articles both stimulating and informative.

Optimization of cutting forces and surface roughness in dry turning of AM magnesium alloy using Taguchi method

This study aimed to analyze the feed force, cutting force, and surface roughness deviations through CNC lathe turning operation of AM series magnesium alloy. Machining operations were performed using Tungsten Carbide insert with nose radius of 0.8 mm and by varying the basic cutting parameters like feed, cutting speed, and depth of cut. Throughout the experiments, the geometry of the tool was not changed and the cutting fluids are not used in turning operation. The investigation is performed only on the tungsten carbide inserts, and these were changed continuously to prevent the tool wear. The experiments are carried out as per Taguchi’s L27 orthogonal array for cutting force, feed force, and surface roughness under dry cutting conditions. The results prove that the depth of cut and feed mainly influences the Cutting force and feed force. For Surface roughness, the feed and depth of cut are perceived as the influencing controlling factors. Finally, the optimum results are verified by the experimentation.

Effect of tool nose radius in turning of novel Mg alloy

Machining parameters play a significant role in controlling the response variables such as cutting force, temperature, surface roughness, chip shape, etc. Therefore, a judicious selection of machining parameters becomes vital. Many studies have been done to analyze the effect of turning parameters on the response variables in the past. However, the literature on the influence of nose radius has been scanty. In this study, the effect of the nose radius of carbide inserts on the cutting force, cutting temperature, and surface roughness has been analyzed. A novel AM (Mg-7 wt%Al-0.9 wt%Mn) series Mg alloy developed using stir casting has been selected for the turning operation. The results showed that the nose radius has a strong influence on the cutting force and surface roughness. The cutting force is proportional to the nose radius, whereas the surface roughness is inversely proportional to the nose radius. The effect on temperature was lesser compared to the cutting force and surface roughness. Furthermore, the SEM images corroborate the obtained results.

Alloying criteria and investigations on the properties of novel AM series alloy fabricated using stir casting

Abstract Magnesium alloys are being used in different sectors for several applications. The low density and high strength to weight ratio have made them indispensable. However, it is observed that Mg alloys are less preferred for the fabrication of critical and complex parts. The inferior mechanical and corrosive properties, along with high inflammability, limit their usage for several applications. The mechanical and physical properties can be enhanced by varying the weight percentage of alloying elements along with an appropriate process for its development. The paper discusses an approach for selection of the alloying elements and their weight percentage with the help of phase diagrams, vital inputs from past literature and properties of commercially available Mg alloys. The developed AM series alloy (Mg-7 wt%Al-0.9 wt%Mn) has shown improvement in the mechanical properties vis-a-vis the existing AM series alloys. The elastic modulus and hardness were observed 24.3% and 16.21% higher than the maximum values of existing AM alloys. For the development of alloy, a systemized stir casting setup was used, which ensured uniform mixing of alloying elements and essentially played an active role in enhancing the mechanical properties.

‘It's still the same old story’: The current southern Transdanubian approach to the Neolithisation process of central Europe

The pivotal role of the western Carpathian basin in the transmission of key inventions of food production towards central Europe is an accepted fact in Neolithic research. Southern Transdanubia in western Hungary may serve as a unique ‘laboratory’ for targeted investigations, as north Balkan and central European characteristics overlap in the region. Site-based studies of recently excavated late 6th millennium cal BC Neolithic settlements provide insights into possible patterns in the development of longhouse architecture and settlement layout, different combinations of material culture and their alterations, and technology transfer on a regional scale.In order to gain a more complex view of these themes, three micro-regions have been selected around key sites for further study of different vantage points between Lake Balaton and the Dráva/Drava river. The southernmost one is located in the Southern Baranya Hills, the second along the Danube on the northern fringes of the Tolna Sárköz and in the adjacent section of the Sárvíz valley, while the third lies in the central section of the southern shore of Lake Balaton. Field surveys including the systematic collection of surface finds complemented by geomagnetic prospections can contribute significantly to the reconstruction of settlement clusters.Absolute chronology has become an important research focus due to larger sets of radiocarbon dates interpreted within a Bayesian framework. The two dominant scenarios for the start of the westward expansion of the LBK are hard to harmonise with each other. An approach that estimates the beginning of the process around 5500 cal BC at the latest gains support from a west-central European perspective. In contrast, recent radiocarbon dating programmes with formal modelling of AMS series within a Bayesian framework estimate the appearance of the LBK west of the Carpathian basin hardly before 5350–5300 cal BC. The latter view provides the potential of harmonising the Neolithisation of central Europe with the emergence of the Vinča culture, at least in its northernmost region. Beyond this debate, ancient DNA analyses have enriched the discussions on migration, demic diffusion and the scale of hunter-gatherer contribution to the process with fresh arguments.

Casting of High Aluminum Content AM Series Magnesium Alloys by Using a Horizontal Twin Roll Caster

In this paper, twin roll casting of magnesium alloys with high aluminum content such as, Mg-11 mass%Al-0.2 mass%Mn, Mg-12 mass%Al-0.2 mass%Mn, Mg-13 mass%Al-0.2 mass% have been performed for the purpose of use as an original material for hot forging. Also the mechanical properties of the cast materials were examined. A 10 miri-meters thick strip was cast by the use of a horizontal twin roll caster. The microscopic observation was conducted to investigate into the precipitation of the metal compounds such as Mg17Al12, and the Vickers hardness of the cast strips test were performed. From the result of the roll casting experiments, a 10 mm thick strip was continuously cast at a roll speed of 3.1 m/min. The average grain size of the casting strips was about 46 micron meters. When the aluminum content was 13%, the hardness of the twin roll cast (TRC) strips became 1.7 times higher than that of extruded AZ 31. Also, a uniaxial compression test at elevated temperature was conducted to obtain a true strain-true stress curve for examining possibility of direct hot forging (DHF) of TRC magnesium alloys with high aluminum content.

Corrosion and Residual Strength Analysis of High Pressure Die Casting AM Series Mg Alloys.

Higher pressure die casting (HPDC) AM series (Mg-Al-Mn) Mg alloys have wide application potential in the automobile industry. To promote its application, systematic investigation on the corrosion performance and corrosion residual strength of HPDC AM50+1Ce and AM60 was carried out. The corrosion of HPDC AM50+1Ce was more uniform, while the pitting corrosion of AM60 was more severe, and the mechanical properties of HPDC AM60 was more sensitive to corrosion. The residual strength of AM50+1Ce and AM60 after corrosion of 648 h was 199 MPa and 183 MPa, respectively. The findings can contribute to a better understanding of the corrosion and residual strength of HPDC AM series Mg alloys.

On the role of Laves phases on the mechanical properties of Mg-Al-Ca alloys

As-cast Mg-Al-Ca alloys are among the most promising alloys for elevated temperature applications (≤200 °C) due to their superior creep properties when compared to conventional AZ or AM series Mg alloys. The microstructures of Mg-Al-Ca alloys consist of a soft α-Mg phase reinforced with hard interconnected Laves phases. These interconnected Laves phases are the main reason for the good creep resistance of these alloys as they impede creep deformation. The volume fraction, type and morphology of Laves phases can be controlled through the Ca/Al ratio. Consequently, the Ca/Al ratio can be used to manipulate the mechanical properties of this alloy system in order to achieve optimum creep resistance. We show here that a higher Ca/Al ratio results in i) higher volume fraction of intermetallic Laves phases in the microstructure, ii) improvement in the yield strength (YS), and iii) enhancement in creep resistance at a stress level of 50–70 MPa and a temperature of 170 °C of the as-cast alloys. Moreover, the local strain distribution and partitioning at the microstructural level occurring during high temperature tensile deformation (at ∼170 °C) was measured using quasi in-situ DIC in SEM revealing stress localisation at the α-Mg Laves phase interfaces.

Wear and machinability of AM series magnesium alloys

Abstract This study deals with the effect of different quantities of aluminum (Al) on the wear resistance and machinability in AM series cast magnesium alloys. Changes in the quantity of Al in these alloys (containing 0.5 wt.-% Mn) and their effect on hardness, wear resistance and machinability with respect to cutting force were analyzed. To this purpose, AM series cast magnesium alloys (AM20, AM40, AM60, and AM90) in varying amounts of Al from 2 to 9 wt.-% were used. It was observed that the intermetallic phases Mg17Al12 and Al8Mn5 found in the microstructure had an effect on their wear resistance, hardness and machinability (with respect to cutting force), flank build-up, chip formation and surface roughness. AM90 alloy manifested the highest values in terms of hardness, wear resistance and surface quality among these alloys. On the other hand, AM90 alloy had the lowest machinability properties.

Influence of Al content on machinability of AM series magnesium alloys

Influence of Al content on machinability of AM series magnesium alloys

Diversidad genética de accesiones de la familia Caricaceae en el sur de Ecuador

The genetic diversity of 78 accessions of the Caricaceae family collected in the provinces of Azuay, Canar, Loja, El Oro and Zamora Chinchipe, south of Ecuador, was studied, including the species Vasconcellea candicans, V. goudotiana, V. longiflora, V. microcarpa, V. monoica, V. omnilingua, V. palandensis, V. stipulata, V. parviflora, V. sp., V. x heilborne, V. x heilborne cv pentagona, V. x heilborne cv chrysopetala, Carica papaya, Jaracatia digitata y J. spinosa by DNA amplifications using 14 aleatory primers from AA, AC, AM and AN series of Operon Technologies Inc. The used RAPD primers produced 76 polymorphic fragments with sizes between 368 and 2102 base pairs (bp). The cluster and principal coordinate analysis grouped the accessions of each kind among them and the results were consistent with previous studies. The dendrogram separated clearly the three genera, however, based on these results, studies and morphological observations, the creation of a new genera that groups the Vasconcellea candicans accessions is suggested. Furthermore, the authors support the hypothesis of designating the materials collected in the Molleturo zone as a new taxon of the genera Vasconcellea. As in other studies, the results suggest possible events of interspecific hybridization within Vasconcellea genus.

Flood frequency analysis for a braided river catchment in New Zealand: Comparing annual maximum and partial duration series with varying record lengths

This study addresses technical questions concerning the use of the partial duration series (PDS) within the domain of flood frequency analysis. The recurring questions which often prevent the standardised use of the PDS are peak independence and threshold selection. This paper explores standardised approaches to peak and threshold selection to produce PDS samples with differing average annual exceedances, using six theoretical probability distributions. The availability of historical annual maximum (AMS) data (1930–1966) in addition to systemic AMS data (1967–2015) enables a unique comparison between the performance of the PDS sample and the systemic AMS sample. A recently derived formula for the translation of the PDS into the annual domain, simplifying the use of the PDS, is utilised in an applied case study for the first time. Overall, the study shows that PDS sampling returns flood magnitudes similar to those produced by AMS series utilising historical data and thus the use of the PDS should be preferred in cases where historical flood data is unavailable.

The Influence of Al Content and Thickness on the Microstructure and Tensile Properties in High-Pressure Die Cast Magnesium Alloys

The influence of Al content and section thickness on the microstructural features and tensile properties of high-pressure die cast AM series magnesium alloys is quantified in order to better understand the relationship between microstructure and tensile properties. It is found that with increasing aluminum content, the yield strength increases and the ductility decreases. Increasing the plate thickness results in a decrease in both the yield strength and ductility. The grain size, β-Mg17Al12 phase volume fraction, and solute content are all quantified through the thickness of the plates. It is found that the plates have a skin with increased hardness, due to a fine grain structure. The primary factors affecting strengthening in these alloys, including microstructural variations through the thickness, are accounted for using a linear superposition model. We conclude that yield strength is dominated by grain boundary strengthening and solid solution strengthening effects. The through-thickness grain size and solute concentration were quantified and these variations were found to play an important role in controlling the yield strength of these alloys.

Hydrological Characteristics of Lower Nzoia Sub-basin in Kenya

This study sought to investigate hydrological characteristics of lower Nzoia sub-basin in Kenya. Trend (long and medium) utilized graphical and statistical approach. Extreme value (EV) analysis based on frequency, annual maximum flows, exceedance probability, low flows and probable maximum precipitation was used. Quality control showed consistency in rainfall, temperature and discharge datasets. Maximum-minimum monthly and annual flows and rainfall showed maximum flows centered in March-to-May (peak) with increasing temperature. Trends, seasonality and cycles were identified and maximum values in rainfall and discharge closely followed the pattern for peak rainfall seasons. Based on the flow magnitudes and 100-year return period, the upstream station (1EE01) had lower values compared to downstream station (1EF01) for different assumed distributions and thus 1EF01 assumed to be more reliable. Exponential and Pareto distributions indicated a normal tail and thus appropriateness of EV1/Gumbel distribution in calibrating AM series. Best conventional calibration results based on assumed distributions using EV1/Gumbel superimposed with the extreme value distribution fitted along with the exponential/Pareto Q-Q plots for comparison. Estimated maximum withdrawal in monthly terms for 1EE01 and 1EF01 was 262.5 and 368.4 cumecs respectively. Analyses of low stream flow indicate probable availability of water in streams at different return periods.

Advanced Materials Series, Wiley-scrivener

The Advanced Materials Series (AM series) published by Wiley-Scrivener Publishing, USA has comprised about 30 volumes till 2016. This series intends to provide recent advancements of the fascinating field of advanced materials science and technology, particularly in the area of structure, synthesis and processing, characterization, advanced-state properties and applications. The volumes cover theoretical and experimental approaches of molecular device materials, biomimetic materials, hybrid-type composite materials, functionalized polymers, supramolecular systems, information- and energy-transfer materials, bio based and biodegradable or environmental friendly materials. Each volume is devoted to one broad subject and the multi-disciplinary aspects are drawn out in full. Each volume is comprehensive and represents the cutting edge of science. They are written for a broad readership including researchers and students from diverse backgrounds including chemistry, physics, materials science & engineering, medical science, pharmacy, biotechnology and biomedical engineering.