AM50 Alloy Research Articles

Porosity quantification for ductility prediction in high pressure die casting AM60 alloy using 3D X-ray tomography

Porosity plays an important role in determining the ductility in magnesium alloy high pressure die castings. In this work, X-ray Tomography (XRT), fractographic analysis and Digital Image Correlation(DIC) have been implemented to understand the inter-relation between various pore characteristics, specifically porosity spatial distribution and morphology, and the ductility in thin-wall AM60 alloy high pressure die casting. The results show that a great amount of porosity was detected in the 20 studied samples. The pore size follows the three-parameter lognormal distribution. Among the detected porosity, small porosity (equivalent diameter ≤90 μm) is numerically dominant and the proportion in number reaches up to ~80%, which constitutes ~50% of the volume of porosity. In comparison, the large porosity (equivalent diameter >425 μm) accounts for a very low percent of the porosity population, namely ~1%, and only occupies ~5% of the volume of porosity. For through-thickness distribution of porosity, two defect bands were observed consisting of concentrated porosity. A great amount of pores randomly distributed pores in the skin and core, and some large pores (equivalent diameter >425 μm) are presented in the core. In addition, along tensile axis, heterogeneous porosity distribution is displayed in terms of local porosity and pore size. Tensile test coupled with DIC measurement has been conducted for the twenty samples with XRT data and the influences of various parameters of pore, including local porosity, size and position of pore, on the ductility have been analyzed. It can be seen that the local porosity in the fracture segment plays the primary role in determining the ductility, although the location and size of pore have effect on deformation heterogeneity and thereby affect the ductility. Therefore, the ductility can be considered as a function of the local porosity in the fracture segment. Moreover, though it's difficult to obtain the local porosity in the fracture segment prior to tensile test and the ductility can't be predicted based on it, there is a clear correlation between the elongation and the highest local porosity in the gauge, which can be got before tensile test, and thus ductility can be estimated accordingly.

Influence of cryogenic treatment on the corrosion of AZ91 and AM60 magnesium alloys in an isotonic solution

Abstract Biodegradable stents made of magnesium alloys have become revolutionary in the cardiovascular area. However, rapid corrosion in a body fluid environment is harmful to the mechanical properties and stability. In this study, untreated and cryogenically treated samples of AZ91 and AM60 alloy were employed at −196 °C for 48 h. Afterwards, the corrosion performance of the AZ91 and AM60 samples was tested in an isotonic solution containing 0.9 wt.-% NaCl. Electrochemical methods such as open-circuit potential measurement (OCP), potentiodynamic polarization, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion performance. In general, the results obtained for the electrochemical studies show that the cryogenically treated AZ91 and AM60 samples maintain superior corrosion resistance when compared to the former sample. The OCP results indicated that the cryogenically treated AZ91 and AM60 outperformed untreated samples after 1 h. The potentiodynamic studies confirmed that cryogenically treated AZ91 and AM60 had superior anodic pitting potential (Epit) and that the passivation zone is higher than AZ91 and AM60 when untreated. The EIS confirmed the lower corrosion kinetics for AZ91 and AM60 treated in the former sample.

Investigation of Localized Corrosion Phenomena in Selective Laser Melted 316L Stainless Steel

Selective laser melting (SLM) refers to the additive manufacturing of bulk material from powder on a layer by layer basis through melting via laser and rapid solidification. In recent years, additively manufactured metallic alloys produced by SLM have garnered attention due to opportunities in waste reduction, time and cost efficiency, and fabrication of geometrically complex structures. However, limited work has been performed to investigate the corrosion properties of these alloys. Understanding these mechanisms is crucial in assessing the attendant risks associated with the use of AM alloys in engineering design. Stainless steels such as 316L produced by SLM have presented advantages due to the corrosion resistant properties of these alloys. However, the non-equilibrium microstructure in these SLM materials, significantly different from that of the wrought counterpart, result in heterogeneities that may lead to localized corrosion such as melt pool boundary attack. A point of concern in stainless steels is intergranular corrosion due to the formation of secondary phases such as chromium carbides that deplete chromium from grain boundaries when the material is exposed to temperature ranges of 450 – 800 °C. While low-carbon steels such as 316L have great resistance to deleterious chromium carbide precipitation, this phenomenon has not been investigated in great detail in the case of selective laser melted 316L. However, it has been shown that precipitation of secondary phases is accelerated in SLM alloy systems such as Inconel 625 with respect to the wrought counterpart. Intergranular corrosion can ultimately lead to intergranular stress corrosion cracking, a form of brittle failure. This study investigates localized corrosion phenomena such as melt-pool boundary attack and intergranular corrosion and the associated microstructure-based mechanisms in the corrosion of these SLM 316L alloys. Galvanostatic etching, potentiodynamic scans through the double-loop potentiokinetic reactivation method, and mass-loss testing of wrought and SLM 316L are utilized to reveal the electrochemical behavior of these alloys. Additionally, focused ion beam and transmission electron microscopy are utilized to understand the microstructural origins of the observed corrosion phenomena.

Effects of 1WT.% Ti, In, and Sn Additions on the Microstructure, Mechanical and Corrosion Properties of the As-Cast and Hot-Rolled AM60 Magnesium Alloys

We study the influence of 1 wt.% Ti, In and Sn additions on the microstructure, mechanical properties and corrosion resistance of the as-cast and hot-rolled AM60 magnesium alloys. The analysis of microstructure was performed by using optical and scanning electron microscopes The phase composition of the alloys and grain sizes are analyzed. We also determine the ultimate strength, yield limit, relative elongation, and corrosion resistance of the alloys. The efficiency of alloying of AM60 alloy with titanium and tin (for the improvement of the mechanical characteristics) and with indium (for the improvement of corrosion resistance) is demonstrated.

Effect of Lubricant and Operation Temperature on the Metallurgical Property of AM60 Magnesium Alloy in ECAP Process

In this study, the effect of the lubricant type and operating temperature on the process of equal channel angular pressing (ECAP) for magnesium alloy AM60 was investigated. For this purpose, designed experiments were conducted in a rounded cavity die with a channel angle of 90° at three different operating temperatures using two lubricants including graphite and molybdenum disulfide. Then, the apparent qualities, microhardness, microstructure of the samples, and variation in the process force were analyzed. Findings revealed that using the molybdenum disulfide as a lubricant at high temperature reduces damage to the workpiece and the process force. However, the ECAP process increases the hardness of the processed samples and the hardness is almost the same in different modes of lubrication. Moreover, at lower temperatures, the hardness of the samples is higher. The microstructure of the samples demonstrated that molybdenum disulfide lubricant leads to finer grain size and a higher level of alignment than lubrication using graphite. At higher temperatures, dynamic recrystallization occurs during deformation, leading to the formation of ultrafine equiaxed grains in some regions of the microstructure.

High strength AM50 magnesium alloy as a material for possible stent application in medicine

ABSTRACTStents made of stainless steel are usually permanently placed in the treated area even after recovering from the disease which can cause problems like in-stent restenosis and thrombosis. A biodegradable stent temporarily opens vessels for remodeling and afterward, it is absorbed. Magnesium is suitable for such application, however, it is limited by its high corrosion rate. Especially iron negatively affects corrosion properties. Manganese as an alloying element can trap iron impurities. In this work, AM50 magnesium alloy was studied in the form of wires. The aim was to find main connections between microstructure, mechanical and corrosion properties of presented materials and compare them with advanced magnesium alloys containing rare earth elements. Studied AM50 is characterized by the tensile yield strength of 258 MPa and elongation of 14%. The reasonable corrosion rate of 1.24 mm/y and good cytocompatibility of AM50 alloy predetermine this alloy as a suitable material for stent application.

Effects of alloying element and cooling rate on properties of AM60 Mg alloy

Magnesium and its alloys have become important structural materials in the last couple of decades due to their exceptional and mechanical properties. In this study, the effects of the introduction Cd, Bi, and Sn alloying elements were introduced into AM60 alloys produced from Mg–Al–Mn triple junction in order to improve the microstructural and mechanical properties. The weight percent of the alloying elements was chosen as 0.5% wt besides the introduction of the additional alloying elements, the effect of cooling rate on microstructural and mechanical properties of the alloys have been investigated. The results showed that the alloying elements introduced to AM60 resulted in an improvement in the mechanical properties of the alloys, which is attributed to the changes in the microstructure. The higher cooling rate led to the formation of the finer α-Mg master matrix which in turn enhanced the mechanical properties of the alloys. It was observed that the intermetallic phase of β-Mg17Al12 at the grain boundaries became thinner due to the rapid cooling rate and the introduction of the alloying elements, and the continuity decreased and the intergranular distance shortened. The addition of the alloying element increased the tensile strength of the AM60 alloy from 140 MPa to 210 MPa and the elongation values increased from 5% to 22%. The effects of the alloying elements and the cooling rate on the hardness and yields properties of the samples were also studied.

Deformation response and microstructural evolution of as-cast Mg alloys AM30 and AM50 during hot compression

AbstractThe present study deals with the hot deformation behaviour of as-cast Mg alloys AM30 and AM50. The alloys have been investigated for mechanical and microstructural evolution in the temperature range 423–623 K and strain rate range of 10−3–10 s−1. A safe processing domain is identified for as-cast AM30 and AM50 alloys from the strain rate sensitivity map. The deformed microstructure of both AM30 and AM50 alloy reveals the occurrence of dynamic recovery and recrystallization for temperature above 523 K. Although the two alloys show similar behaviour in the hot deformation regime, they deviate at 623 K and low strain rate, where AM30 is fully recrystallized while AM50 attains necklace structure after deformation. This is likely due to the difference in the rate of dynamic recovery in the two alloys owing to the difference in Al concentration. Continuous dynamic recrystallization was the recrystallization mechanism active in the processing regime as deduced from the EBSD investigation.

Microstructure evolution and mechanical properties of friction stir welded dissimilar joints of as-extruded AM60 and AZ31 alloys

Two types of material positions, with AZ31 or AM60 in retreating side, were used for dissimilar friction stir welding in this study. The appearance, microstructure evolution, mechanical properties and fracture mechanism of the joints were investigated. The results showed that significant microstructure evolution occurred in the joint under the intense stirring and thermal cycling. Furthermore, the material positions had little influence on the appearance, tensile properties and failure locations of the joints. It is interesting that all the tensile joints fractured at the boundary of thermo-mechanically affected zone (TMAZ)/nugget zone (NZ) near the AZ31 side. In order to explore the fracture mechanism of the joints, the relationship of failure locations, microstructure and texture evolution of joints were analyzed. The analysis on EBSD demonstrated that the texture evolution in both TMAZ and NZ, as well as a certain extent of dislocation density and strain existing adjacent to TMAZ/NZ interface, was the main factor leading to the fracture at the boundary of TMAZ/NZ. The tensile strength of AZ31 alloy was smaller than that of AM60, the grain gradient and the second phases size near the NZ/TMAZ interface of AZ31 side were larger than those of AM60, resulting in the fracture tending to AZ31 side.

Effect of Boron on the Grain Refinement and Mechanical Properties of as-Cast Mg Alloy AM50.

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%.

Effect of extrusion welding locations on the corrosion of AM30 alloy extrudate

The effect of extrusion welding at three different locations on the corrosion of a magnesium alloy (AM30) extrudate after being immersed in 3.5% NaCl solutions for 1h, 12h, and 24h has been investigated. Different electrochemical methods namely, cyclic polarization, open-circuit potential, electrochemical impedance spectroscopy, and current–time measurements were employed. The corroded surfaces were characterized using various spectroscopic analyses. All electrochemical measurements confirmed that the corrosion of the Mg alloy extrudate changes depending on the location of the extrusion welding, which affects the values of the obtained corrosion current, corrosion rate, and corrosion resistance. The severity of corrosion was found to decrease with prolonging the exposure periods of time in the chloride solutions for all taken samples at the different locations of the extrusion welding. This was further confirmed by the scanning electron microscopy micrographs and the energy dispersive X-ray profiles taken for the corroded surfaces of the different extruded AM30 samples.

Protective Performance of Plasma-Enhanced Chemical Vapor-Deposited Ethyl Cyclohexane Coating on Magnesium Alloys

In the present investigation, plasma-polymerized ethyl cyclohexane (ECH) coatings were deposited onto AZ31 and AM50 magnesium (Mg) alloys using plasma-enhanced chemical vapor deposition. The influences of deposition time on the coating formation, surface morphology, chemical composition and electrochemical corrosion behavior were investigated. The coating deposition was confirmed by infrared spectroscopy (FT-IR), and the thickness was measured using a scanning electron microscope. Energy-dispersive x-ray analysis revealed an increase in carbon and a decrease in Mg concentrations as the coating duration was increased. Electrochemical impedance spectroscopy (EIS) results confirmed an improvement in the corrosion resistance of AZ31 and AM50 alloys due to ECH coatings in the presence of a 3.5 wt.% NaCl solution. Further, equivalent circuit curve fitting analysis of the EIS results indicated an increase in charge transfer resistance (Rct) values with longer coating durations. These results confirmed the protecting ability of ECH coatings against corrosive ion attack, which was also substantiated by the surface morphologies after corrosion. Impedance values decreased as the duration of exposure in a NaCl solution increased, and the coating prepared using a 30-min ECH deposition exhibited better protection properties.

Incorporation of halloysite nanotubes into forsterite surface layer during plasma electrolytic oxidation of AM50 Mg alloy

The increasing demand for high-performance lightweight metallic materials is driving an interest in Plasma Electrolytic Oxidation (PEO) as one of the most promising techniques for surface engineering of Mg. In order to enable smart and multifunctional performance, it can be beneficial to incorporate into ceramic PEO coatings nanocontainers to carry appropriate active and functionalising agents. In situ incorporation of nanocontainers is challenging since their integrity may be compromised by plasma discharge assisting coating formation. We studied incorporation of halloysite nanotubes (HNTs) as potential nanocontainers into forsterite, Mg2SiO4, formed during PEO processing of AM50 alloy at the frequency range of 100–5000 Hz. Detailed analysis of the coating microstructure, chemical and phase composition carried out by Scanning Electron Microscopy/Energy Dispersive X-ray Spectroscopy, Transmission Kikuchi Diffraction and X-ray Diffraction enabled evaluation of a pattern of surface temperature evolution during current pulses underpinning the PEO process. Transient analysis revealed that at pulses longer than 10−4 s, the surface heating becomes affected by the metal substrate acting as a heat sink. As the pulse duration approaches 10−3 s, raising surface temperature and increasing thermal gradients across the coating cause crystallisation of forsterite and grain growth towards the surface; this triggers thermally induced degradation and decomposition of HNTs adsorbed on the surface. In contrast, at short pulse durations (2 × 10−5 s), the energy released is insufficient to induce forsterite crystallisation and incorporated HNTs are retained in their original tubular structure. Due to the fine porosity and good structural integrity, such coatings show enhanced corrosion resistance in saline solution. Strong correlations between surface thermodynamic conditions and evolution of coating microstructure disambiguate the fundamental mechanisms underlying incorporation of nanoparticles into growing PEO coatings, thus creating the basis for efficient design of PEO processes and development of novel smart and multifunctional coatings with potential applications in many industrial sectors.

On the surface integrity of Electron Beam Melted Ti6Al4V after machining

The Additive Manufacturing process known as Electron Beam Melting (EBM) is increasingly used to produce Ti6Al4V biomedical parts, whose functional surfaces, however, need to be machined afterwards. The paper addresses the fundamental issue of surface integrity of EBM parts when subjected to machining operation under dry, flood and cryogenic cooling conditions. The machined surface integrity is evaluated in terms of microstructural and mechanical features, residual stresses, surface topography and defects. Results are then compared to the outcomes of the same machining tests carried out on the conventional wrought alloy. This study points out the different machinability of the two investigated alloys, highlighting that new insights into optimization of parameters for machining AM alloys are needed.

Effect of Sn Content on Heat Resistance of Mg-3%Al-1%Si Alloy for Casting

Magnesium alloys have the characteristic with high specific strength and lightweight property, it is widely used for auto mobile industry. Heat-resistant magnesium alloy is focused as a suitable material for weight reduction of the engine and power train parts in automotive field. In this study, microstructure and heat-resistant property in Mg-3mass%Al-1mass%Si (Mg-3%Al-1%Si) alloy with containing large amount of Sn (tin) were investigated. The alloys produced by permanent mold casting were investigated by optical microscope (OM), scanning electron microscopy (SEM) and measuring of bolt load retention at 423K. The heat-resistant property of Mg-3mass % Al-1mass % Si alloy with containing 6-13masss%Sn was higher compared with Sn free alloy and conventional Magnesium alloys (e.g. AZ91 and AM60 alloys).

Effect of Laser Welding Parameters on Porosity of Welds in Cast Magnesium Alloy AM50

Pores in the weld metal lower the mechanical properties of the weld. It is therefore important to understand the pore formation mechanisms and find procedures that could reduce porosity. This study ...

Characteristics of AlSi11-AM60 bimetallic joints produced by diffusion bonding

This paper demonstrates that the diffusion bonding method can be used to join AlSi11 alloy to AM60 alloy. The micro structure of the bonding zone in such joints was examined using optical and scanning electron microscopy. Its chemical composition was determined through energy dispersive X-ray microanalysis. The experimental results show that the microstructure of the bonding zone is dependent on the parameters of the diffusion bonding process. In an AlSi11-AM60 bimetallic joint fabricated at 420 °C, the bonding zone had a thickness of about 50 µm and it was composed of Mg-Al intermetallic phases with irregularly distributed Mg2Si phase areas. When the heating temperature was 440 °C, the bonding zone was about 150 µm thick. Mg2Si was the predominant phase and it was distributed more regularly over the Mg-Al phase matrix. The microhardness measurements of this joint showed that the bonding zone containing hard phases had much higher hardness than either of the alloys joined.

Research of the Cutting Possibility of Magnesium Alloys with Abrasive Diamond Wire Saw

Abstract Wire saw technology is a method that works great in industrial applications – it is a dominant method in the production of silicon wafers. But almost all kinds of brittle materials (ceramics, rocks, meteorite and minerals or wood) can be cut using wire saw. Question, this article will try to answer is whether this is also applicable to magnesion alloys? Article presents selected problems from an area of abrasive treatment of magnesium alloys. This includes effects of research, concerning possibilities of application of abrasive diamond wire in the process of cutting magnesium alloys AM60 and AZ91 as well as results concerning surface quality obtained after cutting with the abrasive diamond wire German Company HK Präzisionstechnik.

Numerical study of the behavior of magnesium alloy AM50 in tensile and torsional loadings

In this work, a numerical simulation of the behavior of the magnesium alloy AM50 in tension and torsion is performed. Preliminary experimental procedures were carried out in order to determine the material characteristics and the stress–strain response. Based on the experimental data, three material models were developed: linear elastic with isotropic plasticity, linear elastic with Johnson–Cook hardening and the Ramberg–Osgood model and their accuracy and computational time were investigated.

Workability Characteristics and Deformation Mechanisms of Die-Cast AM60 and AZ91 Magnesium Alloys: Correlation with Processing Maps

Thermo-mechanical deformation behavior of the die-cast AM60 and AZ91 alloys was assessed by performing uniaxial compression tests on Gleeble 3800 simulator under different temperatures and strain rate conditions. Low-temperature deformation behavior of both alloys was accessed at 25, 100, and 150 °C, at the strain rates of 0.1 and 1 s−1. Processing maps at a true strain of 0.5 were generated to study the intrinsic hot workability of AM60 and AZ91 alloys. Optimum processing windows were identified, and the evolution of microstructures and textures was correlated with the imposed deformation conditions. The processing map for the AM60 alloy exhibited three dynamic recrystallization (DRX) domains in the ranges: (1) 320-400 °C and 0.2-1.5 s−1, (1A) 300-325 °C and 0.1-0.2 s−1, and (2) 360-400 °C and 3-5 s−1. In Domain 1, DRX occurred predominantly by pyramidal slip and recovery mechanisms by cross-slip as confirmed by the randomized textures. Deformation in Domain 1A is by the combination of basal and prismatic slip. In Domain 2, dynamic recovery was a softening mechanism controlled by the climb. The processing map for AZ91 alloy exhibited two DRX domains in the ranges: (1) 260-310 °C and 0.1-0.5 s−1 and (2) 325-350 °C and 0.8-3 s−1. The rate-controlling mechanism was climb by lattice self-diffusion in Domain 1 and by grain boundary self-diffusion in Domain 2. Both alloys exhibited flow instability at 200 and 250 °C, and therefore, they were unsuitable for processing at these temperatures.