Papers by Keyword: Magnesium Alloy

Abstract: The microstructure, texture, and tensile properties of hot extruded Mg-6Zn-1Y-1Ce alloy obtained at a temperature range of 300 °C to 400 °C were studied. Electron back-scatter diffraction (EBSD) results revealed that strong basal plane texture was found along extrusion direction in the sample extruded below 340 °C due to discontinuous dynamic recrystallization (DRX) mechanism. In the sample extruded at 340 °C the average value of Schmid factor (SF) of {0001}〈11-20〉 slip system was 0.09. However, the sample extruded above 370 °C had weak basal texture under the control of continuous DRX mechanism, and the SF was well-distributed with an average value of about 0.32. The strengths of as-extruded samples decreased with increase of extrusion temperatures. In addition to fine grain strengthening, texture strengthening had a significant contribution to the high strength for the sample extruded at low temperature.

Abstract: Friction Stir Back Extrusion (FSBE) is a new grade of severe plastic deformation process capable of producing metallic tubular geometries that exhibit ultrafine grain structure and superior mechanical properties. FSBE of tubular sections provide opportunities for producing lightweight rigid structures for the automotive, aerospace and construction industries. This research investigates the effect of submerging conditions (in water at 25 °C and 2 °C) for Magnesium AZ31-B tubes on the grain size, mechanical properties, temperature history and power consumption. Submerged FSBE is compared to FSBE in air at fixed process parameters of 90 mm/min and 2000 rpm. It is shown that the impact of submerging is statistically insignificant in terms of the mechanical properties, ultimate tensile strength and percent elongation, of the produced tubes according to the conducted t-tests. On the other hand, the optical microscopy results indicated finer grains at the inner wall of the seamless tubes for FSBE in air and underwater FSBE at 25 °C when compared to underwater FSBE at 2 °C.

Abstract: Magnesium and its alloy have good characteristics for implant materials. Increasing these characteristics is needed to be an excellent material. The objective of this research is to investigate the magnesium alloy AZ31 (Al: 3.07%; Zn: 1.05%) characteristics affected by thermal oxidation temperature. Investigated characteristics in this study were hardness, corrosion resistance, and microstructure. The temperature variations of thermal oxidation were 100, 200, 300, 400 °С. The Vickers micro-hardness decreased with increasing of thermal oxidation temperature and the as-received of Mg alloy had the highest Vickers micro-hardness. The lowest corrosion resistance occurred at 200 °С of thermal oxidation temperature but this corrosion resistant was higher than that at the as-received material. The microstructures of Mg alloy were looked cracked in their grains at the thermal oxidation temperature over than 200 °С. The cracks increased by increasing of the thermal oxidation temperature.

Abstract: This paper presents an experimental investigation of the mechanical response and failure mode of magnesium alloy-based Fibre Metal Laminates (FMLs) having different surface pretreatments under axial compression loading conditions. To improve the interfacial bonding strength between the metal and composite layers, three categories of samples were fabricated by hot pressing using sandblasted, annealed and both sandblasted and annealed AZ31B magnesium alloy sheets. To evaluate the bonding strength along the shear and normal directions, single lap shear tests and T-peel tests were conducted. It was found that the combination of sandblasting and annealing can greatly enhance the shear and normal interfacial bonding strength compared with only sandblasting and annealing, separately. To assess the effect of the interfacial bonding strength on the FML compressive performance, quasi-static buckling tests were performed at varying surface treatments of the magnesium alloy sheets. The analysis of the load-stroke curves and failure modes indicates that delamination can significantly reduce the buckling capability and structural stability, and that the improvement of interfacial bonding strength can dramatically strengthen the FML compressive capability.

Abstract: The development of light-weight materials and fabricating parts/sub-assemblies of substantially large dimensions has become a major issue for the aerospace industry, which has boosted the development of more advanced materials with high specification properties. Recent aluminum and magnesium alloys developments are based on achieving superior fatigue crack growth resistance, better corrosion resistance, lower density, etc. Standard manufacturing techniques, such as extrusion, ought to be developed in order to find a beneficial solution allowing for structural weight reduction, which is a very efficient means of improving aircraft performance. It is associated with the problem of extrusion profiles with a complex cross-section shape. In this work the formability of aluminum and magnesium alloys in the extrusion process was determined by the upsetting test through specification of the flow stress in relationship to the deformation size and rate. The results of the upsetting test of Al (7075, 2024, 8090, 2099) and Mg ( AZ31, AZ61, AZ80, WE 43) alloys were used in determining the conditions of the extrusion of profiles of various cross section shape and extrusion ratio. The analysis of macro and microstructure of extruded products and their mechanical properties demonstrates strong influence of the shape of extrudate cross section on metal exit speed and extrusion force value. Macro-and microstructure of all the investigated alloys after extrusion are highly homogeneous in terms of the grain size and morphology of the phase components, compared to the macro- and microstructure in the initial state, which justifies the use of them in production of aviation profiles.

Abstract: The potential of KOBO unconventional extrusion of metallic materials based on phenomenon of changing the path of plastic deformation with use of cyclic oscillation of the die by given angle and frequency has been presented in this paper. This process is used to change material properties by fragmentation of grains without preheating the billet and press parts with significantly lower extrusion force in comparison to conventional process. Various types of billets (various metallic materials in the form of: solid initial material, condensed chips, layered composite material) were used during the experimental tests to analyze the plastic flow of the material and the possibility of plastic deformation of various metallic materials such as aluminum alloys, magnesium alloys and copper in order to obtain a product with a complex shape in the KOBO process, using dies with different geometries. Mechanical properties, microstructure, scheme of plastic flow and extrusion force were examined during experimental work. KOBO extrusion can be considered as a more cost-effective process than conventional extrusion.

Abstract: This research characterized the strain hardening behavior of AZ31 under different stress states from shear to balanced biaxial tension with a newly proposed yield function. Experiments are conducted for AZ31 magnesium alloy by in-plane shear specimens, dogbone specimens, notched specimens and bulging specimens to characterize the flow behavior under different stress states. The flow behaviors are characterized by a newly proposed yield function in a form of the three stress invariants. The proposed yield function is implemented into ABAQUS/Explicit to predict the plastic response of the alloy under different stress states. It is shown that the proposed yield function can precisely predict the distinct flow behaviors and reaction forces from shear to equibiaxial tension from the initial yielding to fracture.

Abstract: Magnesium (Mg) alloy sheets are expected to be used as light-weight materials for structural components because of their low density and high specific strength. However, their press formability at room temperature is poor due to the strong crystal anisotropy of the hexagonal structure and the strong basal texture especially observed in AZ series rolled Mg alloy sheets. Recently, ZX series Mg alloy sheets have been developed that weaken the basal texture, thus improving press formability at room temperature. Although the plastic deformation behavior of ZX series Mg alloy sheets should be different notably from that of AZ series Mg alloy sheets, it is not substantially understood yet. In the present study, the work-hardening behavior of a rolled Mg-1.5mass%Zn-0.1mass%Ca (ZX10Mg) alloy sheet under monotonic and reverse loadings was investigated in detail experimentally. The microstructures of prestrained samples were also measured by means of EBSD measurements. Under monotonic tension, the stress in the rolling direction is higher than that in the transverse direction. A plateau region appears only in the transverse direction. Under monotonic compression, plateau regions appear in both the rolling and transverse directions. The in-plane anisotropy is less pronounced than that under tension. Under reverse loading from compression to tension, a sigmoidal curve appears during tension regardless of the loading direction. The sigmoidal trend depends strongly on the loading direction. The mechanisms that induce the abovementioned anisotropic deformation are discussed in terms of the difference in twinning and detwinning activities.

Abstract: The investment casting into a ceramic shell of magnesium alloys brings several difficulties, one of which is the high reactivity of some magnesium alloys with the often-used ceramic shells. In the group of these potentially problematic alloys belong the AZ91 magnesium alloy too. This paper aims to describe the interaction of magnesium melt with ceramic shell, especially from the point of view of manufacturing problems on the surface of emerging defects with reduced corrosion resistance. Samples of AZ91 magnesium alloy castings in as-cast and heat-treated were microstructurally evaluated. Surface defects were analysed using light and scanning electron microscopy, including their EDX chemical microanalysis.

Abstract: In this article, the possibility of using investment casting technology to produce high-quality shaped and thin-walled castings of magnesium alloys (Mg-Al based alloy - AZ91E and Mg-Zr-based alloy WE43B) at ALUCAST s.r.o. (the Czech based precision castings foundry) is described. The paper briefly focuses on using suitable and available protective atmospheres for the safe processing of magnesium alloys, considering the current European legislation. The casting process and the best arrangement of the gating system were optimized by software simulation of the casting process using "ProCast" software by the ESI group. Microstructures and mechanical properties of magnesium alloys AZ91E and WE43B within the scope of this article were investigated by light microscopy (LM), hardness tests, and tensile tests. In addition, radiography inspections and chemical composition analyses were performed. The experiments show that good mastery of magnesium melt processing technology (including knowledge of methods for reducing reactions between melt and ceramic shell, the porosity of real castings around 0.04%, etc.) allows high quality and precise magnesium castings with high mechanical properties corresponding to castings from AZ91E and WE43B alloys produced by sand casting.