Papers by Keyword: Wrought Magnesium Alloy

Abstract: In recent years, the movement for banning the sale of gasoline cars and diesel vehicles, especially in Europe, and allowing only electric passenger cars has been accelerated. For examples, Germany’s federal council, the Bundesrat, has passed a resolution calling for a ban on combustion engine cars by 2030. If the ban were to go through, German citizens would only be permitted to purchase electric or hydrogen-fueled cars. In Norway, until 2025 there is a movement for legislation prohibiting the registration of new gasoline passenger cars and diesel cars. Beginning in 2025 in the Netherlands, a bill prohibiting the sale of new cars gasoline and diesel vehicles was submitted to Congress. Under the circumstances, the demand for light-weight products for automotive industries has increased due to global trends in environmental preservation. Although demands for magnesium has risen dramatically, production of magnesium alloy sheet still remains at a very low level. This study seeks to establish a guideline for roll design in the roll forming of wrought magnesium alloys to extend practical use of roll-formed products of wrought magnesium alloys. A three-dimensional elasto-plastic analysis by the finite-element method has been conducted to express exact roll-forming behavior of wrought magnesium alloys that have different stress-strain curves in tension and compression. Simple V-sections were formed by a tandem six-stand roll forming machine to demonstrate the effectiveness of the simulation methods with different stress-strain curves in the case of tension and compression. Also, spring-back analysis has been performed to investigate the exact cold roll-forming phenomenon for wrought magnesium alloy sheets.

Abstract: In recent years, the movement that banning the sale of gasoline cars and diesel vehiclesespecially in Europe and allowing only electric cars for passenger’s cars has been accelerated. Forexamples, Germany’s federal council, the Bundesrat, has passed a resolution calling for a ban oncombustion engine cars by 2030. If the ban were to go through, German citizens would only bepermitted to purchase electric or hydrogen-fueled cars. In Norway, until 2025 there is a movement tolegislation prohibiting the registration of new cars for passenger car gasoline and diesel cars.Beginning in 2025 in the Netherlands, a bill to prohibit the sale of new cars for gasoline and dieselvehicles was submitted to Congress. Under the circumstances, the growing demand for light weightproducts for automotive industries has been increased due to global trend of environmentalpreservation. Although requires of magnesium has risen dramatically, production of magnesium alloysheet remains still at a very low level in practical use. The aim of the study is to establish a guidelinefor roll design in the roll forming of wrought magnesium alloys to extend practical use of roll formedproducts of wrought magnesium alloys. A three-dimensional elasto-plastic analysis by finite elementmethod has been conducted to express exact roll forming behavior of wrought magnesium alloys thathave different stress-strain curves in tension and compression. A simple V-sections were formed by atandem six stands roll forming machine to demonstrate effectiveness of the simulation methods withdifferent stress-strain curves in the case of tension and compression. Also, spring back analysis hasbeen performed to investigate exact cold roll forming phenomenon for wrought magnesium alloysheets.

Abstract: Based on characteristics of direct extrusion for magnesium alloy seamless tube and continuous equal channel angular pressing (ECAP) of tubes, a new composite extrusion process of tubes including direct extrusion and many steps ECAP was invented firstly, which are shorten for TES process in this paper. A three-dimensional finite element thermo-mechanical coupled model and conditions for TES process were established. The extrusion process and cumulative strains evolution during TES process were simulated. The results show that TES process can improve the cumulative strains significantly. The microstructures observations of longitudinal sections for tubes fabricated by direct extrusion and TES process were carried out. It was found that when the extrusion temperature was 400°C, and extrusion ratio was 8.4 and the channel angle was 150°, TES process can refine the microstructures of tubes effectively.

Abstract: The microstructures, phase constitutions and mechanical properties of as-cast samples, extruded rods and plates of Mg-3.52Sn-3.32Al and Mg-6.54Sn-4.78Al alloys were investigated by optical microscopy, scanning electron microscopy, X-ray diffraction and mechanical testing. The results show that as-cast microstructure consists of α-Mg matrix, Mg₂Sn and a few dispersed β-Mg₁₇Al₁₂ phases. The two as-cast alloys exhibit good tensile mechanical properties. After hot extrusion, dynamic recrystallization occurs. Average grain size reaches 6 μm ~ 8 μm for rods, and a lot of fine micro-scaled particles exist, resulting in significant enhancement of tensile mechanical properties. The extruded Mg-3.52Sn-3.32Al rod exhibits better comprehensive tensile mechanical property than AZ31B alloy, with tensile strength σ_b of 295 MPa, yield strength of 200 MPa and elongation of 21.5% at ambient temperature. The extruded Mg-6.54Sn-4.78Al rod exhibits equivalent comprehensive tensile mechanical properties with ZK60 alloy, achieving tensile strength of 355 MPa, yield strength of 275 MPa and elongation of 11% at ambient temperature. The extruded plates at ambient temperature performed a tensile strength of 270 MPa.

Abstract: The hot deformation behavior of Mg-3.5Zn-0.6Y-0.5Zr alloy was investigated by compressive tests of strain rate ranges of 0.002~1 s^-1 and deformation temperature ranges of 300~450 °C using a Gleeble 1500D thermal simulator. The flow stresses in different deformation conditions are measured. The results show that flow stress is significantly affected by both deformation temperature and strain rate, the flow stress increases with increase in strain rate and decreases in deformation temperature during the hot compression process. The constitutive equation established on the basis of data of activation energy and stress exponent is a hyperbolic sine function.

Abstract: Based on finite element method, the FEA model used for analyzing fatigue properties of sample treated by laser shot peening (LSP) was established. In order to research the influence of material intensity on LSP effect, two kinds of wrought magnesium alloys AZ31B and ZK60 with different intensity were chosen as object, the compressive residual stress and fatigue life after LSP were analyzed. After spring back analysis the elastic strain is released in material inner, the value of compressive residual stress was reduced; after LSP with 3 times, the fatigue life gains of AZ31B and ZK60 were 105% and 163%, respectively. The results show that strengthening effect of high intensity material treated by LSP is better than that of low intensity material.

Abstract: The grain size and the distribution of crystal orientation have an important effect on the mechanical properties of wrought AZ31B magnesium alloy sheets. Because the AZ31B magnesium alloy sheets rolled by conventional rolling have a poor formability at room temperature, a new rolling technology of differential speed rolling is used to improve the mechanical properties of AZ31B magnesium alloy. The research shows that the number of twinning crystal decreases, the number of the core of dynamically recrystallized grain increases, and the grain size become fine and isotropy by differential speed rolling with the increase of the reduction and the improving of the rolling temperature to some extent. The differential speed rolling not only improves the isotropy of the basal texture and also improves the microstructure and mechanical properties.

Abstract: The influence of crystallographic texture on high cycle fatigue behaviour has been studied using an extruded rectangular profile of the AZ31 (Mg-Al-3wt%-Zn-wt1%) alloy. The fatigue samples, cut at 0, 45 and 90° to the extrusion direction correspond to different initial textures. Besides high cycle fatigue tests, quasi-static tensile and compression tests were performed to assess the tension-compression asymmetries as a function of the initial texture. The micro-mechanisms of fatigue crack initiation were investigated using scanning electron microscopy and electron backscatter diffraction. Differences in the mechanical properties and the endurance limit for the different sample directions are related to the initial texture and, subsequently, the easiness or difficulty of slip/twinning.

Abstract: The microstructures, mechanical properties, and formability of an Mg-1.5Zn-0.1Zr alloy with rare earth element of Erbium addition have been examined by using optical microscopy, scanning electron microscopy/energy dispersive X-ray spectroscopy, and thermal mechanical testing. The results showed that Erbium combined with Mg and impurity elements forming small particles dispersed on the matrix. Therm-mechanical simulation in the temperature range from 250°C to 400°C and strain rate from 0.1 to 1.0 indicated that the flow stress decreases with the increase of the temperature and the decrease of the strain rate. Sheet samples were prepared through ingot casting, hot rolling, cold rolling, and intermediate annealing. Remarkable grain size refinement was realized through recrystallization during the rolling process. Good combination of strength and ductility was achieved by applying intermediate annealing before the very last cold rolling. Further improvement of ductility and formability could be obtained by conducting proper heat treatment on the finishing cold-rolled sheets.

Abstract: The semi-solid AZ61 wrought magnesium alloy was fabricated by mechanical stirring method. Thixo-forging set-up were designed and made. The traditional forging and thixo-forging processes of AZ61 magnesium alloy were studied with both computer numerical simulation and experimental methods. The constitutive model of semi-solid AZ61 alloy was established in our prior literature. The differences between traditional forging and thixo-forging processes were analyzed. Results indicated that smaller load and uniform strain & stress were acquired in thixo-extrusion process. Simulation results were good agreement with experimental ones.