Papers by Keyword: Mg Alloy

Abstract: Mg-Zn-Y alloys with long-period stacking ordered (LPSO) phases have superior strength at elevated temperatures. We studied plastic deformation and creep behavior of a Mg₉₇Zn₁Y₂ (at.%) alloy. Deformation kinking of the LPSO phase plays an important role in strengthening the alloy during compression at elevated temperatures. Growth stacking faults with Zn/Y segregation can act as obstacles to non-basal slip and deformation twinning in Mg matrix. The tensile creep strain was only about 0.01% under a tensile stress of 70MPa for 100h at 200 °C, demonstrating excellent creep resistance of this alloy. Generation and motion of basal dislocations led to bending of LPSO phase during tensile creep of the Mg₉₇Zn₁Y₂ (at.%) alloy. Plastic deformation in Mg grains was mostly achieved through basal slip during creep at temperatures below 200 °C, while non-basal slip through the generation and motion of “a + c” dislocations was activated with increasing the temperature to 200 °C and above. Dissociation of dislocations and Suzuki segregation on basal planes occurred widely in Mg matrix, which hindered dislocation motion and thus played an important role in preventing Mg grains from softening during deformation at elevated temperatures. In addition, Cottrell atmospheres were observed along dislocations in plastically deformed LPSO phase, impeding motion of dislocations. The superior strength and creep resistance of the Mg₉₇Zn₁Y₂ (at.%) alloy at elevated temperatures are thus associated with the LPSO phase, stacking faults in Mg grains, formation of Cottrell atmospheres in LPSO and occurrence of Suzuki segregation in Mg.

Abstract: The WE43 is a Mg-Y-Nd alloy that presents good mechanical properties and an high creep resistance. For these reasons currently is widely used in the aerospace and automotive industries. The setting of the right thermal heat treatment parameters plays a crucial role in determine the microstructure and consequently the mechanical properties of the alloy. With this in mind, the main goal of this work has been that to identify the optimal parameters to achieve a high impact resistance and at the same time, the most suitable choice, to reach also an important cost-saving solution, which is extremely important especially from the industrial point of view.

Abstract: The high-tech method of creating anticorrosion calcium phosphate coating on the magnesium alloy MA8 (MgMnCe) has been developed. As was demonstrated by the volumetry method the sealing of the layer formed on the surface of Mg alloy using plasma electrolytic oxidation by superdispersed polytetrafluoroethylene substantially reduced the rate of the corrosion process. Here, the surface of the calcium phosphate layer containing hydroxyapatite (Ca/P = 1.61) remains biologically active. Studies of architectonics of the surface of innate immune cells have been performed in vitro.

Abstract: Biodegradable implant material for medical applications has to fulfill specific therapeutic tasks. For our investigations, synthetic polymers, polyurethanes (PUR) and polyetherimide (PEI), were used. Both systems have been used to coat an Al-free Mg alloy. Characterization of materials was performed by IR, spark spectral analysis, microscopy and EIS. Electrochemical investigations of the different treated samples in aqueous NaCl and Hank's Balanced Salt Solution indicate specific response of the polymer/substrate system to corrosion attack.

Abstract: After 5% lithium was added to AZ31 magnesium alloy, the alloy was extruded at 380^oC with the extrusion ratio of 101. Mechanical responses and microstructure evolution were investigated. The microstructure and texture evolution were examined by electronic backscattered diffraction (EBSD) and X-ray diffraction (XRD). Tensile tests in the tensile directions of 0^o, 45^o and 90^o were carried out at room temperature. Lithium addition brought about the strong divergence of the grain orientation and triggered the spread of the (0002) basal texture. The room temperature ductility of the extruded Mg alloy sheets was improved due to the tilted weak basal texture.

Abstract: AZ31 magnesium alloy and its alloy with 5% lithium were extruded to 1mm in thickness sheets at 380 ^oC with extrusion ratio of 101. Microstructure evolution and mechanical behavior of the extruded Mg alloy sheets were examined. The microstructure and texture evolution were investigate by electronic backscattered diffraction (EBSD) and X-ray diffraction (XRD). Mechanical performance was carried out by tensile tests at room temperature. In addition, the evolution of neutral layer and microstructure was also examined by V-bending. It was found that Li addition resulted in the strong divergence of the grain orientation. (0002) basal texture of AZ31 alloy sheets with 5% lithium has been weakened. The room temperature ductility of these textural sheets was enhanced owing to the tilted weak basal texture. Moreover, it exhibits superior ductility during V-bending process at room temperature.

Abstract: In the super-long life regime, the fatigue behavior of as-extruded Mg-6wt%Zn-xY-0.8wt%Zr Mg alloys with Y content of 0, 1, 2 and 3 wt% have been investigated, respectively. The result indicated that for all measured S-N curves, a plateau existed in the regime of 5×10⁶-10⁸ cyc, and then the fatigue strength gradually decreased between 10⁸ and 10⁹ cycles. Therefore, only fatigue strength corresponding to 10⁹ cycles can be determined. Compared with other alloys, the alloy with Y content of 2 wt% has the highest fatigue strength and its value is 105 MPa. SEM observations to fracture surfaces revealed that for all alloys, the fatigue crack mostly initiated at the surface or subsurface of samples failed within 10⁶-10⁹ cycles. Further observation indicated that the crack initiation was related with activated slip bands instead of phase particles and activated twins. Based on the measured results and Murakami equation, it demonstrates that the fatigue strength of alloys is more dependent on the hardness values.

Abstract: The contribution is dealing with suggestion of tool geometry affecting weldability of Mg alloy AZ31B at friction stir welding. Four welding tool made of tool steel H13 (X40CrMoV5-1) with different geometry have been used at welding. Weld joints with high quality have been performed at following parameters: tool revolutions 600 rpm, welding speed 40 to 120 mm/min, angle of inclination 3° and pressure force 38 kN. Area of weld metal accounted fine-grained structure with average dimension of grain 13 μm. Structure is formed by solid solution α - Mg, Al-Mn particles and compound MgAl₃Mn₂. Strength of weld joint reaches value 265 MPa. Fracture areas accounted character of ductile fracture.

Abstract: Contribution deals with soldering of Mg alloy AZ31B by ternary solder ZnAl6Ag6 with ultrasonic support. Suggested solder has been analyzed from many aspects. Microstructure of solder consistutes of solid solution α-Al (FCC_Al), β-Zn (HCP_Zn) and intermetallic phases AgZn₃ and AlAg₃. Melting temperature of solder 386.8 °C has been determined by DSC analysis. Metallurgical process of ultrasonic soldering has run at 410 °C for 3 s. Soldered joint has been constituted by eutectic ternary structure β-Mg₁₇(ZnAl)₁₂, solid solution α - Mg, which contains Al and Ag elements. At solder-substrate interface, there has been formed intermetallic phase Mg₂Zn₁₁. The highest value of microhardness has been 260 HV. To predict lifetime of soldered joint, calculations in software Thermo-Calc has been performed.

Abstract: The need for structural materials in temporary implant applications has grown in the recent years; materials that provide short – term structural support and which can be reabsorbed into the body after healing are being sought. These are materials that are biocompatible and biodegradable. These constitute a novel class of bioactive biomaterials which are expected to support the healing process of a diseased tissue and to degrade thereafter. Magnesium alloys attracted great attention as a new kind of degradable biomaterial. Mg shows great promise as a potential biocompatible and biodegradable material in biomedical applications where it has gained the interest of researchers in the field. Biodegradable and bioabsorbable magnesium – based alloys provide a number of benefits over traditional permanent implants. There are however some disadvantages to the use of Mg alloys, one of the most critical being the release of hydrogen and alkalinization resulted from the corrosion of Mg. In connection to these drawbacks, a possible solution could be finding alloying elements which would contribute to the reduction of the corrosion rate in the human body. Studies show that a promising alloy for Mg, could be Calcium - a major component of the human bone and also an essential element in the chemical composition of cells. The present paper shall focus on the elaboration of Mg-Ca alloys, respectively Mg0,63Ca to Mg0,8 5 Ca, in the form of bars. These bars were obtained by cast in an inert atmosphere in the presence of argon, in order to be analyzed as biodegradable orthopedic implants. The structure of the alloy has been studied through SEM analyses, X-Ray diffraction, and EDAX to determine the chemical composition, as well as the distribution of elements in the structure. The main desiderate is finding an alloy which would have a minimum healing period postsurgery, pathophysiology and toxicology and a promising degradation behavior.