Results 1 - 10 of 4668
Results 1 - 10 of 4668. Search took: 0.029 seconds
|Sort by: date | relevance|
[en] An attempt is made to rationalize the effect of pre-strain history on fatigue behaviors of AZ31 magnesium alloy. Axial fatigue tests were conducted in the extruded and pre-compressioned AZ31 alloy under low cycle total strain control fatigue conditions. The pre-strain process influences the plastic deformation mechanism activated during fatigue deformation, especially during tensile loading, by enhancing the activity of detwinning mechanism. The low-cycle fatigue lifetime of extruded AZ31 alloy can be enhanced by the pre-compression process. And the hysteresis energy was successfully used to predict the low-cycle fatigue lifetime. (paper)
[en] Highlights: • Dynamic bio-corrosion test bench for simulating physiological flow environment in vitro was designed. • Effects of different corrosion media on the bio-corrosion rates of Mg alloy were reported. • Microstructures of the corrosion surfaces under static and dynamic conditions in different media were observed. • Quantitative relationships between the bio-corrosion rates of Mg alloy and flow velocities were determined. • Joint influence of flow velocity and corrosion medium on the bio-corrosion behaviors of Mg alloy was discussed.
[en] Highlights: • Mg-2wt%Zn shows an exceptionally good deformability at room temperature. • The strongest texture component eventually transformed from as-extruded basal to 〈101¯0〉 fiber. • The rotation processing of Mg lattices explains the cold-drawn deformation mechanism. We performed multiple-pass cold drawing for Mg-2wt%Zn alloy until 91% accumulative true strain, indicating an excellent drawing deformability of Mg alloy at room temperature. Based on texture analysis, the strong basal texture, which was formed during hot extrusion, was further strengthened at the initial stage of drawing. Subsequently, under the effect of twining and constrained inclined compressive stress, more slips were activated, leading to weakening of the basal texture and an evident drop in the maximum texture intensity. This process was associated with a rapid rise in microhardness and strength as well as a rapid decline in tensile elongation. At larger strain, non-basal slip systems were gradually activated. As a result, the maximum texture intensity gradually increase again, along with relatively smooth change in mechanical properties. The texture component eventually transformed from as-extruded basal texture to typical 〈101¯0〉 fiber texture with 〈101¯0〉 parallel to the drawing direction.
[en] There is a consistent demand for superior materials in every industry. The areas on demand are automobile and aerospace sectors in major.. The most commonly used material in these fields is Aluminium.Though it possess all the properties up to some extent constant demand is pushing for alternate materials. Dissimilar alloys have been a relatively new approach towards these fields.. Friction stir welding dissimilar alloys is a big leap in Automobile sector. In this paper a detailed review of Friction stir welding of Dissimilar Magnesium alloys has been done. This work will serve as a reference to subsequent researchers. (paper)
[en] ZM21 alloy has been one of the most suitable candidate materials for implant owing to its bio-compatibility properties. However, the rapid corrosion of ZM21 alloy has been an issue questioning its adaptability in bio-implant applications. In the present study, an effort was taken to address this issue by optimising the thermo-mechanical process on the ZM21 alloy. ZM21 magnesium alloy was subjected to varying temperatures hot rolling (250, 300 and 350 °C) with 75% reduction followed by subsequent short annealing at 200 °C for 10 min In-vitro tests and tensile test were performed to determine the bio-corrosion behaviour and mechanical properties of the thermomechanically processed ZM21 alloys. These results converged to a recommendation that ZM21 rolled at 350 °C and subsequent short annealing at 200 °C exhibits the best bio-corrosion resistance and biocompatibility owing to the effect of its coarser grain structure and lesser twin density than those obtained with other parameters. (paper)
[en] This paper presents the deformation behavior of commercial Mg-Al-Zn-Mn type alloys during hydrostatic extrusion process at elevated temperatures. In the current study commercial Mg-Al-Zn-Mn type alloys with different Al contents were subjected to hydrostatic extrusion process at a range of temperatures and at ram speeds of 4.5, 10 and 17 mm/sec. Under the hydrostatic condition at 518K, the alloy with Al contents of 2.9 wt% was successfully extruded at all applied speeds. The alloys with Al content of 5.89 and 7.86 wt% were successful up to 10mm/sec, and finally extrusion of alloy with Al content 8.46wt% was successful only at 4.5 mm/sec. These results show that the deformation limit in the Mg alloys in terms of extrusion speed greatly extended to higher value in the proximity of lower Al content. It is presumed that deformation becomes harder as Al content increases because of strengthening mechanism by solute drag to increase of supersaturated Mg17 Al12 precipitates. Also, microstructures of cast and extruded Mg alloys were compared. Defect-wide microstructure of cast alloy completely evolved into dense and homogeneous microstructure with equiaxed grains
[en] The primary aim of this paper was to evaluate several probabilistic fatigue crack propagation models using the residual of a random variable, and to present the model fit for probabilistic fatigue behavior in Mg Al Zn alloys. The proposed probabilistic models are the probabilistic Paris Erdogan model, probabilistic Walker model, probabilistic Forman model, and probabilistic modified Forman models. These models were prepared by applying a random variable to the empirical fatigue crack propagation models with these names. The best models for describing fatigue crack propagation models with these names. The best models for describing fatigue crack propagation models with these names. The best models for describing fatigue crack propagation models with these names. The best models vor describing fatigue crack propagation behavior in Mg Al Zn alloys were generally the probabilistic Paris Erdogan and probabilistic Walker models. The probabilistic Forman model was a good model only for a specimen with a thickness of 9.45mm
[en] A Mg-23.3wt.%Ni eutectic alloy was prepared by the process of hydriding combustion synthesis followed by mechanical milling (HCS+MM). The product showed a high hydriding rate at 373 K and the dehydrogenation started at temperature as low as 423 K. Several reasons contributing to the improvement in hydrogen storage properties were presented. The result of this study will provide attractive information for mobile applications of magnesium hydrogen storage materials, and the process of HCS+MM developed in this study showed its potential for synthesizing magnesium based hydrogen storage materials with novel hydriding/de-hydriding properties. (authors)
[en] The interfacial properties of ZnO(0001)/Mg(0001) and ZnO(000)/Mg(0001) interfaces were investigated by theoretical calculations. It shows that the ZnO(000)/Mg(0001) interface, with Mg atoms on the top of first layer O atoms of ZnO surface slab (OT site), has the lowest interface energy, and even lower than the interfacial energy of α-Mg/Mg melt (0.1 J m−2). Considering interfacial energy and interfacial electronic properties, the calculated results and corresponding analysis support the heterogeneous nucleation potency of ZnO particles for α-Mg grains of magnesium alloys. (paper)
[en] In order to develop new magnesium alloy sheets with a good balance between ductility and stretch formability at room temperature, here we designed an Mg alloy with dilute Sn and Y and investigated the microstructure, texture, mechanical properties and stretch formability of Mg-0.4Sn-0.7Y in wt% (TW00) alloy compared with AZ31 alloy under extrusion and hot rolling-annealing conditions. We found that, after extrusion, the extruded TW00 (TW00-E) sheet exhibited a more homogeneous complete dynamic recrystallized microstructure and a splitting texture character with ~20Â° tilted to the extrusion direction, compared with the extruded AZ31 (AZ31-E) sheet. After hot rolling-annealing at 400 Â°C, both the hot rolled annealed TW00 (TW00-RA-400) and AZ31 (AZ31-RA-400) sheets presented similar complete static recrystallized microstructures. However, significant texture weakening occurred in the TW00-RA-400 sheet rather than the AZ31-RA-400 sheet, due to static recrystallization induced by twins and grain boundaries. Tensile tests revealed that the TW00-E and TW00-RA-400 sheets with high Schmid factor (SF) for basal slip exhibited high ductility (~ 33% and ~ 32%). Simultaneously, prismatic slip and texture weakening played a significant role on decreasing r-values for the TW00-E and TW00-RA-400 sheets, respectively, which contributed to the improvement in stretch formability (~ 6.2 mm and ~ 5.4 mm) at room temperature. Therefore, we concluded that the TW00 alloy provided a bright prospect to achieve a good balance between the ductility and stretch formability at room temperature via extrusion or hot rolling-annealing.