Papers by Keyword: AZ31 Alloy

Abstract: Titanium, zirconium and magnesium alloys are considered to be biocompatible, and can be used as implants such as hip ball and sockets and to make medical equipments. Biomaterials with hybrid structures in some applications utilizing the beneficial properties of different metals together are considered potential implant materials. Therefore, in this study, experimental trials were attempted to bond pure magnesium, AM60 (6 wt% Al-0.27 wt% Mn), and AZ31 (3 wt% Al-1 wt% Zn) alloys to pure zirconium and Ti6Al4V (6 wt% Al-4 wt% V) alloy to experimentally evaluate the forming bimetallic structures by diffusion bonding technique by vacuum hot pressing. SEM analysis showed the presence of a significant diffusion zone and a presence of diffusion bonding in some metallic couples. It may be suggested that novel hybrid implant materials, composed of diffusion couples of magnesium, zirconium and titanium alloys may emerge in the future.

Abstract: Uniaxial hot compression tests were performed at constant temperature (T) and strain rate (ε& ) in the ranges of 200-500 °C at an interval of 50 °C and 0.001-20 s-1. The flow stress data were used to develop the extrusion limit diagram for AZ31 and AM30 magnesium tubes. The extrusion limit diagram shows a wide region available for extruding AZ31 and AM30 seamless tubes, and comparison of the two extrusion limit diagrams shows that, the extrudability of AM30 alloy is better than that of AZ31 alloy. Actual extrusion trials validated the predicted temperature rise limit curve corresponding to the occurrence of surface cracking during the extrusion process. Magnesium tubes were successfully extruded according to the safe regions identified by the extrusion limit diagram.

Abstract: Microstructure and tensile properties of AZ31 rolled at different temperatures were characterized. Rolling of extruded AZ31 plates was carried out at room temperature, 573K, 623K and 673K. Cold rolling of extruded AZ31 plates was difficult due to the poor formability at room temperature. And deformation twinning plays an important role in rolling of AZ31 alloy at room temperature. The microstructural analysis showed that the nucleation of dynamic recrystallization (DRX) occurred at 573K, DRX was almost completed at 623K and grain growth was determined at 673K. The ultimate tensile strength (UTS) as large as 377MPa was achieved after rolled at 573K. And the anisotropy in strength was obviously examined due to the rolling texture. The anisotropy reduced as rolling temperature increasing from 573K to 673K and this may be attributed to the completion of DRX.

Abstract: Addition of RE elements to Al-containing Mg alloys can improve properties of Mg alloys at elevated temperatures. In the present investigation, hot-extruded AZ31+x%Nd. (x=0.1,0.3,0.6and1.0 wt%) wrought Mg alloy were prepared .The effects of Nd on microstructures and mechanical properties at room temperature of new alloy were investigated. The investigation found that Nd can bring about two kind of precipitation phases . One is AlNd phase, the other is AlNdMn phase, which were identified as Al11Nd3 and Al8NdMn4 by X-ray diffraction and TEM.

Abstract: The cold-compressed AZ31 magnesium alloys with different (2.5%, 5%, 7.5%, 10%, 12.5% and 15%) were annealed at different temperatures (573, 623 and 673K) for different time. With aid of the optical microscopy, and microhardness tester, the microstructural evolution during annealing at different temperature of the compressed AZ31 has been investigated. The microstructural characterized results were further related to the hardness test results and the calculated activation energy. The results showed that for the compressed AZ31, the recrystallization can occur on the samples with the strain just above 10% and the deformation twinning plays an important role on the nucleation and grain growth of the recrystallization. It was found that the twinning boundary was the location of the recrystallization nuclei and a lot of recrystallized grains with equiaxed shape were found along the twinning boundaries. The relationships among the nuclei orientations and the crystallographic orientations on both sides of the twining boundary have been statistically investigated. The effects of the compressed strain and the annealing temperature on annealing behavior were also discussed based on the experimental results.

Abstract: The hexagonal crystal structure of AZ31 results in a very high mechanical anisotropy and a poor formability of this alloy. In order to address these problems the influence of twinning, slip and dynamic recrystallization (DRX) on the microstructure and texture evolution during compression of AZ31 has been studied over a range of temperatures. Cylindrical samples were tested uniaxially in compression from room temperature to 350oC, with the compression axis parallel to either the normal direction (ND) or the transverse direction (TD) of the hot-rolled sheet from which the samples were cut. The microstructure was characterized using electron backscattered diffraction (EBSD) analysis. Extensive twinning was only observed in the TD samples at all temperatures. The effect of the difference in twinning and slip between the TD and ND samples on the mechanism of dynamic recrystallization has also been investigated. For this, the grains formed during DRX were identified by their appearance in EBSD orientation maps and the orientations of these grains determined.

Abstract: Rolling and punching techniques of AZ31 alloy were investigated in this paper. Various rolling experiments were carried out to make fine-grained Mg sheets. Punching tests were conducted at the temperatures range from 70 to 300 oC. The analysis revealed that there existed an excellent warm forming temperature for as-rolled AZ31 alloy. A warm deep punching tool setup using heating elements was designed and manufactured to produce the cell phone. Microstructures were observed using optical and scanning electron microscope equipped with EBSD. The textures in as-rolled and as-annealed specimens attribute to different mechanical properties along the various direction.

Abstract: In this study, AZ31 in form of sheet, plate and extruded rod and AZ61 wire with different initial grain sizes were used to investigate the effect of initial grain size on recrystallization behavior and the formation of fine recrystallized grain (the so-called necklace) structure. Nucleation and growth of recrystallized grains along grain boundaries has been examined. In order to observe the effect of initial grain size and deformation on static recrsytallization and necklace formation, the specimens were annealed at 100-250°C for 10min--2hr. Specimens are also stretched to a total strain of 10, 20 and 40% at 300°C at an initial cross head speed of 1x10-3 s-1 for dynamic recrystallization studies. The results suggest that there exists a grain size limit, below which a necklace structure is not observed.

Abstract: The influence of Al-10.5%Sr master alloy, which is much cheaper than Mg-Sr master alloys, on the as-cast microstructure of the AZ31 alloy was investigated. The research results revealed that the Al-10.5%Sr master alloy produced obvious modification of the as-cast microstructure of the AZ31 alloy, and the modification efficiency increased with the holding time from 0min to 60min and the amount of Sr from 0.01% to 0.1%. Moreover, the results also showed that the Al-10.5%Sr master alloys of different states had different modification efficiency on the as-cast microstructure of the AZ31 alloy. The Al-10.5%Sr master alloys in extrusion deformation state and rapid solidification state had better modification efficiency than the Al-10.5%Sr master alloys received and in heat treatment state, which could be related to the microstructure of the Al-10.5%Sr master alloys with different states.

Abstract: Due to the deformation mechanisms and the typical basal texture rolled magnesium sheets show a significant asymmetry of flow stress in tension and compression. In order to avoid this undesired behavior it is necessary to achieve non-basal texture during rolling, or at least, to reduce the intensity of the basal texture component. The reduction of the anisotropy caused by the basal texture is very important for subsequent forming processes. This project aims at optimizing the hot rolling process with special consideration of texture effects. The development of the model is carried out in close cooperation with the experimental work on magnesium alloy AZ31 .The experimental results are required for the determination of model parameters and for the verification of the model. Deformation-induced texture is described by the visco-plastic self-consistent (VPSC) model of Lebensohn and Tomé. The combination of deformation and recrystallization texture models is applied to hot compression tests on AZ31, and it is found, that the model describes the observed texture and hardening/softening behavior well. In some cases rotation recrystallization occurs in AZ31 which appears to be a possibility to reduce the undesired basal rolling texture.