MICROSTRUCTURE AND MECHANICAL PROPERTIES OF HOT EXTRUDED Mg- 3Zn-1Cu-0.7Mn ALLOY PRODUCED BY POWDER METALLURGY (original) (raw)
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Microstructure and Mechanical Properties of an Extruded Mg-2Dy-0.5Zn Alloy
Microstructure and mechanical properties of an extruded Mg-2Dy-0.5Zn (at.%) alloy during isothermal ageing at 180 • C were investigated. Microstructure of the as-extruded alloy is mainly composed of α-Mg phase, 14H long period stacking order (LPSO) phase and small amounts of (Mg, Zn) x Dy particle phases. During ageing, the 14H LPSO phase forms and develops and its volume fraction increases with increasing ageing time. Tensile test showed that the peak-aged alloy exhibits similar yield and ultimate tensile strengths and elongation to failure at room temperature, 100 • C and 200 • C, but excellent elevated temperature strengths at 300 • C as compared to the as-extruded and over-aged alloys. The analysis showed that the excellent elevated temperature strengths of the peak-aged alloy are attributed to the LPSO phase strengthening and the grain refinement strengthening, and the role of the LPSO strengthening is related to not only its amount, but also its morphology.
Materials Chemistry and Physics, 2018
The microstructure, texture and mechanical properties of Mg-6wt%Zn-0.5wt%Zr (ZK60) alloys with different La contents (0, 0.5 and 1 wt%) were investigated. The alloys were produced by lowpressure die casting and extruded at 300 °C and 400 °C, following homogenization at 400 °C for 24 h. La addition to ZK60 alloy resulted in a formation of Mg-Zn-La ternary phase, generating a semicontinuous network structure in their as-cast state. After extrusion, secondary phases were broken into fine particles distributed along the extrusion direction. These fragmented particles led to a nucleation of new grains around them i.e. particle stimulated nucleation (PSN), and promoted dynamic recrystallization (DRX) during extrusion. Therefore, increasing La content led to an increase in DRX fraction. Higher extrusion temperature resulted in larger DRXed grains and higher DRX fraction. The basal texture intensity was also decreased with increasing La addition and extrusion temperature by PSN mechanism and solute atoms of La. The ZK60-1La alloy extruded at 300 °C showed a superior yield strength of 311 MPa and ultimate tensile strength of 360 MPa as a result of significant grain refinement and dispersion strengthening. Increasing extrusion temperature resulted in a decrease in yield and ultimate tensile strengths and increase in ductility.
Characterization of the High-Strength Mg–3Nd–0.5Zn Alloy Prepared by Thermomechanical Processing
Acta Metallurgica Sinica (English Letters), 2018
Magnesium alloys based on Nd and Zn are promising materials for both aviation industry and medical applications. Superior mechanical properties of these materials can be achieved by thermomechanical processing such as extrusion or rolling and by aging treatment, which can significantly strengthen the alloy. The question remains especially about the connection of texture strength created in the alloys based on the specific conditions of preparation. This work focuses on the Mg-3Nd-0.5Zn magnesium alloy prepared by hot extrusion of the as-cast state at two different temperatures combined with heat pre-treatment. Extrusion ratio of 16 and rate of 0.2 mm/s at 350 and 400°C were selected for material preparation. The structures of prepared materials were studied by scanning electron microscopy and transmission electron microscopy. The effect of microstructure on mechanical properties was evaluated. Obtained results revealed the strong effect of thermal pre-treatment on final microstructure and mechanical properties of extruded materials. The Hall-Petch relation between grain size and tensile yield strength has been suggested in this paper based on the literature review and presented data. The observed behavior strongly supports the fact that the Hall-Petch of extruded Mg-3Nd-0.5Zn alloys with different texture intensities cannot be clearly estimated and predicted. In addition, Hall-Petch relations presented in literature can be sufficiently obtained only for fraction of the Mg-3Nd-0.5Zn alloys.
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2009
The effect of Ca element on the hot workability and microstructure evolution of AZ31 magnesium alloy was investigated. Conventional AZ31, AZ31 + 0.7 wt.%Ca, and AZ31 + 2.0 wt.%Ca alloys were tested. Electron back scattered diffraction microscopy revealed that the alloys containing Ca exhibited much finer and more homogeneous microstructure than the conventional AZ31 alloy. Hot compression and tensile tests showed that the Ca element generally increased flow strength and decreased ductility at low temperature. High temperature elongation was considerably improved by the operation of the thermally activated process. TEM work suggested that the large volume fraction of fine (Mg, Al) 2 Ca particles played an important role in preventing significant grain growth of the AZ31 + 2.0Ca alloy.
Transstellar Journals, 2019
A composite based on Mg-3Zn-1Cu-0.7Mn alloy reinforced withAl 2 O 3 was synthesized using blend-press-sinter powder metallurgy route and hot extruded at 400 o C. The study concentrates on investigating the effectiveness of alumina as reinforcement and analyzing the effect of stress relieving on the mechanical and microstructural properties of the composite. The results of the study indicate that the ultimate tensile strength, yield strength and fracture strain of the composite was increased in the composite compared to the pure Mg metal. It is also proved that stress relieving has a significant role on the ultimate tensile strength and fracture strain in the composite.
Improving the mechanical properties of extruded Mg–3Al–1Zn alloy by cold pre-forging
Scripta Materialia, 2013
This study demonstrates that cold pre-forging (CPF) conducted before extrusion is a promising means for improving the mechanical properties of extruded magnesium alloys. The CPF process induces numerous twins in the billet, which in turn provides nucleation sites for dynamic recrystallization during extrusion, leading to an increase in the dynamically recrystallized (DRXed) fraction of the extruded alloy. This process increases the uniformity of the DRXed grain structure, thereby improving the strength and ductility of the extruded alloy.
Journal of Alloys and Compounds, 2015
The effect of aging prior to extrusion (APE) on the microstructure and mechanical properties of Mg-7 Sn-1Al-1Zn (wt.%) alloy was investigated under various extrusion conditions. The extruded alloy exhibited a partially or fully recrystallized (DRXed) structure with fine Mg 2 Sn precipitates, with the fraction and size of the DRXed grains decreasing with a reduction in extrusion temperature and ram speed. The numerous precipitates formed by APE also reduces the size of the DRXed grains and increases the overall amount of precipitate in the extruded alloy, thereby improving the yield and tensile strength regardless of the extrusion conditions. The ductility of the alloy was also improved by APE when extruded at relatively high temperature and speed, which is attributed to the suppressed formation of coarse banded Mg 2 Sn; however, a deterioration in ductility was observed at low ram speed and/or low extrusion temperature due to the reduction in the fraction of DRXed grains and increased amount of Mg 2 Sn precipitates. Furthermore, the extruded alloy with APE showed superior strength and ductility to that aged after extrusion, indicating that APE is the more effective means of improving the mechanical properties of extruded alloy.
Hot Extrusion Effect on the Microstructure and Mechanical Properties of a Mg–Y–Nd–Zr Alloy
Strength of Materials, 2018
Nd alloy was prepared by casting and hot extrusion. The microstructure and mechanical properties of OM, SEM, XRD, TEM, and tensile tests were investigated with casting and hot extruded alloys. The results demonstrate that in a casting Mg-Y-Nd-Zr alloy, the a-Mg matrix is separated into the cell structure by a discontinuously distributed coarse Mg 24 Y 5 /a-Mg eutectic structure and fine Mg 12 Nd particles. TEM analysis shows that the Mg 12 Nd and Mg 24 Y 5 phases have the orientation of [ ] //[ ] 001 0221
Effect of Ca and Zn additions on the mechanical properties of Mg produced by powder metallurgy
AIP Conference Proceedings, 2017
Magnesium and its alloys are among important research topics in view of their excellent biocompatibility.In this study mechanical and microstructure properties of hot sintered Mg-Zn-Ca alloys were studied.The effects of the addition of different amounts Ca and Zn were added to the base material has been processed by powder metallurgy method.resulting microstructures densities and compression test behaviors of the Mg-based alloys were studied.Visual inspection using SEM (Scanning Electron Microscope) analyses indicates that the microstructure of the composite is also greatly effected by these parameters. In addition, EDS (Energy Dispersive X-Ray Spectroscopy) analyses were performed for reliable determination of the chemical composition.