Properties Of As-cast Mg Research Articles

Effect of Nd on Microstructure and High-Temperature Mechanical Properties of As-cast Mg–Y–Nd–Zn–Zr Alloy

Effect of Nd on Microstructure and High-Temperature Mechanical Properties of As-cast Mg–Y–Nd–Zn–Zr Alloy

Microstructure and damping properties of Mg–Si binary hypoeutectic alloys

The effects of Si content and solution heat treatment on the microstructure and damping properties of as-cast Mg–Si hypoeutectic alloys were investigated. Si has the capacity to refine grains of pure magnesium. The three contents of Mg–Si hypoeutectic alloys are all high-damping alloys. The damping value of the as-cast Mg–0.5 wt-%Si alloy was higher than that of the Mg–0.3 wt-%Si and Mg–0.8 wt-%Si alloys in the small strain amplitude area. Compared to the as-cast state, the solution heat-treated Mg–Si hypoeutectic alloys show an increase in damping values, which are close to each other for the three contents in the small strain amplitude area, and decrease with increasing Si content in the high strain amplitude area as in the as-cast state.

Enhancing the mechanical properties of Mg–Al alloy by introducing Al2Y nanoparticles via rapid-cooling solidification and optimized heat treatments

Coarse grain and poor thermal stability of Mg17Al12 are usually present in the as-cast Mg–Al alloys, which are detrimental to the mechanical properties. In this work, the microstructure evolution, and mechanical properties of as-cast AZ31-1Y alloy with different cooling rates (4.0–29.9 °C/s) were systematically investigated by thermal analysis and microstructure characterization. The results show that the addition of Y to AZ31 alloy results in the formation of primary Al2Y and eutectic Al2Y, while suppressing the formation of β-Mg17Al12. The AZ31-1Y alloy with a cooling rate of 29.9 °C/s exhibits the finest grain, with a grain refinement efficiency 40.9 % higher than that of AZ31 alloy with a cooling rate of 4.0 °C/s. After heat treatment, the acicular eutectic Al2Y is modified into a granular shape and numerous nano-sized Al2Y precipitates are observed within the α-Mg matrix. The addition of Y can effectively improve the mechanical properties of AZ31 alloy under high cooling rates, but the mechanical properties deteriorate at slower cooling rates due to stress concentration caused by the agglomeration of large-sized Al2Y particles. The optimal mechanical properties of the AZ31-1Y alloy are achieved at a cooling rate of 29.9 °C/s combined with subsequent heat treatment, and its YS, UTS, and EL reached up to 69 MPa, 293 MPa, and 14.5 %, respectively. Moreover, the related strengthening mechanisms are quantified. It is believed that this work can provide guidance for controlling the microstructure and optimizing the mechanical properties of as-cast Mg–Al alloys.

Enhanced corrosion resistance of the as-cast AZ91 magnesium alloy by micro-addition of the strontium and rare earth elements

The synergetic effect of strontium (Sr) and rare earth elements (RE) on the corrosion properties of as-cast Mg–9Al–1Zn alloy were studied. Via the addition of 0.5 wt-% RE and 0.5 wt-% Sr (RE/Sr ratio of 1), a remarkable reduction in the corrosion rate of AZ91 was observed. The reason was found to be related to the decrement of the micro-galvanic corrosion by the modification of the β-Mg17Al12 phase (changing its morphology from semi-continuous to a more spheroid shape) and formation of proper amounts of Al11RE3 and Al4Sr intermetallics. However, the excess RE/Sr ratio impaired the corrosion resistance, which can be related to the micro-galvanic effect by excess amounts of Al11RE3 and Al4Sr intermetallics.

Effects of trace Ca addition on microstructure and mechanical properties of as-cast Mg-Sm-Gd-based alloy

The effects of trace amounts of Ca on the microstructure and mechanical properties of as-cast Mg−Sm− Gd−Zn−Zr alloy were systematically investigated mainly by means of transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and tensile test. The results reveal that the dominant intermetallic compound in Mg−Sm−Gd−Zn−Zr alloy is Mg3RE phase with significant enrichment of Zn. The addition of Ca in Mg−Sm−Gd−Zn−Zr alloy can not only refine grains, but also promote the formation of Mg5RE phase and solute-enriched stacking faults (SESFs). The coherent interface indicates that Mg3RE phase can act as the nucleation site of Mg5RE phase. Finally, the decreased grain size and the formation of Mg5RE phase and SESFs in the Ca-modified alloy are beneficial to the enhancement of mechanical properties.

Effect of Sm content on microstructure evolution and mechanical properties of as-cast Mg−6Al−2Sr alloys

Effect of Sm content on microstructure evolution and mechanical properties of as-cast Mg−6Al−2Sr alloys

Effects of heat treatment and Y addition on the microstructure and mechanical properties of as-cast Mg–Si alloys

In Mg–Si alloys, both primary and eutectic Mg2Si particles normally appear with sharp edges, which can lead to weak mechanical properties as the result of stress concentration at the sharp corners of these brittle particles. Thus, it would be of great importance to modify the morphology of these particles. In this study, microstructure modification mechanisms after 0.5 wt% Y addition and heat treatment (HT) at 420 °C for 24 h are comprehensively studied in hypo-eutectic Mg–1Si and hyper-eutectic Mg–2Si alloys. Microstructural observations were performed using optical and scanning electron microscopy equipped with electron disperse spectroscopy, while phase analysis was done by X-ray diffraction. Mechanical properties of the studied alloys were evaluated by shear punch testing technique. The obtained results indicate that 0.5% Y addition to the as-cast Mg–1Si and Mg–2Si alloys could modify morphology of the eutectic Mg2Si from coarse lamellar to very short rod-shaped. The poisoning effect of Y was the main mechanism for this modification. The ultimate shear strength (USS) increased after Y addition to the Mg–1Si and Mg–2Si alloys, due to the modified eutectic Mg2Si morphology and also formation of fine Y-containing particles. Moreover, it was observed that HT could modify the morphology of the eutectic Mg2Si phase to the punctiform or disconnected rod-shaped in the studied alloys. Another important effect of HT was observed to be rounding sharp corners of the primary Mg2Si particles and changing their morphology to some new shapes such as star-like, indicating unstable morphology of the primary Mg2Si particles in the Mg–2Si–0.5Y alloy at high temperature. The USS values were improved for the Mg–1Si and Mg–2Si alloys after HT due to the modified morphology of the Mg2Si particles.

Effect of Al addition on the grain refinement and mechanical properties of as-cast Mg–5Y–4Sm alloys

Effect of Al addition on the grain refinement and mechanical properties of as-cast Mg–5Y–4Sm alloys

Improving room-temperature ductility of a Mg–Zn–Ca alloy through friction stir processing

The effect of friction stir processing (FSP) on the microstructure evolution and mechanical properties of as-cast Mg–Zn–Ca (Mg-1.2wt%Zn-0.1wt%Ca) alloy was investigated. The result shows that the average grain size of the stir zone is greatly refined from ∼170 μm to ∼13 μm. Moreover, a basal texture is formed in the stir zone, and the c-axis of the grain is tilted to the normal direction about 42.6° away from the processing direction. Although the tensile strength has little improvement compared to the as-cast alloy, the elongation is increased from 24.6% to 45.4%. The excellent room-temperature ductility of the FSP alloy is mainly attributed to the fine grain size and the preferential orientation of the grains in the stir zone. The Schmid factor up to 0.44 means that basal slip is beneficial to be activated, resulting in a high elongation.

Effect of Bi and Zn Additions on the Microstructures and Mechanical Properties of As-Cast Mg–7Sn–2Al-Based Alloys

Effect of Bi and Zn Additions on the Microstructures and Mechanical Properties of As-Cast Mg–7Sn–2Al-Based Alloys

Correction to: Effects of I- and W-Phases Under Identical Conditions on Microstructure and Mechanical Properties of As-Cast Mg–Zn–Y Alloys at Room and Elevated Temperatures

Correction to: Effects of I- and W-Phases Under Identical Conditions on Microstructure and Mechanical Properties of As-Cast Mg–Zn–Y Alloys at Room and Elevated Temperatures

Effect of Y on microstructure evolution and mechanical properties of Mg−4Li−3Al alloys

To obtain magnesium alloys with a low density and improved mechanical properties, Y element was added into Mg−4Li−3Al (wt.%) alloys, and the effect of Y content on microstructure evolution and mechanical properties was investigated by using optical microscopy, scanning electron microscopy and tensile tests. The results show that mechanical properties of as-cast Mg−4Li−3Al alloys with Y addition are significantly improved as a result of hot extrusion. The best comprehensive mechanical properties are obtained in hot-extruded Mg−4Li−3Al−1.5Y alloy, which possesses high ultimate tensile strength (UTS=248 MPa) and elongation (δ=27%). The improvement of mechanical properties of hot-extruded Mg−4Li−3Al−1.5Y alloy was mainly attributed to combined effects of grain refinement, solid solution strengthening and precipitation strengthening.

Microstructure and mechanical properties of as-cast Mg–Nd–Zn–Y–Zr alloys

Mg-2.4Nd-0.2Zn-0.5Zr-xY (x=0, 0.6, 1.2, 1.8wt.%) alloys were fabricated by a casting method, the microstructure and mechanical properties of as-cast alloys were investigated. The results demonstrate that the A, B, C and D alloys are composed mainly of α-Mg and Mg12Nd phases. Phases containing Y were not formed, because trace amounts of Y element was completely dissolved into Mg matrix. The addition of Y was found to improve the mechanical properties of the alloys. The Mg-2.4Nd-0.2Zn-0.4Zr-1.8Y alloy exhibits the optimal mechanical properties in the as-cast condition, the maximum value of ultimate tensile strength, yield strength and elongation to failure were 192MPa, 168MPa and6.5%, respectively.

Synergistic effects of alloying, homogenization, and hot extrusion on the mechanical properties of as-cast Mg–Al–Ca magnesium alloys

Synergistic effects of alloying, homogenization, and hot extrusion on the mechanical properties of as-cast Mg–Al–Ca magnesium alloys

Effects of I- and W-Phases Under Identical Conditions on Microstructure and Mechanical Properties of As-Cast Mg–Zn–Y Alloys at Room and Elevated Temperatures

Three alloys (Mg–6Zn–1.2Y, Alloy I; Mg–3.65Zn–1.65Y, Alloy II; and Mg–4.3Zn–1.4Y, Alloy III) with same volume fraction and grain size were designed to evaluate the effects of the I-phase (Mg3Zn6Y) and W-phase (Mg3Zn3Y2), which are the major phases in Mg–Zn–Y alloys, on the mechanical properties. The tensile strength of Alloy I with the I-phase at room temperature was the highest among the tested alloys because the coherent interface between the I-phase and the α-Mg phase was more resistant to cracking than the incoherent interface between the W-phase and the α-Mg phase. A cross-sectional microstructure analysis of a sample that was tensile-tested at 423 K revealed that the morphology of the I-phase remained relatively stable. In contrast, the W-phase was broken and fragmented during the tensile test at 423 K because it had higher brittleness under the test conditions. Therefore, the tensile and creep properties of Alloy I at 423 K were better than those of Alloys II and III containing the W-phase. According to the results, the I-phase in the Mg-Zn-Y alloy was more beneficial to the mechanical properties at room temperature and 423 K than the W-phase.

Enhanced mechanical properties of as-cast AZ91 magnesium alloy by combined RE-Sr addition and hot extrusion

The synergetic effects of strontium (Sr) and rare earth elements (RE) on the modification of the microstructure and enhancement of the mechanical properties of as-cast Mg–9Al–1Zn alloy were studied. Based on the microstructural analysis, phase identification, and tensile tests, it was revealed that the combined RE and Sr addition results in superior mechanical properties compared to those of solo additions of RE or Sr. This was related to both morphological enhancement of the β-Mg17Al12 intermetallics notably by RE towards the disappearance of the intergranular network and modification of the Al11RE3 particles by Sr. The enhancement of tensile properties was achieved by increasing the RE/Sr ratio in the Sr-RE containing alloys and the best combination of mechanical properties was observed for the Mg–9Al–1Zn-0.9RE-0.1Sr alloy. Owing to the dissolution of the β phase and solid solution strengthening effect of Al, the tensile properties of the Mg–9Al–1Zn-0.9RE-0.1Sr alloy were enhanced by homogenization treatment. Moreover, the hot extrusion process remarkably augmented the tensile properties by combined effects of grain refinement and fracturing and distributing the intermetallic particles.

The creep behavior of Mg–9Al–1Si–1SiC composite at elevated temperature

Abstract The creep properties of as-cast Mg–9Al–1Si alloy and Mg–9Al–1Si–1SiC composite were compared. The results show that Mg–9Al–1Si–1SiC composite performs a better creep resistance than that of Mg–9Al–1Si alloy at constant temperature and stress (473 K,70 MPa). Besides, the creep behavior of Mg–9Al–1Si–1SiC composite at various temperature from 448 K to 498 K and under stresses of 70–90 MPa were systematically investigated. The Mg–9Al–1Si–1SiC composite exhibited a stress exponent from 5.5 to 6.9 and the creep activation energy fell within the range of 86–111 kJ/mol. The results showed that the creep mechanism of Mg–9Al–1Si–1SiC composite was mainly attributed to the effects of secondary phase strengthening mechanism and dislocation climb mechanism.

Crystal structure, phase content, and tensile properties of As-cast Mg–Gd–Y–Al alloys

The lattice parameters, phase content, and tensile properties of as-cast Mg–xGd–(4–x)Y–2Al (x = 0, 2, 4) alloys were investigated via X-ray diffraction, Rietveld refinement, scanning electron microscopy, and transmission electron microscopy. The Mg-RE phase, Al2RE phase, and Al11RE3 phase occurred in all three alloys. Furthermore, the cell volume and axial ratio (c/a) of the α-Mg matrix decreased with increasing (0–4 wt.%) Gd content. The abundance of the Al2RE and Mg-RE phases decreased with increasing Gd content, whereas that of the Al11RE3 phase increased. Moreover, Al2RE particles formed at the grain centers served as active nucleation sites, thereby leading to grain refinement, and acicular Al11RE3 phases restricted the growth of α-Mg. The tensile properties improved with increasing Gd content. In fact, the optimal mechanical properties (yield strength: 77.83 MPa, ultimate tensile strength: 195.01 MPa, and elongation: 15.71 %) were obtained for the Mg–4Gd–2Al alloy. Furthermore, strengthening of the material occurred mainly via second-phase strengthening and solid-solution strengthening. Block Al2RE particles can cut the matrix during the stretching process, and the acicular Al11RE3 phase may play a major role in enhancing the tensile properties. In addition, the ductility of the alloy system improved with decreasing axial ratio (c/a).

The quasicrystal of Mg–Zn–Y on discharge and electrochemical behaviors as the anode for Mg-air battery

In this work, the effect of quasicrystal I phase (Mg3Zn6Y) on electrochemical behaviors and discharge properties of as-cast Mg–Zn–Y alloys with different Zn/Y ratio for Mg-air batteries are systematically investigated in 3.5 wt % NaCl electrolyte. The Mg–6%Zn–1%Y (wt.%) alloy is composed of Mg matrix and I phase, while the Mg7Zn3 phase appears in Mg–10%Zn–1%Y alloy. The Mg–Zn–Y anodes have higher open circuit potential, electrochemical activity and corrosion resistance than the contrasted ZK60 anode. They also have higher cell voltage, specific capacity and anodic efficiency with more stable discharge curves. The I phase is responsible for such improvements. The Mg–6%Zn–1%Y alloy achieves its best discharge capacity and anodic efficiency at the 40 mA cm−2, with the values of 1162.79 mAh·g−1 and 55.14%, respectively, which are 22.38% and 23.14% higher than ZK60 anode. Shallow pits with smooth surfaces are observed in Mg–Zn–Y anodes after discharge process. Some small holes associated with the desorption ability are detected as well.

Unraveling the effects of Zn addition and hot extrusion process on the microstructure and mechanical properties of as-cast Mg–2Al magnesium alloy

The effects of zinc addition and hot working via extrusion process on the microstructure and mechanical properties of as-cast Mg–2Al-xZn (x = 0, 0.5, 1, 2, and 5 wt%) magnesium alloys were studied. It was revealed that the simultaneous addition of 2 wt% Al and 0.5 wt% Zn (known as AZ20 alloy) is an effective way for refining of α-Mg in the as-cast condition, which resulted in a significant enhancement of tensile properties and changing the fracture mechanism from brittle cleavage facets to fibrous appearance characterized by ductile dimples. Further addition of Zn had negligible effect on the grain size but resulted in the appearance of Mg21(Zn,Al)17 intermetallic known as φ-phase, where the latter resulted in the deterioration of tensile properties of as-cast ingot due to its unfavorable morphology. After extrusion process, fine and recrystallized microstructures were observed along with the fractured and dispersed second phase particles. Besides the effect of fine grain size as verified by the Hall-Petch relationship, the presence of finely dispersed particles in the ZA52 (Mg–5Zn–2Al) alloy was found to be favorable in improving the mechanical properties and tensile toughness of the extruded alloy. Based on these findings, it was recommended to use these alloys in the wrought condition.