Effects of Cu addition on microstructure and mechanical properties of as-cast magnesium alloy ZK60

doi:10.1016/S1003-6326(14)63101-0

Transactions of Nonferrous Metals Society of China

Volume 24, Issue 3, March 2014, Pages 605-610

https://doi.org/10.1016/S1003-6326(14)63101-0 Get rights and content

Abstract

The effects of Cu addition on the microstructure and mechanical properties of the as-cast magnesium alloy ZK60 were investigated with optical microscope, SEM, TEM, XRD, EPMA and tensile tester. The mechanism by which the mechanical properties are affected by Cu addition was discussed. The results show that Cu can effectively eliminate the intragranular solute segregations in the alloy, and the grain size of the alloy is decreased considerably with increasing the Cu amount. A ternary eutectic phase MgZnCu with a face-centered cubic structure is identified in the Cu-bearing alloys, which predominantly distributes at the grain boundary and acts as the nucleation sites of microcracks during the plastic deformation process. It is also found that the tensile properties of the alloy firstly increase by the trace addition of 0.5%–1% Cu and then decrease by a further addition up to 2.0%.

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Microstructures, mechanical properties and degradability of Mg-2Gd-0.5(Cu/Ni) alloys: A comparison study
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Citation Excerpt :
The average grain sizes of Mg-2Gd-0.5Cu alloy, Mg-2Gd-0.25Cu-0.25Ni alloy, and Mg-2Gd-0.5Ni alloy were 10.9, 6.7, and 5.1 μm, respectively, indicating different grain refinement effects of Ni and Cu. It is generally believed that the segregation of alloying elements at the front of the solid-liquid interface was conducive to grain refinement during solidification, and the refinement efficiency of different elements can be estimated by the grain refinement factor (GRF) [33–35]. The element with higher GRF usually shows a stronger ability to refine grain sizes, and the GRF of Ni and Cu is 6.13 and 5.18, respectively [36,37].
Low alloying Mg-2Gd-0.5(Cu/Ni) alloys for sealing tools in the oil and gas industry were prepared. The differences in the effects of minor Cu and Ni additions on microstructures and properties of the Mg-2Gd alloy were compared. The results showed that adding Ni was more effective than adding Cu in refining grain sizes, strengthening the basal fiber texture, and promoting the formation of LPSO phases, resulting in higher strength. The tensile yield strength/elongation of the Mg-2Gd-0.5Cu alloy, Mg-2Gd-0.25Cu-0.25Ni alloy, and Mg-2Gd-0.5Ni alloy was 146 MPa/23.7%, 175 MPa/23.1%, and 248 MPa/18.2%, respectively. The decreased elongation was attributed to the basal fiber texture and the presence of coarse LPSO phases. In terms of the corrosion rate in 3.5 wt.% NaCl solution, it rose from 112 mm y^–1 for the Mg-2Gd-0.5Cu alloy to 269 mm y^–1 for the Mg-2Gd-0.25Cu-0.25Ni alloy and 490 mm y^–1 for the Mg-2Gd-0.5Ni alloy, indicating that the addition of Ni instead of Cu showed a more significant promoting effect on the degradability of Mg alloys, which was related to more refined grains, the stronger basal fiber texture, and a larger amount of LPSO phases.
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Cu can elevate the eutectic temperature, leading to an increase in the solution treatment temperature. Cu also has a significant influence on the ageing behavior of Mg-Zn alloy [11–14], increasing the number density and homogeneity of the strengthening precipitates [9]. Rare earth elements, such as La, Ce, Nd, Gd and Y, are also common components of Mg alloys.
The strengthening mechanism and stress corrosion cracking (SCC) behavior of a new Mg-6Zn-1Y-0.5Cu-0.5Zr alloy (given the name “ZWCK6100″) were investigated in this work. The results showed that the microstructure, mechanical properties and stress corrosion resistance were significantly affected by the combined addition of Cu and Y. The alloy consisted of α-Mg, Zn₂Zr, CuMgZn, rod-shaped MgZn₂ precipitates and I phase (Mg₃Zn₆Y), and displayed a balance between strength and ductility, with the yield strength, ultimate tensile strength and elongation being 320.3 MPa, 351.5 MPa and 19.8%, respectively. The main strengthening mechanisms were found to be grain refinement, second phases and texture. In addition, the stress corrosion resistance was assessed by slow strain rate testing and fractography. These tests showed that ZWCK6100 alloy exhibited improved SCC resistance and low SCC sensitivity in 3.5 wt% NaCl solution. The novel ZWCK6100 alloy may serve as a promising magnesium alloy for industrial applications.
Improvement of mechanical properties of in situ Mg-Si composites via Cu addition and hot working
2022, Journal of Alloys and Compounds
Citation Excerpt :
Interestingly, copper can also be added to other metallic alloys for the enhancement of mechanical/functional properties [33]. Copper addition to Mg alloys has been recently practiced for the enhancement of mechanical properties (for Mg-Zn alloys [34,35], Mg-Zn-Al alloys [36], Mg-SiC composites [37], Mg-Y alloy [38], and Mg-Al alloys [39]), damping applications [40–42], and biomedical applications [43–45]. Regarding the tensile properties, it has been shown in several studies that there is an optimum amount of Cu (below 1 wt%) for obtaining the expected enhancements [34,35].
The synergistic effects of copper addition and hot extrusion process on the modification of microstructure and enhancement of mechanical properties of a common in situ hypereutectic Mg-Si metal-matrix composite were studied. It was revealed that Cu addition at the microalloying level of 0.5 wt% was very effective in modifying the primary and eutectic Mg₂Si phases, which led to the enhancement of the as-cast mechanical properties. Further Cu additions (2, 4.5, 8, and 15 wt%) led to the appearance of the α-Mg/Mg₂Cu eutectic constituent and distinct α-Mg regions with the disappearance of Mg₂Si eutectics in the ingots, which was ascribed to the change in the solidification path. Contrary to the favorable effect of Cu at the micro-addition level, higher additions led to poor tensile properties due to the deleterious effect of eutectics. Fragmentation and dispersion of intermetallics, as well as intense grain refinement by dynamic recrystallization (DRX) were observed for the extruded composites due to the hot deformation effects, which resulted in the enhancement of the ultimate tensile strength, total elongation, and tensile toughness. Accordingly, it was concluded that Cu addition to Mg-Si composites should be limited to small amounts for modification effects, and if it is combined with the elevated-temperature thermomechanical processing, the optimum strength-ductility trade-off can be achieved.

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: Foundation item: Project (51201088) supported by the National Natural Science Foundation of China; Project (12C0324) supported by the Research Foundation of Education Bureau of Hunan Province, China; Project (2011XQD26) supported by Doctoral Scientific Research Foundation of University of South, China; Project ([2011] 76) supported by the Construct Program of the Key Discipline in Hunan Province, China

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Effects of Cu addition on microstructure and mechanical properties of as-cast magnesium alloy ZK60

Abstract

Journal of University of Science and Technology Beijing

Transactions of Nonferrous Metals Society of China

Materials and Design

Materials Science and Engineering A

Transactions of Nonferrous Metals Society of China

Journal of Alloys and Compounds

Materials Science and Engineering A

Transactions of Nonferrous Metals Society of China