Bei Tang, Jinlong Fu, Jingkai Feng, Xiting Zhong, Yangyang Guo, and Haili Wang, Effect of Zn content on microstructure, mechanical properties and thermal conductivity of extruded Mg–Zn–Ca–Mn alloys, Int. J. Miner. Metall. Mater., 30(2023), No. 12, pp.2411-2420. https://doi.org/10.1007/s12613-023-2676-8
Cite this article as:
Bei Tang, Jinlong Fu, Jingkai Feng, Xiting Zhong, Yangyang Guo, and Haili Wang, Effect of Zn content on microstructure, mechanical properties and thermal conductivity of extruded Mg–Zn–Ca–Mn alloys, Int. J. Miner. Metall. Mater., 30(2023), No. 12, pp.2411-2420. https://doi.org/10.1007/s12613-023-2676-8
Bei Tang, Jinlong Fu, Jingkai Feng, Xiting Zhong, Yangyang Guo, and Haili Wang, Effect of Zn content on microstructure, mechanical properties and thermal conductivity of extruded Mg–Zn–Ca–Mn alloys, Int. J. Miner. Metall. Mater., 30(2023), No. 12, pp.2411-2420. https://doi.org/10.1007/s12613-023-2676-8
Cite this article as:
Bei Tang, Jinlong Fu, Jingkai Feng, Xiting Zhong, Yangyang Guo, and Haili Wang, Effect of Zn content on microstructure, mechanical properties and thermal conductivity of extruded Mg–Zn–Ca–Mn alloys, Int. J. Miner. Metall. Mater., 30(2023), No. 12, pp.2411-2420. https://doi.org/10.1007/s12613-023-2676-8
Mg–Zn–Ca–Mn series alloys are developed as promising candidates of 5G communication devices with excellent thermal conductivities, great ductility, and acceptable strength. In present paper, Mg–xZn–0.4Ca–0.2Mn (x = 2wt%, 4wt%, 6wt%) alloys were prepared by a near-solidus extrusion and the effect of Zn content on mechanical and thermal properties were investigated. The results showed that the addition of minor Ca led to the formation of Ca2Mg6Zn3 eutectic phase at grain boundaries. A type of bimodal microstructure occurred in the as-extruded alloys, where elongated coarse deformed grains were embedded in refined recrystallized grains matrix. Correspondingly, both yield strength and ductility of the alloys were significantly enhanced after extrusion due to the great grain refinement. Specially, higher Zn content led to the increment in yield strength and a slight reduction in elongation due to the larger fractions of second phase particles. The room temperature thermal conductivity of as-extruded alloys was also improved compared with that of as-cast counterparts. The increment of Zn content decreased the thermal conductivity of both as-cast and as-extruded alloys, which was due to the increased second phase fraction and solution atoms in the matrix, that hindering the motion of electrons. The as-extruded Mg–2Zn–0.4Ca–0.2Mn (wt%) alloy exhibited the highest elongation of 27.7% and thermal conductivity of 139.2 W/(m·K), combined with an acceptable ultimate tensile strength of 244.0 MPa. The present paper provides scientific guidance for the preparation of lightweight materials with high ductility and high thermal conductivity.
The rapid development of 5G communication inspires the demand of lightweight materials with high thermal conductivity (TC) [1–2]. Compared with commonly used materials including copper (Cu) and aluminum (Al) alloys, magnesium (Mg) and its alloys enjoy the advantages of low density (1.74 g/cm3 for pure Mg) and considerable heat dissipation performance (158 W/(m·K) for pure Mg). However, the practical application of traditional cast Mg alloys with high thermal conductivity is significantly hindered owing to their inadequate mechanical properties. To satisfy the service property under poor working conditions, further improvement of thermal conductivity and mechanical properties of Mg alloys is the challenge and target in the future research.
In recent decade, on the basis of Mg–X (X=Al, Zn, Mn, RE) binary alloys, ternary or multiple-element Mg alloys were paid increasing attention and these researches provided valuable experimental data for fabricating high-strength and high TC Mg alloys [3]. Among these Mg alloys, Mg–Zn series alloys exhibited better combination of higher strength, higher TC, and lower cost than Mg–Mn and Mg–Al and Mg–RE alloys, respectively [4–5]. In order to improve the mechanical properties and formability of Mg–Zn binary alloy, Mg–Zn–Zr, Mg–Zn–Mn(–Ce), and Mg–Zn–Cu were developed [6–10]. Combined with optimized thermomechanical processing and heat treatments, alloys with appreciating mechanical properties were successfully fabricated. However, although the tensile strength of these alloys reaches ~300 MPa, the thermal conductivity can hardly breakthrough 135 W/(m·K). Furthermore, comparatively high cost of alloying elements (e.g., Cu, Ce, Zr, etc.) and complex processing methods hinder the wide application of these alloys. Therefore, high thermal conductivity Mg alloys with acceptable mechanical properties and simple processing route are desirable for present application.
Recently, the combined addition of Zn and Ca in Mg alloys was proven to be an effective and cost-efficient method for improving both strength and formability [11–14]. The mechanical properties of Mg–Zn–Ca alloys with low-alloyed and heavy-alloyed Zn were investigated in previous studies [15–16]. For instance, the peak-aged Mg–6Zn–1Mn–2Sn–0.5Ca alloy showed an extremely high ultimate tensile strength (UTS) of 407 MPa and yield strength (YS) of 379 MPa [15]. However, the ductility of this alloy is limited by only 7.5%. A low-alloyed Mg–Zn–Ca alloy with weak texture intensity was prepared by rolling and annealing [16]. The influence of Zn content, in the range from 0.5wt% to 2wt%, on the texture and microstructure was investigated and the alloy with ~30% in elongation to failure was obtained. However, the effect of Zn content, in the range from 2wt% to 6wt%, on microstructure, mechanical properties and thermal conductivity was still unclear. This impedes the deep understanding of microstructure evolution and precise alloy design strategies for the novel high performance Mg alloys. Therefore, to balance the mechanical properties, thermal conductivity, and preparation cost, Mg–xZn–0.4Ca–0.2Mn (x = 2wt%, 4wt%, 6wt%) alloys are designed and the influence of Zn content on grain size, second phase, texture, mechanical properties, and thermal conductivity are investigated in detail in present study.
2.
Experimental
Commercial pure Mg (99.99wt%), pure Zn (99.97wt%), Mg–30wt% Ca, and Mg–10wt% Mn master alloys were used to prepare the target Mg–xZn–0.4Ca–0.2Mn (x = 2wt%, 4wt%, 6wt%) alloys. Minor Mn was added to reduce the side effect of Fe on the ingots quality as well as refining the as-cast microstructure. The raw materials were melted in an electric resistance furnace at 740°C under the protection of inert gas mixture. The melt were poured into a 316 stainless steel crucible (ϕ70 mm × 120 mm) which was preheated at 250°C after the melt liquid was maintained at 720°C for 20 min. The actual composition of the ingots was detected by inductively coupled plasma atom emission spectrometer (ICP-AES, Agilent 725) and the results are listed in Table 1.
Table
1.
Chemical composition of as-cast Mg–Zn–Ca–Mn alloys wt%
The as-cast Mg–Zn–Ca–Mn alloys were homogenized at 380°C for 26 h followed by water quenching. The extruded plates with cross section dimension of 30 mm × 5 mm were obtained by a 300T horizontal extruder with an extrusion ratio of 20:1. The extrusion was performed at a near-solidus temperature (380°C) and with an extrusion speed of 0.4 mm/s to prevent the hot tearing. After extrusion, the extruded bars were air cooled to room temperature.
The specimen for thermal conductivity test was a rectangular disk of 10 mm × 10 mm × 2 mm in size and the tested plane was parallel to the extrusion direction (ED). The thermal conductivity (λ, W/(m·K)) was obtained by the product of thermal diffusivity (α, m2/s), density (ρ, g/cm3), and specific heat capacity (cp, J/(kg·K)) at constant pressure, i.e., λ = α·ρ·cp. The thermal diffusivity was measured at room temperature using Netzsch LFA447 flash analyzer device. The density was tested by Archimedes method and the specific heat capacity was determined by differential scanning calorimeter (DSC) using sapphire as the reference specimen.
Microstructures of as-cast and as-extruded alloys were observed by optical microscope (OM, Zeiss A1) and scanning electron microscope (SEM, EM30AX) equipped with energy dispersive spectrometer (EDS). The specimens were prepared through the standard metallographic method. Also, the grain size statistics in as-cast sample and the area fraction of the second phase were measured by the image analysis software. More than 300 grains or at least 200 second phase particles in OM and SEM images were analyzed to ensure the accuracy. The grain size distribution, grain orientation, and texture observation in as-extruded samples was conducted by the electron backscatter diffraction (EBSD) on a SEM (FEI QUANTA FEG650) equipped with an EBSD detector. The SEM and EBSD specimens were both observed on the extrusion direction (ED)–transverse direction (TD) plane. Precipitation observation was performed by transmission electron microscope (TEM, FEI Tecnai F20). Selective area electron diffraction (SAED) and EDS were used to determine the precipitates. To determine the phase constitution, X-ray diffraction (XRD) analysis was performed by a Rigaku device (Miniflex 600) with Cu-Kα radiation. Flat dog-bone shaped specimens with a gauge section of 15 mm length, 3 mm width, and 2 mm thickness were used for the room temperature tensile tests. The tensile properties were tested on an electron universal machine with a strain rate of 1×10−3 s−1. The yield strength was measured by a 0.2% offset method. At least three samples were measured to guarantee the repeatability of the stress–strain curves.
3.
Results and discussion
3.1
Microstructures observation
Fig. 1 shows the OM and SEM micrographs of as-cast Mg–Zn–Ca–Mn alloys with various Zn contents. As shown in Fig. 1(a)–(c), the as-cast microstructure mainly consists of α-Mg matrix and eutectic phases. The area fraction of eutectic phase increases with Zn content in Mg–Zn–Ca–Mn alloys. In SEM images (Fig. 1(d)–(f)), the particles in bright contrast can be observed mainly at grain boundaries and form a network, while the rest of them are distributed in grain interiors. Based on EDS results (Table 2), these particles are mainly constituted by Mg, Zn, and Ca atoms. According to the atom ratios, DSC results (Fig. S1 in the supplementary information) and XRD patterns (Fig. 2), these particles are demonstrated to be Ca2Mg6Zn3 phase. MgZn and Mg7Zn3 binary phase that have been observed in Mg–Zn alloys are not detected in present Mg–Zn–Ca–Mn alloys. This result may be related to the fact that the addition of minor Ca in Mg–Zn alloys leads to the formation Ca2Mg6Zn3 phase, instead of Mg–Zn binary phases, through the eutectic reaction L → α-Mg + Ca2Mg6Zn3 [11]. The peak representing Mn-containing phase was not found in XRD patterns, owing that Mn element was mainly solid-soluted in Mg matrix. In addition, the peak intensity of Ca2Mg6Zn3 phase increases with Zn content, indicating that the amount of second phases increases with Zn content. This phenomenon can be also verified by the fact that the area fraction of second phases in as-cast ZXM200, ZXM400, and ZXM600 alloys (Fig. 1(d)–(f)) are 4.5%, 6.5%, and 8.1%, respectively.
Fig.
1.
OM (a–c) and SEM (d–f) micrographs of as-cast Mg–Zn–Ca–Mn alloys: (a, d) ZXM200; (b, e) ZXM400; (c, f) ZXM600.
Fig. 3 shows the SEM micrographs of as-extruded Mg–Zn–Ca–Mn alloys. Obviously different from the as-cast microstructure, the eutectic compounds that undissolved into the matrix during homogenization (Fig. S2) are fragmented into fine particles, forming bands along the extrusion direction in as-extruded samples. The average particle sizes of second phase in ZXM200, ZXM400, and ZXM600 alloys are 0.41, 0.67, and 0.85 μm, respectively. Prominent particle coarsening can be determined with the increase of Zn content. In addition, higher Zn content leads to a larger area fraction of second phase particles, as already revealed in Fig. 1.
Fig.
3.
SEM micrographs of as-extruded Mg–Zn–Ca–Mn alloys in (a–c) low magnification and (d–f) high magnification: (a, d) ZXM200 alloy; (b, e) ZXM400 alloy; (c, f) ZXM600 alloy.
In order to illustrate the grain size distribution in as-extruded alloys, EBSD maps on the ED–TD planes are displayed in Fig. 4(a)–(c). All the as-extruded samples present a bimodal type microstructure, where elongated coase deformed grains are embedded in the fine recrystallized (DRXed) grains matrix. This type of microstructure, usually known as heterogeneous microstructure, has been proven effective in providing superior strength–ductility synergy [17–19]. For ZXM200 alloy, the microstructure consists of mostly quasi-equiaxed DRXed grains and a few deformed grains. Increasing Zn content to 4wt%, the area fraction of deformed grains increases to 13.5% and these grains are elongated along the extrusion direction. As for ZXM600 alloy, the area fraction of deformed grains further increases to 14.6%. Unlike the results in dilute Mg–Zn–Ca alloys (Zn content < 2wt%), where the fraction of DRXed grains increases with the increase of Zn content [16], the fraction of DRXed grains in present study decreases with Zn content. This is because the higher fraction of sub-micrometer sized second phase particles present a drag effect on grain boundaries and thus hinder the recrystallization process by restricting the movement of grain boundaries.
Fig.
4.
EBSD maps (a–c) and grain size distribution (d–f) of as-extruded Mg–Zn–Ca–Mn alloys: (a, d) ZXM200 alloy; (b, e) ZXM400 alloy; (c, f) ZXM600 alloy.
Besides the area fraction of DRXed grains, Zn content also affects the average size of DRXed grains. The size distributions of DRXed grains in as-extruded samples are shown in Fig. 4(d)–(f). The average sizes of DRXed grains ( −dDRX) in ZXM200, ZXM400, and ZXM600 alloys are 5.73, 6.30, and 6.51 μm, respectively. Obviously, increasing Zn content results in only a slight increase in the size of the DRXed grains. In fact, the extrusion temperature, other than the Zn content, is the dominant role determining the average size of DRXed grains. Considering that all three samples were extruded in the same temperature, the average grain size of the DRXed grains were almost the same [20–21].
In order to further determine the texture of as-extruded alloys with different Zn contents, {0001} and {01ˉ10} pole figures (PFs) of whole regions, DRXed regions, and un-DRXed regions in Fig. 4(a)–(c) are shown in Fig. 5. The as-extruded alloys exhibit a type of basal texture where most grains orient with the {0001} planes parallel to the ED. Moreover, the DRXed regions and un-DRXed regions exhibit different texture intensities. The un-DRXed regions exhibit stronger texture intensity while the DRXed regions show much weaker texture intensity. Moreover, the texture intensity of DRXed regions decreases obviously with the increase of Zn content while the texture intensity of whole regions maintains in the range of 9–12.
Fig.
5.
Pore figures of the as-extruded Mg–Zn–Ca–Mn alloys: (a, d, g) ZXM200 alloy, (b, e, h) ZXM400 alloy, and (c, f, i) ZXM600 alloy; (a–c) the whole regions, (d–f) the DRXed regions, and (g–i) the un-DRXed regions.
Similar to the results in Mg–Zn–Ca alloys, Mg–Zn–RE alloys, and Mg–Zn–Sn alloys [14,22–23], all three samples in present study exhibit basal texture with basal pole tilted from the normal direction to the transverse direction. It has been reported that RE and Ca elements may cause the orientation departure from the conventional basal texture [22–23]. Besides, recent studies showed that the addition of Zn leads to the increase of the texture intensity [24–25].
The extrusion of Mg–Zn–Ca–Mn alloy was conducted at a relatively high temperature, during which dynamic precipitation was significantly suppressed. TEM micrographs of as-extruded ZXM200 and ZXM600 alloys are displayed in Fig. 6. Both sub-micrometer sized particles and a few nanoparticles can be found in as-extruded alloys. Based on the EDS results and the corresponding SAED patterns, the sub-micrometer sized particles (red arrows) are the Ca2Mg6Zn3 phase and these particles are the fragmented eutectic phase during extrusion. While the nanoparticles (blue arrows) are determined to be the β′-MgZn phase, which are the precipitates during the extrusion.
Fig.
6.
TEM images of the as-extruded ZXM200 (a) and ZXM600 (b) alloys and corresponding SAED and EDS results (c, d) of the second phase in the microstructure.
Although ZXM600 alloy contains higher Zn content, the density of precipitates seems no obvious difference with that in ZXM200 alloy. This may be due to that both the alloys are deformed in a near-solidus temperature. The precipitation of the β′ phase, which depends on the temperature reduction during the hot extrusion and alloying elements diffusion from the supersaturated matrix, is impeded by the higher deformation temperature. The dynamic precipitation process is of great importance for improving the tensile properties and thermal conductivity of Mg alloys. On the one hand, these nano-sized precipitates can pin the grain boundaries and retard the grain growth during the hot extrusion and the followed cooling period. Also, these precipitates can react with dislocations and thereby improve the strength of the alloys, based on the Orowan theory. On the other hand, the thermal conductivity of the alloy is mainly related to the motion of electrons. The solution atoms, precipitates, and crystal defects such as dislocations and grain boundaries can all affect the thermal conductivity. However, the effects of the precipitates on thermal conductivity are comparatively much lower than that of solution atoms because the interspace between the precipitates is much larger than the mean free path of electrons (nanoscale) [26].
3.2
Mechanical properties
Fig. 7 shows the tensile engineering stress–strain curves of as-cast and as-extruded alloys at ambient temperature and the corresponding tensile properties are listed in Table 3. The SEM images of fracture morphologies of as-cast and as-extruded alloys are presented in Fig. 8. Firstly, both the ultimate tensile strength (UTS) and yield strength (YS) of as-cast samples increase slightly with Zn content. In addition, all the as-cast samples show the elongation to failure (EL) less than 5%. As evidenced by the grain boundaries (Fig. 8(a)–(c)), the as-cast alloys exhibit a feather of brittle intergranular fracture mechanism. The low bonding strength between the coarse Mg matrix and brittle eutectic compounds leads to the initiation and propagation of the microcracks. The increase in Zn content thickens the eutectic phase between the adjacent grains, and this observation is in consistence with the SEM images of as-cast microstructure.
Fig.
7.
Stress–strain curves of (a) as-cast and (b) as-extruded Mg–Zn–Ca–Mn alloys tested at ambient temperature.
As for as-extruded samples, both the strength and elongation of Mg–Zn–Ca–Mn alloys are significantly improved compared with as-cast counterparts, i.e., the UTS, YS, and EL have increased by 76.5%, 94.8%, and 670.5%, respectively. According to the aforementioned results, grain refining of recrystallized grains and strong basal texture of deformed grains are the main strengthening mechanisms for the improvement of strength. Additionally, the great grain refinement and dispersed grain orientation distribution of DRXed grains collectively contribute the superior elongation for as-extruded alloys in this study. Furthermore, as Zn content increases, the UTS of as-extruded Mg–Zn–Ca–Mn alloys increases while the elongation reduces slightly. For instance, the UTS of ZXM600 alloy increases to ~274 MPa whereas the elongation reduces to about 25%. This may be related to the decrease of the average {0001}<11ˉ20> global Schmid factor (SF, Fig. S3). The reduction of SF of basal slip from 0.28 to 0.23 with the increase of Zn content indicates that the basal slip impediment leads to the strengthening of the sample. Moreover, the larger fraction of sub-micrometer sized second phase particles (Fig. 3) also contribute to strengthening effect, to some extent, by pinning dislocation movement. Considering that the density of nano-sized precipitates during extrusion is almost the same for as-extruded ZXM200 and ZXM600 alloys, the variations of the tensile properties are closely related to the reduction of SF and the increment of the fractions of sub-micrometer sized second phase particles.
From the fracture morphologies shown in Fig. 8(d)–(f), numerous dimples can be seen in as-extruded samples, which indicate typical ductile fracture mechanisms. A few tearing edges can also be found in the SEM images in Fig. 8(d)–(f). However, increasing Zn content seems no obvious influence on the fracture morphologies as well as the fracture mechanisms.
3.3
Thermal conductivity
Fig. 9(a) and (b) shows the variation of thermal diffusivity and thermal conductivity of Mg–Zn–Ca–Mn alloys in as-cast and as-extruded states. The corresponding values of specific heat capacity, density, and diffusivity are provided in Table 4.
Fig.
9.
Values of room temperature thermal conductivity of Mg–Zn–Ca–Mn alloys in (a) as-cast and (b) as-extruded states.
According to Fig. 9, both thermal diffusivity and thermal conductivity of as-cast alloys decrease with increasing Zn content. For instance, the as-cast ZXM200 alloy exhibits highest TC of 125.8 W/(m·K), while the as-cast ZXM400 and ZXM600 alloys show the TC of 120.9 and 107.2 W/(m·K), respectively. The similar results can also be found in as-extruded samples. The as-extruded ZXM200 alloy owns the highest TC of 139.2 W/(m·K) among all three as-extruded alloys. Obviously, higher Zn content indeed lowers the thermal diffusivity and thermal conductivity of the alloys.
Fig. 10 presents the values of EL, UTS, and TC in present alloys and Mg–Zn–Ca alloys, Mg–Zn–Zr alloys, Mg–Zn–Mn alloys, Mg–Mn alloys, and Mg matrix composites [4,6,8,27–30]. It is worthy to note that the as-extruded Mg–2Zn–0.4Ca–0.2Mn (wt%) alloys in this study exhibit superior ductility and thermal conductivity, which is even comparable with Mg composite reinforced by carbon nanotubes [30].
Fig.
10.
Comparison of thermal conductivity and mechanical properties in present study and previous studies [4,6,8,27–30].
Two main reasons may be responsible for the excellent thermal properties. First, in the view of the alloy composition, the thermal conductivity of metal is mostly depended on the electrons motion [31]. Solute atoms, dislocations, and second phase particles can all affect the free motion of electrons and therefore reduce the thermal conductivity. Among those, solute atoms have the most important influence on thermal conductivity of the alloys. In Mg–2Zn–0.4Ca–0.2Mn alloy, on the one hand, the alloying elements such as Zn, Ca, and Mn, are added in Mg matrix with low content. The lattice distortion is thus limited in a comparatively low degree. Additionally, in Mg–Zn–Ca–Mn system, the solid solubility of Ca and Mn are considerably low at ambient temperature. Generally, Zn atom has the similar atomic radius (0.153 nm) with Mg atom (0.160 nm) and is more likely to solute in Mg crystal lattice with low distortion. Although Ca has much larger atomic radius (0.197 nm) than Mg atom, Ca atom can hardly solute in Mg matrix due to the low solid solubility at ambient temperature. Besides, the co-segregation of Zn and Ca, which lowers the solid solubility of solute atoms in Mg matrix, can be found at grain boundaries through high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) techniques, and this further reduce the distortion degree raised by Zn atom [32]. Through semi-quantitatively calculating the solute Zn atom content in matrix in as-extruded alloys, on the basis of SEM-EDS method, it is found that the average atom percentages of Zn in matrix are 0.24at%, 0.46at%, and 0.81at%, respectively. Therefore, higher Zn content indeed leads to the larger fraction of Zn atom dissolved in Mg matrix, thus decreasing the thermal conductivity of the alloys.
Secondly, comparing the as-cast alloys and as-extruded alloys in present investigation, the as-extruded alloys show a higher thermal diffusivity and thermal conductivity for the same chemical composition. In fact, the hot extrusion processing route used in present study leads to the dynamic precipitation of Zn-containing phase, and this process is reported to be the key point for the slightly increased thermal conductivity [10]. Moreover, the casting defects and the continuous eutectic network in the as-cast alloys decrease the diffuse path for the electrons to a considerable extent. However, these defects have been disappeared apparently and the continuous network has been broken after the hot extrusion, leading to a higher thermal diffusivity and thermal conductivity.
4.
Conclusions
In present paper, the Mg–xZn–0.4Ca–0.2Mn (x = 2wt%, 4wt%, 6wt%) alloys were prepared and the microstructure, texture, tensile properties, and thermal conductivity of the alloys in as-cast and as-extruded states were systematically investigated. A high ductility and high thermal conductivity of Mg–2Zn–0.4Ca–0.2Mn (wt%) alloy was obtained. Main conclusions are as follows:
(1) The as-cast Mg–xZn–0.4Ca–0.2Mn (x = 2wt%, 4wt%, 6wt%) alloys consist of α-Mg matrix and Ca2Mg6Zn3 eutectic phase locating at grain boundaries. The area fraction of second phase increases from 4.5% for ZXM200 alloy to 8.1% for ZXM600 alloy.
(2) The as-extruded alloys exhibit a bimodal structure which consists coarse deformed grains with strong basal texture intensity and fine DRXed grains with much random orientation. Fine grain strengthening and texture strengthening are the main strengthening mechanisms in present alloys. With the increase of Zn content, the strength increases whereas the ductility reduces slightly because of the variation of basal slip SF and the increment of the second phase fraction.
(3) Zn content exhibits significant effect on the thermal conductivity of Mg–Zn–Ca–Mn alloys. For as-extruded Mg–Zn–Ca–Mn alloys, with increasing Zn content, the thermal conductivity decreases from 139.2 to 119.5 W/(m·K) due to the increment of fraction of solute atoms and second phase particles.
(4) The as-extruded Mg–2Zn–0.4Ca–0.2Mn alloy exhibits balanced comprehensive properties with ultimate tensile strength of 244.0 MPa, yield strength of 149.5 MPa, elongation to failure of 27.7%, and thermal conductivity of 139.2 W/(m·K).
Acknowledgements
This work was supported by the Natural Science Basic Research Program of Shaanxi, China (Nos. 2022JQ-305 and 2022JQ-326) and the Qin Chuang Yuan Platform High-Level Talent Project of Innovation and Entrepreneurship (No. QCYRCXM-2023-020).
Conflict of Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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