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Article

The Microstructural Observation in Precipitations of Peak-Aged Al–Zn–Mg Alloys with Various Zn/Mg Ratios

by
Wanlalak Sanphiboon
1,
Seungwon Lee
2,
Taiki Tsuchiya
2,
Abrar Ahmed
3,
Susumu Ikeno
2,
Tomoo Yoshida
1,4 and
Kenji Matsuda
2,3,*
1
Graduate School of Science and Engineering, University of Toyama, Toyama 930-8555, Japan
2
Faculty of Sustainable Design, University of Toyama, Toyama 930-8555, Japan
3
Advanced Aluminum International Research Center, University of Toyama, Toyama 930-8555, Japan
4
AISIN Keikinzoku Co., Ltd., Toyama 934-8588, Japan
*
Author to whom correspondence should be addressed.
Metals 2025, 15(11), 1260; https://doi.org/10.3390/met15111260
Submission received: 16 October 2025 / Revised: 12 November 2025 / Accepted: 14 November 2025 / Published: 18 November 2025
(This article belongs to the Section Metal Casting, Forming and Heat Treatment)
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Abstract

The precipitation behavior of peak-aged Al–Zn–Mg alloys with various Zn/Mg ratios was investigated to clarify the relationship between aging microstructure and mechanical response using (scanning) transmission electron microscopy (STEM/TEM). The results revealed that both aging temperature and Zn/Mg ratio significantly influence the type, size, and density of precipitates, thereby determining the alloy hardness. At higher temperatures, coarser and lower-density precipitates led to reduced hardness, while finer and denser precipitates formed at lower temperatures enhanced hardening. For alloys with Zn/Mg < 1.0, the T′/T phases dominate strengthening, whereas η′/η phases are predominant for Zn/Mg > 2.0. Moreover, this study identifies a novel type of precipitate aligned along [110] Al in high-Mg alloys aged at 120 °C, which has not been reported previously and may contribute additional strengthening. These findings provide new insight into the compositional and thermal control of precipitation mechanisms in Al–Zn–Mg alloys.

1. Introduction

Increasing political awareness and the growing emphasis on economic sustainability have accelerated the development of advanced and sustainable materials as solutions to meet the decades’ CO2 emissions. The utilization of low-density alloys, particularly aluminum alloys, in lightweight structural design is a well-established approach to achieving weight reduction and, consequently, lowering emissions [1]. Among these, the Al–Zn–Mg alloy system contributes a set of medium-to-high-strength age-hardenable aluminum alloys that derive their strength primarily from the precipitation of metastable, semi-coherent, nano-sized precipitates during artificial aging (AA) [2,3]. The predominant strengthening phase in these alloys is η′ (MgZn2). The Zn/Mg atomic ratio strongly influences the precipitation behavior in Al–Zn–Mg alloys. If the Zn/Mg ratio exceeds 2, η′ and η phases tend to form preferentially; conversely, when the ratio is below 2, T′ and T phases are more dominant [4]. Al–Zn–Mg alloys with a very low Zn/Mg ratio (or less than 1) often exhibit enhanced strength due to the presence of Zn-Mg clusters and precipitates, which can locally deplete Mg and thereby suppress dynamic strain aging. Zn-modified Al-Mg alloys also display a pronounced hardening response associated with T-phase precursors, typically following an initial incubation period before significant hardening occurs [5,6,7].
Age-hardenable Al alloys, including Mg and Cu, Si, or Zn, form Guinier–Preston (GP) zones and a metastable phase before precipitation of the equilibrium phase [8]. In Al–Zn–Mg alloys, the earliest stage of aging involves the formation of Guinier–Preston (GP) zones, coherent clusters of solute atoms that precede the formation of η′ and η phases [9]. The lower temperature was chosen to promote η-phase formation [10,11], consistent with prior reports that GP zones begin to form near this temperature. In contrast, the higher temperature was selected based on evidence that solid precipitates start to form around 170 °C, and with further temperature increase, they grow and transform into more stable phases, leading to coarsening and a reduction in hardness [11,12]. Despite these studies, the relationships among Zn/Mg ratio, aging temperature, and resultant hardness remain insufficiently clarified.
In the present study, aluminum alloys representative of the 7xxx series compositions were designed, keeping the total Zn + Mg content approximately 6–7 mol%. Two compositions with Zn/Mg ratios of 0.40 and 2.5 were selected to investigate the effect of precipitation behavior and peak-aging hardness at the aging temperatures of 120 °C and 200 °C. Although it would be sufficient to correlate the microstructural evolution and hardness with respect to aging time, the present study focuses specifically on the peak-aged condition to clarify the relationship between precipitation characteristics and maximum hardening response.

2. Materials and Methods

The alloys were prepared using high-purity aluminum (99.99%, square ingots approximately 5–10 mm in thickness and up to 30 cm in length), zinc (99.9%, irregularly shaped pieces), and magnesium (99.9%, irregular chips). The raw materials were weighed according to the designed compositions, charged into a graphite crucible, and melted in a permanent steel mold under an air atmosphere (ambient air without protective gas). The melt was gently stirred to ensure compositional homogeneity before solidification. The resulting ingots were homogenized at 450 °C for 24 h to eliminate chemical segregation. The alloys were designed as ZM16, ZM25, and ZM52, where “Z” and “M” denote zinc (Zn) and magnesium (Mg), respectively. The numerical codes correspond to the molar percentages of Zn and Mg in each composition. ZM16, ZM25, and ZM52 contained 1.5 mol%, 2.1 mol%, and 4.8 mol% Zn, and 5.8 mol%, 5.2 mol%, and 1.93 mol% Mg, respectively, as summarized in Table 1. The alloy compositions were designed with reference to equilibrium phase diagrams calculated via thermodynamic simulations carried out with Thermo-Calc software (version 2024a, Thermo-Calc Software AB, Stockholm, Sweden). The predicted phase equilibria at 120 °C and 200 °C are shown in Figure 1a and Figure 1b, respectively. It was expected that the alloy with a low Zn/Mg ratio (ZM25, Zn/Mg = 0.40) would favor T phase formation in the Al matrix, while the alloy with a high Zn/Mg ratio (ZM52, Zn/Mg = 2.50) would promote more η phase formation (see Table 1). The T phase contributes moderate hardening, whereas the η′/η phases provide stronger precipitation strengthening due to their finer size and higher coherency with the Al matrix. Moreover, thermodynamic calculations indicated that the types of precipitates are comparable across both aging temperatures.
Sheets with a thickness of approximately 1.5 mm and a width of 15 mm were hot-extruded at around 400 °C and subsequently cold-rolled to a final thickness of 1.0 mm. The rolled sheets were subjected to heat treatment, put in solution at 475 °C for 60 min in an air furnace, followed by quenching in ice water with approximately 5 °C. Artificial aging was conducted at 120 °C and 200 °C in a silicone oil bath. The aging treatments were carried out in a temperature-controlled silicone oil bath (±3 °C accuracy) at 120 °C and 200 °C. The samples were immersed after quenching and held isothermally for predetermined times ranging from 2 min to 100,000 min. After aging, the specimens were rapidly quenched in water to preserve the microstructure. Figure 2 shows the relationship graph between micro-Vickers hardness and aging time for ZM25 and ZM52 alloys subjected to aging treatments at 120 °C and 200 °C. Hardness measurements were performed using a Mitutoyo HM-101 (Mitutoyo Corporation, Kanagawa, Japan) with a loading of 9.8 N, holding for 15 s. For transmission electron microscopy (TEM) observations, the aged alloy foils were mechanically and electrochemically polished in a solution of 1-part perchloric acid and 9 parts ethanol, thinned to approximately 0.08 μm. Final thinning was performed using single-jet electrolytic polishing in a solution of 1 part nitric acid and 2 parts methanol at 25 °C to locally produce thinner regions. The foils were then further polished at approximately 5 °C until a small perforation was formed. Circular discs with a diameter of 3 mm were subsequently punched around the perforated area using a precision disc cutter. TEM observations were conducted in the thin region adjacent to the perforation, where electron transparency is optimal. TEM analyses were carried out using a Topcon EM-002B microscope (ARIM Japan, Tsukuba, Japan) at an acceleration voltage of 120 kV to obtain high-resolution TEM (HRTEM) images and selected area diffraction (SAED) patterns. Higher-resolution imaging was performed using a Thermo Scientific Talos F200X-G2 (Waltham, MA, USA) scanning transmission electron microscope (STEM) operated at 200 kV, with a dwell time of 500 ns and a field of view (FOV) of 18 nm.

3. Results

3.1. Vickers Microhardness

The Vickers microhardness results are presented in Figure 2. The as-quench hardness of both alloys is shown for comparison. The ZM52 alloy exhibited a higher hardness than ZM25, which can be attributed to solid-solution strengthening. This is consistent with previous findings indicating that higher Zn/Mg ratios result in increased as-quenched hardness due to greater Zn retention in solid solution, thereby enhancing solid-solution hardening and mechanical strength [13,14]. Consequently, it can be inferred that ZM52 tends to form solute clusters more rapidly than ZM25. For the ZM52 alloy, both aging temperatures (120 °C and 200 °C) resulted in slightly different peak hardness values; however, the time required to reach peak aging was significantly shorter at 200 °C. In contrast, the ZM25 alloy exhibited distinct aging behavior. At 200 °C, the hardness increased slightly to a modest peak before gradually decreasing, whereas at 120 °C, the hardness remained nearly constant for an extended period and then increased sharply to reach the peak value, followed by a continuous decline.
The difference between the peak-aging hardness and the as-quench hardness values represents the age-hardening response was found to be strongly dependent on the aging temperature. At 120 °C, the age hardening response was comparable between the high and low Zn/Mg alloys. Conversely, at 200 °C, the high Zn/Mg alloy (ZM52) exhibited a markedly higher hardening response than the low Zn/Mg alloy (ZM25), as illustrated in Figure 7b.

3.2. TEM Observation

TEM observations were conducted under the peak-aged conditions for all four aging treatments, specifically for the ZM25 and ZM52 alloys aged at 120 °C and 200 °C, respectively. The primary correlations between microstructure and hardness were examined in terms of precipitate density and the relative fractions of η′/η, T′/T, and other secondary precipitates. Representative bright-field images, selected area electron diffraction (SAED) patterns, and corresponding schematic illustrations based on the SAED patterns shown in the white box are presented in Figure 3a–c and Figure 3d–f for aging at 200 °C, and in Figure 4a–c, Figure 4d–f, and Figure 4g–i for aging at 120 °C, respectively. The diffraction spots in the SAED pattern were identified by reference to the previous research [15,16,17,18]. The type and morphology of precipitates observed in the bright-field images were determined according to established relationships and morphologies [1,18,19,20,21,22,23]. At the aging temperature of 200 °C, the SAED pattern along the <100> Al zone axis revealed the presence of two main types of precipitates. For ZM25 alloy (Figure 3b), the SAED pattern exhibited a strong reflection corresponding to the T and T′ phases [15,16,17,18]. The distance from the 000Al-1/2 022 Al distance, which was taken as 1.0 (Figure 3c). The dashed lines showed dimensions. The corresponding bright-field image (Figure 3a) showed a high number density of fine cubic-shaped T/T′ precipitates with an average diameter of approximately 7.0 nm. In contrast, the SAED pattern for the high-Zn alloy ZM52 (Figure 3e), projected along the <110> Al zone axis, exhibited strong reflections corresponding to η′ precipitates. The distance from 000Al-1/2 022 Al distance of 1.0 [24,25], as illustrated in Figure 3f. The bright-field image of ZM52 aged at 200 °C (Figure 3d) revealed a dense distribution of fine η and η′ precipitates with an average diameter of approximately 5.5 nm. Compared with ZM25 aged under the same conditions, the precipitates in ZM52 were smaller and more finely dispersed.
On the contrary, aging at 120 °C revealed three distinct types of precipitates, as identified from the SAED patterns along the <100> Al zone axis. For ZM25 (Figure 4b), the SAED pattern exhibited strong diffraction spots corresponding to the T′, T, and η′ phases. The distances from the 000 Al spot to the T/T′ and η′ reflections were approximately 0.81 and 0.65, respectively, relative to the 000Al–1/2 022 Al distance of 1.0, as illustrated in Figure 4c [15,16,17]. In addition, an unidentified streak was observed at an angle of approximately 45° from the [100] Al direction, suggesting the presence of an additional, unidentified type of precipitate. The corresponding bright-field image (Figure 4a) revealed a high number density of T/T′ precipitates with an average diameter of approximately 25 nm. Other observed phases included η′/η precipitates and unidentified particles aligned along the [110] Al and [1 1 ¯ 0] Al directions. These unidentified precipitates were characterized as novel precipitates. For the ZM52 alloy aged at 120 °C, SAED patterns projected along the <100> Al direction (Figure 4e) showed stronger diffraction intensity than those of ZM25 under the same conditions, indicating a higher precipitate density. Diffraction spots corresponding to the T′, T, and η′ phases were clearly visible; however, the unidentified streaks observed in ZM25 were absent. The bright-field image (Figure 4d) confirmed the presence of dense T′/T and η′ precipitates with a higher number density than both ZM25 aged at 120 °C and ZM52 aged at 200 °C. No novel precipitates were observed in this condition. Furthermore, the SAED patterns of <110> Al zone axis for ZM52 (Figure 4h) exhibited distinct η′ diffraction spots, similar to those observed at 200 °C (Figure 3e), but with additional streaking associated with η′ phases. The bright-field image (Figure 4g) showed a greater lateral extent of η/η′ precipitates, with an average diameter of approximately 7.0 nm, compared with the projecting from the <100> Al direction.
Since some T′/T phases have exhibited similar orientations to the novel precipitates, a higher-resolution investigation was conducted using STEM–HAADF imaging projected along the <100> Al direction, as shown in Figure 5a. The T/T′ phases, η phase, and novel precipitates were clearly observed. In Figure 5b, the novel precipitates are shown aligned along the [110] Al direction, observed at higher magnification. Two possible periodic unit-cell configurations were identified within the precipitate, labeled as square-i and square-ii. Each unit cell exhibited a side length of approximately 0.86 nm, corresponding to three layers of (022) Al planes, yielding a total repeat distance of approximately 0.859 nm. The fast Fourier transform (FFT) pattern of the image in Figure 5b is presented in Figure 5c. Streaks extending at 45° relative to the [100] Al direction were observed, consistent with the streaks attributed to the novel precipitates in the SAED pattern (Figure 4c). The FFT spacing between the streaks and diffraction spots was measured to be 0.0477 nm−1. Since FFT spacing represents the reciprocal of the real-space distance, the combination of six precipitate-spot spacings within one (022) Al layer, multiplied by three layers, yields an approximate periodic distance of 0.859 nm. This value agrees closely with the measured lengths of square-i and square-ii. Similarly, the image in Figure 5d presents novel precipitates aligned along the [1 1 ¯ 0] Al direction, showing comparable structural periodicity and streak features to those aligned along [110] Al.
For comparison, the precipitates that were observed in ZM25—including T′/T, η′/η, and novel precipitates were also identified in another low Zn/Mg Al–Zn–Mg alloy, designated ZM16. The ZM16 alloy was selected to compare its microstructure with that of ZM25 aged at 120 °C. The TEM bright-field image projected along the <100> Al direction (Figure 6a) revealed the coexistence of T′/T, η′/η, and novel precipitates, consistent with the corresponding SAED pattern shown in Figure 6b. At higher resolution, STEM–HAADF imaging of the peak-aged ZM16 alloy aged at 120 °C (Figure 6c) confirmed the presence of similar precipitate types. However, the precipitates in ZM16 were larger and had a lower number density than those in ZM25 under the same aging condition. This observation suggests that alloys with lower Zn/Mg ratios tend to form similar types of precipitates as those with higher ratios. Still, the number density of these precipitates increases with increasing Zn content.

4. Discussion

The correlation between TEM observations and aging hardening ability is summarized in Figure 7. As shown in Figure 7a, the number density of precipitates increases with increasing Zn/Mg ratio at both aging temperatures. Previous studies have similarly reported that the Zn/Mg ratio significantly influences precipitate density and, consequently, mechanical strength. For instance, Jiang et al. [26] observed systematic variations in precipitate number density with changing Zn/Mg ratio in Al–Zn–Mg alloys. They reported that decreasing the Zn/Mg ratio led to a lower proportion of recrystallization, a reduced volume fraction of secondary phases, and a notable decrease in the size of η′ precipitates within the grain interior.
Metals 15 01260 g007
Figure 7. The relationship between Zn/Mg and (a) the number density, (b) age hardening ability, the percentage of precipitation aged at (c) 120 °C, and (d) 200 °C.
Figure 7. The relationship between Zn/Mg and (a) the number density, (b) age hardening ability, the percentage of precipitation aged at (c) 120 °C, and (d) 200 °C.
Metals 15 01260 g007
In the present work, the observed increase in precipitate number density at both aging temperatures corresponds well with the trend of the age-hardening response. However, at 120 °C, the hardness increased only slightly as the Zn/Mg ratio rose from 0.4 to 2.5, indicating that precipitate number density exerts a weaker influence on hardness at lower temperatures than at 200 °C. This relatively weak dependence can be explained by the findings of Wang et al. [27], who discussed the relationship between particle morphology and strengthening effectiveness. They emphasized that alloys containing coherent, ordered precipitates within a disordered solid-solution matrix exhibit superior mechanical properties. Therefore, at lower aging temperatures, the coherence and morphology of precipitates may play a more dominant role in strengthening than their number density.
In contrast, at higher aging temperatures—specifically 200 °C in the present work—the dominant strengthening mechanism arises from non-shearable precipitates, which promote Orowan bypassing. Under these conditions, the number density of precipitates becomes the principal factor for dominant strengthening [28]. Accordingly, the relationship between Zn/Mg ratio and the volume fraction of precipitates aged at 120 °C and 200 °C was quantified, as shown in Figure 7c and Figure 7d, respectively. TEM observations of ZM52 indicate that η′ and η phases are the main strengthening phases, which is consistent with previous studies identifying these phases as the primary strengthening phases in Al–Zn–Mg alloys [11,29,30,31]. In ZM52, variations in precipitate size and number density were evident across the two aging temperatures. At 120 °C, aging produced finer and more densely distributed precipitates than at 200 °C. Nonetheless, aging at 200 °C resulted in higher hardness over a shorter period, due to enhanced diffusion and accelerated precipitation kinetics at elevated temperatures [31]. The novel precipitates observed in ZM16 and ZM25 suggest that these phases are specific to high-Mg Al–Zn–Mg alloys aged at lower temperatures, as they were not detected in ZM52 or at 200 °C. In ZM25 and ZM16, a larger number of T′/T phases were also identified, implying that the T′/T phase acts as the main strengthening precipitate in these compositions. This observation aligns with the findings of Ishii et al. [32], who reported that in Al–Mg–Zn alloys with relatively low Zn/Mg ratios, the T phase (T = Al6Mg11Zn11) serves as the dominant strengthening phase. The present results further indicate that when the T-phase fraction remains stable, it contributes significantly to hardness through sustained strengthening during aging. At 120 °C, additional precipitates, including a small fraction of η′/η phases and novel precipitates, are likely to co-precipitate alongside the T′/T phase, thereby influencing hardness [3,16,31]. Since the age-hardening response between ZM25 and ZM52 differs only slightly, it is inferred that co-precipitation among multiple types of precipitates plays a substantial role in determining the overall hardness.

5. Conclusions

In conclusion, Al–Zn–Mg alloys with varying Zn/Mg ratios of 0.40 (ZM25) and 2.50 (ZM52) were investigated to clarify the effects of Zn/Mg ratio on precipitation behavior and hardness.
  • According to the Vickers Hardness results, the ZM52 alloy exhibits higher as-quenched hardness than ZM25. While both alloys show comparable age-hardening responses at 120 °C, the difference becomes more obvious at 200 °C. ZM52 achieves significantly greater hardening, whereas ZM25 exhibits only a slight increase followed by gradual softening. ZM52 also shows faster cluster formation and reaches peak hardness earlier, particularly at 200 °C.
  • Based on the peak-aging conditions observed for each alloy, TEM analyses revealed that increasing the aging temperature leads to a lower number density but larger precipitate size, resulting in reduced hardness. Conversely, at lower aging temperatures, precipitates become finer and more densely distributed, which enhances hardness. However, the effect of aging temperature varied depending on the Zn/Mg ratio. In the ZM25 alloy, the precipitate areal density at 200 °C was approximately five times lower than that at 120 °C, whereas in ZM52 it decreased by only about 1.5 times. The average precipitate size in ZM25 increased nearly sixfold when the aging temperature was raised from 120 °C to 200 °C, while ZM52 showed only a slight change in precipitate size between the two temperatures.
  • Alloys with Zn/Mg < 1.0 (ZM25) aged at both 120 °C and 200 °C primarily contain T′/T phases as the dominant strengthening precipitates, followed by η′/η phases. The variation in their number density influences the resulting hardness. In contrast, the high-Zn/Mg alloy (ZM52, Zn/Mg > 2.0) predominantly forms η′/η phases as the main strengthening precipitates at both temperatures.
  • Unique precipitates aligning along [110] Al and [1 1 ¯ 0] Al were identified in high-Mg alloys (ZM25) aged at 120 °C. Their presence and relatively high number density suggest that these “novel precipitates” may contribute to the overall strengthening behavior in low-Zn/Mg alloys.

Author Contributions

Conceptualization, W.S., T.Y. and K.M.; methodology, S.L., T.T., A.A. and W.S.; software, A.A.; validation, W.S., S.L., T.T. and A.A.; formal analysis, W.S., S.L., T.T. and A.A.; investigation, W.S., T.T. and A.A.; resources, S.L., T.T., T.Y. and K.M.; data curation, W.S., T.T. and S.I.; writing—original draft preparation, W.S. and K.M.; writing—review and editing, K.M., S.L., T.Y., S.I. and A.A.; supervision, T.Y. and K.M.; project administration, K.M.; funding acquisition, K.M. All authors have read and agreed to the published version of the manuscript.

Funding

A part of this research was supported by COI-NEXT, JST.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Acknowledgments

The authors thank the Aluminum Research International Center (ARC), University of Toyama.

Conflicts of Interest

Author Tomoo Yoshida was employed by the company AISIN Keikinzoku Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Figure 1. Calculated isothermal section of the phase diagram in the Al–Zn–Mg system at (a) 120 °C and (b) 200 °C.
Figure 1. Calculated isothermal section of the phase diagram in the Al–Zn–Mg system at (a) 120 °C and (b) 200 °C.
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Figure 2. The relationship between micro-Vickers hardness and aging time for ZM25 and ZM52 alloys subjected to aging treatments at 120 °C and 200 °C.
Figure 2. The relationship between micro-Vickers hardness and aging time for ZM25 and ZM52 alloys subjected to aging treatments at 120 °C and 200 °C.
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Figure 3. (a–c) Bright-field TEM image, SAED pattern, and corresponding schematic illustration based on the SAED pattern of ZM25 alloy projected along <100> Al; (d–f) corresponding results for ZM52 alloy projected along <110> Al, both at the peak-aged condition at 200 °C.
Figure 3. (a–c) Bright-field TEM image, SAED pattern, and corresponding schematic illustration based on the SAED pattern of ZM25 alloy projected along <100> Al; (d–f) corresponding results for ZM52 alloy projected along <110> Al, both at the peak-aged condition at 200 °C.
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Figure 4. (a–c) Bright-field TEM image, SAED pattern, and corresponding schematic illustration based on the SAED pattern of ZM25 alloy projected along <100> Al; (d–f) corresponding results for ZM52 alloy projected along <100> Al; and (g–i) results for ZM52 alloy projected along <110> Al, all at the peak-aged condition at 120 °C.
Figure 4. (a–c) Bright-field TEM image, SAED pattern, and corresponding schematic illustration based on the SAED pattern of ZM25 alloy projected along <100> Al; (d–f) corresponding results for ZM52 alloy projected along <100> Al; and (g–i) results for ZM52 alloy projected along <110> Al, all at the peak-aged condition at 120 °C.
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Figure 5. (a) ZM25 aged at 120 °C at low magnification, (b) novel precipitates align on <110> Al, (c) the corresponding FFT pattern with (b), (d) novel precipitates align on <1 1 ¯ 0> Al, (e) the corresponding FFT pattern with (d).
Figure 5. (a) ZM25 aged at 120 °C at low magnification, (b) novel precipitates align on <110> Al, (c) the corresponding FFT pattern with (b), (d) novel precipitates align on <1 1 ¯ 0> Al, (e) the corresponding FFT pattern with (d).
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Figure 6. (a) TEM bright field image projected from <100> Al, (b) the corresponding SAED pattern of (a), (c) STEM image of ZM16 aged at 120 °C peak-aging.
Figure 6. (a) TEM bright field image projected from <100> Al, (b) the corresponding SAED pattern of (a), (c) STEM image of ZM16 aged at 120 °C peak-aging.
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Table 1. The chemical composition of the alloys.
Table 1. The chemical composition of the alloys.
Alloymol%wt%Al
ZnMgZn/MgZn + MgZnMgZn/MgZn + Mg
ZM161.55.80.267.33.55.10.688.6Bal.
ZM252.15.20.407.34.94.61.19.5Bal.
ZM524.81.92.56.7111.66.88.4Bal.
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MDPI and ACS Style

Sanphiboon, W.; Lee, S.; Tsuchiya, T.; Ahmed, A.; Ikeno, S.; Yoshida, T.; Matsuda, K. The Microstructural Observation in Precipitations of Peak-Aged Al–Zn–Mg Alloys with Various Zn/Mg Ratios. Metals 2025, 15, 1260. https://doi.org/10.3390/met15111260

AMA Style

Sanphiboon W, Lee S, Tsuchiya T, Ahmed A, Ikeno S, Yoshida T, Matsuda K. The Microstructural Observation in Precipitations of Peak-Aged Al–Zn–Mg Alloys with Various Zn/Mg Ratios. Metals. 2025; 15(11):1260. https://doi.org/10.3390/met15111260

Chicago/Turabian Style

Sanphiboon, Wanlalak, Seungwon Lee, Taiki Tsuchiya, Abrar Ahmed, Susumu Ikeno, Tomoo Yoshida, and Kenji Matsuda. 2025. "The Microstructural Observation in Precipitations of Peak-Aged Al–Zn–Mg Alloys with Various Zn/Mg Ratios" Metals 15, no. 11: 1260. https://doi.org/10.3390/met15111260

APA Style

Sanphiboon, W., Lee, S., Tsuchiya, T., Ahmed, A., Ikeno, S., Yoshida, T., & Matsuda, K. (2025). The Microstructural Observation in Precipitations of Peak-Aged Al–Zn–Mg Alloys with Various Zn/Mg Ratios. Metals, 15(11), 1260. https://doi.org/10.3390/met15111260

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