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Article

Al-5Er-Ti Master Alloy with Both Grain Refinement and Microalloying Effects

by
Jingrui Ma
,
Zhiguo Lei
,
Shengping Wen
*,
Guang Yang
,
Wu Wei
,
Hui Huang
* and
Zuoren Nie
School of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China
*
Authors to whom correspondence should be addressed.
Metals 2025, 15(1), 43; https://doi.org/10.3390/met15010043
Submission received: 4 December 2024 / Revised: 27 December 2024 / Accepted: 2 January 2025 / Published: 5 January 2025

Abstract

:
The phase structure, grain refinement, and microalloying effect of the Al-5Er-Ti master alloy were analyzed by a refining experiment, microhardness test, OM, SEM, and XRD. The results show that when the Er/Ti atomic ratio is 2.7, the refining effect of the Al-5Er-0.5Ti master alloy is significantly better than Al-5Er, which is due to the Ti2Al20Er phase. There are three crystal orientations of Ti2Al20Er and α-Al that satisfy the E2E model, among which (620)Ti2Al20Er<260>Ti2Al20Er//(111)Al<110>Al is the least mismatched one. When the Er/Ti atomic ratio is reduced to below 1.3, the Ti-containing phase of the Al-5Er-Ti master alloy is composed of Ti2Al20Er and Al3Ti. The primary phase size of the Al-5Er-1.5Ti master alloy decreases with the increase in cooling rate, and the grain refining effect improved more significantly. The optimum size of the Ti2Al20Er phase and Al3Ti phase is 6.0 μm and 9.5 μm, respectively. The grain size of pure aluminum is reduced from 14,000 μm to 300 μm by Al-5Er-1.5Ti master alloy refinement, and the refinement rate is 97.9%. Direct aging of the refined sample did not have a precipitation strengthening effect. After the solution and aging treatment, the peak aging of the refined sample was reached in 15 min, and the microhardness increased by 41%.

1. Introduction

A master alloy is a special type of alloy that uses the main alloying element as the matrix and adds one or more alloying elements to solve the problems of low-melting-point alloying elements being easily burned and high-melting-point alloying elements being difficult to dissolve and prone to segregation. Master alloys can be divided into the following types according to their usage: master alloys used for alloying, master alloys used for grain refinement, master alloys used for modification, and master alloys used for purification. Currently, many master alloys only serve a single purpose. For example, A-lTi-B and other grain refining intermediate alloys are mainly used for grain refinement. Mater alloys such as Al-Er and Al-Sc are mainly used for microalloying [1,2,3,4,5,6]. If a master alloy can be designed and combined with its refinement and microalloying effects, it will be able to better utilize the role of the master alloy.
The keys to producing a good refining effect of the master alloys are the following points. First of all, the crystal orientation of the primary phase and the aluminum matrix must be well matched [7,8,9]. That is, the mismatch of interplanar spacing and atomic spacing between the primary phase and the matrix is within 6% and 10%, respectively [10]. Tetragonal structure Al3Ti is a very good heterogeneous nucleation particle for α-Al, with the interplanar spacing mismatch and atomic spacing mismatch of the (112)Al3Ti<110>Al3Ti//(111)Al<110>Al orientation being less than 1.6% [10]. Secondly, the primary phase has a high melting point, which can exist stably when melted at a certain temperature and will not dissolve quickly [11]. In addition, the refining effect is very sensitive to the size of the primary phase, and a smaller primary phase has a better grain refining effect [12,13,14,15,16,17]. By means of ultrasonic stirring [18], warm rolling [19], cold rolling, and equal-channel angular pressing [12], the size control of an Al-5Ti-1B master alloy was carried out in the material preparation or plastic deformation stage, so that Al3Ti and TiB2 particles with a small size could be obtained, thereby achieving better grain refinement [12,13,18]. Adding a grain refinement master alloy and assisting with the use of external fields such as electromagnetic and ultrasound can further refine the grain size [20,21]. For example, in the presence of an electromagnetic field, a substantial reduction in grain size and the macrosegregation of alloying elements was achieved [20].
Wen et al. [21] systematically studied the effect of different contents of an Er element on the microstructure of a cast Al-Mg-Mn-Zr alloy. By analyzing the microstructure and XRD results, it was found that the α-Al grain size did not decrease when the addition amount was less than 0.2 wt%, which indicated that it was difficult for Er to produce a grain refinement effect in the form of solid solution atoms. When the addition amount was increased to 0.25 wt%, the grain size of α-Al was significantly reduced and resulted in the appearance of primary phase Al3Er [22]. The grain size continued to decrease when the addition amount was 0.4 wt%. The refining effect was not significantly improved by further increasing the amount of added Er beyond 0.4% [21,23]. These results indicate that the Al3Er primary phase has the effect of grain refinement. Because the mismatch between Al3Er and α-Al is 4.1%, Al3Er has the potential for grain refinement of aluminum alloys. In addition to grain refinement in the Er-added alloys, the mechanical properties can also be improved by precipitation of nano-phase Al3Er during heat treatment [24]. Moreover, although Al will be effectively refined by Al-Ti-B master alloys, the excessive Ti will inevitably be introduced into the Al matrix after refinement, which will reduce the electrical conductivity [25,26]. If an Al-Er master alloy can be designed for grain refinement, it will be a good choice for the improvement of the properties of aluminum conductors.
The above research shows that the addition of Er can refine the grain of aluminum alloys, but the required amount is large, which exceeds the optimal amount of Er for microalloying. Therefore, it is very important to study Er-containing master alloys that can achieve grain refinement under the condition of reducing the amount of Er. In this paper, the influence of varying Ti element contents on the phase structure and refining effect of an Al-5Er-Ti master alloy is investigated. The primary phase size is regulated by controlling the cooling rate through the thickness of the ingot, and the grain size of the refined pure aluminum is analyzed to characterize its grain refinement effect. In order to verify the hypothesis that the primary phase can be dissolved into the matrix during solid solution treatment and precipitate out nano particles to play a strengthening role, direct aging and solid solution aging heat treatments were carried out on the refined samples, respectively.

2. Materials and Methods

The preparation of Al-1.5Ti, Al-5Er, and Al-5Er-Ti master alloys was carried out in the resistance furnace VBF-1200X produced by Kejing Company in Hefei, China. High-purity aluminum (99.99 wt%), Al-6 wt%Er, and Al-10 wt%Ti master alloys are used as raw materials, and the raw materials are prepared according to the design composition. Raw material melted at 1100 °C was casted into a steel mold at room temperature and air cooled to the ambient temperature to obtain a cast with a size of 200 × 100 × 5 mm3. In order to study the effect of the cooling rate on the primary phase size and grain refinement ability, Al-5Er-1.5Ti master alloy ingots with different thickness of 5 mm, 12 mm, and 22 mm were prepared to regulate the cooling rate. The solidification process was simulated by AnyCasting software (v6.7), and the corresponding cooling rates were 0.8 °C/s, 1.9 °C/s, and 33.2 °C/s for 5 mm, 12 mm, and 22 mm thick ingots, respectively. The results of ICP (Inductively Coupled Plasm Spectroscopy) which is manufactured by PerkinElmer Inc. (in Waltham, MA, USA) were used to determine the actual composition of the ingots, as shown in Table 1. Unless otherwise stated, all components in this article are expressed as a mass percent. The master alloy samples were mechanically ground, manually polished, and electrolytically polished, and alcohol was used for drying. The D8 Advance X-ray diffractometer, which is equipped with a Cu target, is produced by the Bruker Company in Germany to analyze the phase composition of the master alloy, and the observed sample is the master alloy sample.
Refining experiments were carried out in the same resistance furnace. Melting of 750 g high-purity aluminum at 955 °C was conducted, and then the temperature was decreased to 705 °C for 3 min to keep the temperature of the aluminum melt stable. The master alloy is added to the aluminum melt and stirred for 20 s, and the holding time is up to 4 h. Samples at a certain interval (10, 30, 60, 120, and 240 min), were cast into a cylindrical steel mold with a thickness of 5 mm. The cylindrical refined sample with a size of φ60 × 20 mm3 was obtained, and 2 wt% of the Al-Er-Ti master alloy was introduced into the Al melts. The cylindrical refined sample was machined 5 mm from the bottom and then manually ground to 1000# with silicon carbide sandpaper. Then, it was deeply etched in Boyle solution (120 mL HCl + 60 mL HNO3 + 10 mL HF + 10 mL H2O) for 1–6 min, rinsed with water, and air-dried with alcohol to prepare the samples for the macroscopic morphology observation. The Olympus optical microscope with the polarized light mode was used to observe the metallographic structure of the refined sample. Some refined samples were electrolytically polished and coated for polarizing metallographic observation. The electrolytic polishing voltage is 30 V, the current is 0.6 A, and the polishing time is 25 s. The film coating parameter is 8% fluoroboric acid, the voltage is 25 V, the current is 1 A, and the film coating time is 44 s. The ImageProPlus software (6.0) calculates the grain size according to the equivalent area method. To ensure the accuracy of statistical results, at least 100 grains were counted.
In order to verify the microalloying effect of the refined samples, the grain-refined samples were aged directly at 350 °C or solutionized at 620 °C for 20 h and then aged at 350 °C. The HXD-1000TM/LCD digital display Vickers hardness tester produced by Shanghai BaoLeng company in Shanghai, China tests the hardness of samples. In order to ensure the accuracy of the test results, the average value of 7 values was taken, the load was 50 gf, and the load holding time was 10 s. The microstructure observation of the master alloy was carried out on the Quanta650 scanning electron microscope produced by the FEI Company (Hillsboro, OR, USA).

3. Results and Discussion

3.1. Phase Composition and Refining Effect of Al-5Er-0.5Ti

The XRD results for the Al-5Er and Al-5Er-0.5Ti master alloy are shown in Figure 1a. Comparing the diffraction angle, lattice constant, and crystal structure on the PDF card, one can find that the phase of the Al-5Er master alloy includes α-Al and the Al3Er with an L12 structure, as shown in Figure 1a. The phase of the Al-5Er-0.5Ti master alloy not only contains α-Al and Al3Er but also FCC-structured Ti2Al20Er. Scanning electron microscopy results for the microstructure of Al-Er(-Ti) master alloys are shown in Figure 1b,c. The primary Al3Er phase forms a eutectic structure with α-Al and distributes along the grain boundary in the Al-5Er alloy, as shown in Figure 1b. The Al3Er in the Al-5Er-0.5Ti master alloy is still distributed along the grain boundary as a eutectic structure, as shown in Figure 1c. In addition, there are Ti2Al20Er phases with block morphology, which are distributed along the grain boundary or exist in the grain interior. This kind of block phase is also found in the Al-Ti-C master alloy with the addition of Re elements [27].
The macro morphology and grain size of pure aluminum refined by Al-5Er and the Al-5Er-0.5Ti master alloy are shown in Figure 2. The master alloys are added proportionally, and the addition amount of Er and Ti in the refined samples is controlled to be 0.1 wt% and 0.01 wt%, respectively. Without the addition of master alloys, pure aluminum is composed of columnar and equiaxed crystals with an average grain size of 14,000 μm, as shown in Figure 2c. After adding the master alloy, the grain structure remains unchanged, and the grain size decreases significantly. With the addition of the Al-5Er master alloy, the grain size decreases gradually with the extension of the holding time, and the minimum size is 3300 μm at 240 min. With the addition of the Al-5Er-0.5Ti master alloy, the grain size also decreases with the extension of the holding time as shown in Figure 2d, and the minimum grain size is 720 μm after holding for 240 min. The refining effect is improved by 79.4% compared to the Al-5Er alloy.

3.2. Phase Composition and Refining Effect of Al-5Er-Ti Phase with Different Ti Contents

The XRD patterns of Al-5Er-Ti master alloys with different Ti contents are shown in Figure 3a. The phase composition of the Al-5Er-1.0Ti master alloy is similar to that of Al-5Er-0.5Ti. The main primary phases include Al3Er and Ti2Al20Er. When the Ti content was increased to 1.5, the phase composition is different from that of the master alloy with lower Ti. In addition to the Al3Er and Ti2Al20Er phases, an obvious Al3Ti phase can also be distinguished from the corresponding XRD spectrum. This confirmed that when the Er/Ti atomic ratio was different, the Ti-containing phase was also different. When the Er/Ti atomic ratio is 2.7, only Ti2Al20Er is present in the Al-Er-Ti master alloy. In the alloy with an Er/Ti atomic ratio of 1.3, Ti2Al20Er and Al3Ti coexist, which can also be verified by SEM observation as shown in Figure 3c. One can find that there are strip-shaped Al3Ti phases in addition to the eutectic Al3Er and blocky Ti2Al20Er phases. In the Al-Ti master alloy, only strip-shaped Al3Ti phases exist, as shown in Figure 3c. The length and width of the Al3Ti in the Al-5Er-1.5Ti master alloy decrease from 14.1 μm and 3.0 μm to 9.5 μm and 0.9 μm, respectively, relative to that in Al-1.5Ti. The addition of Er and Ti can not only change the size of Al3Ti but also combine with Al to form a new massive phase Ti2Al20Er with a size of 6.0 μm.
In order to prove the effect of Ti2Al20Er on grain refinement, the grain refinement effects of the Al-5Er-1.5Ti master alloy and that of the composite addition of Al-ER and Al-Ti master alloys were compared. The composition of Er and Ti in the refined samples formed by different adding methods is the same. The macro morphology refined by Al-5Er-1.5Ti, Al-1.5Ti, and mixed addition of Al-5Er/Al-1.5Ti and the grain size of the Al as a function of the holding time are shown in Figure 4. With the addition of the Al-1.5Ti master alloy, the grain size of pure aluminum reaches the minimum size of 470 μm with the extension of the holding time to 120 min. The grain size distribution in Al-Ti master alloy-refined samples are inhomogeneous, and there exist a small number of coarse equiaxial grains, as shown in Figure 4a. Compared with Figure 2a, the refining effect of Al3Ti is much better than that of Al3Er for the same atomic percent of addition, which is attributed to the better lattice matching of Al3Ti with the Al matrix [10]. When Al-5Er and Al-1.5Ti were composite added, the change law of grain size with the holding time was similar to that of Al-1.5Ti. The optimum refinement effect appeared at a holding time of 120 min, and the grain size was 440 μm. Moreover, the grain size distribution in Al-Ti and Al-Er master alloy-refined samples are homogeneous. After the refinement by the Al-5Er-1.5Ti master alloy, the minimum grain size is 300 μm at the holding time of 60 min. The refinement effect is significantly better than that of other master alloys. This indicates that the Al-5Er-1.5Ti master alloy prepared by the compound addition of Er and Ti has a better refining effect, mainly due to the existence of Ti2Al20Er.

3.3. Effect of Cooling Rate on Microstructure and Refinement Effect of Al-5Er-1.5Ti Master Alloy

The results of SEM analysis on the microstructure of the master alloy with different ingot thicknesses are shown in Figure 5. According to Figure 5, the size of Ti2Al20Er and Al3Ti in 5 mm ingots are 6.0 μm and 9.5 μm, respectively. As the ingot thickness increases, the size of the primary phase in the 12 mm ingot increases. With the continuous increase in ingot thickness, the primary phase grows further: for Al3Ti, the size is 19.3 μm and for Ti2Al20Er it is 21.7 μm in the master alloy with a 22 mm ingot thickness. This shows that with an increase in the cooling rate, the growth time of the primary phase decreases, and the size of the primary phase decreases gradually.
The grain refinement effect of the Al-5Er-1.5Ti master alloy with different ingot thicknesses was experimentally verified, and the results are shown in Figure 5f. After the pure aluminum was refined by the master alloy with a 5 mm ingot, the smallest grain size of the pure aluminum was 300 μm at a holding time of 60 min. After increasing the holding time to 240 min, the grain size increased to 350 μm. With increasing ingot thickness, the grain size variation with time is similar to that of a 5 mm ingot. After the addition of the master alloy to the 12 mm ingot, the grain size is 340 μm at a holding time of 60 min. The thickness of the ingot increased to 22 mm, and the grain size increased to 370 μm. It shows that reducing the ingot thickness and the primary phase size can improve the grain refinement effect.

3.4. Refinement Mechanism

In order to verify whether the refining effect comes from the primary phase or solute atom, an experiment was designed to dissolve the primary phase at a high temperature. First, 750 g of high-purity aluminum is melted at 955 °C. Then, a 5 mm-thick Al-5Er-1.5Ti master alloy is added to the aluminum melt, with the Er content controlled to 0.1 and the Ti content to 0.03. Finally, the aluminum melt temperature was lowered to 805 °C and 705 °C, respectively, and the refined samples were cast, and the grain size of the samples with different interval times were characterized, as shown in Figure 6. The grain size of the sample cast at 805 °C is larger than that of the sample cast at 705 °C. After high-temperature treatment at 955 °C, the grain size of the sample cast at 705 °C is significantly larger than that of the samples without high-temperature treatment, as shown in Figure 4c. Because Al3Er, Al3Ti, and Ti2Al20Er are completely dissolved into pure aluminum after high-temperature treatment at 955 °C, Er and Ti exist as solute atoms. Er’s growth limiting factor QEr is 0.09, and QTi is 6.6 [28]. The contribution of solute atoms to grain refinement is limited. The grain size of the sample cast at 705 °C is less than that at 805 °C due to the low casting temperature. Al3Ti has been recognized as capable of achieving heterogeneous nucleation through good lattice matching [10]. To evaluate the nucleation ability of Ti2Al20Er, the crystal matching between Ti2Al20Er and α-Al was studied using the E2E model [10]. The E2E model is based on the phase crystal structure, lattice constant, close arrangement surface and close arrangement direction of the close arrangement surface between the two phases. The mismatch degree of matching orientation is calculated to determine whether the mismatch degree of atomic spacing and crystal plane spacing are 10% and 6%, respectively.
Ti2Al20Er is a face-centered cubic structure, and the lattice constant is 1.4662 nm. There are three groups of closely packed crystal faces, (531), (533), and (620). The closely packed crystal direction on the (531) crystal face is <620>. The closely packed crystal direction on the (533) crystal face is <011>. The closely packed crystal direction on the (620) crystal face is <260>.The atomic arrangement of the different closely packed crystal faces of Ti2Al20Er is shown in Figure 7. The same exponential orientation is arranged differently and distinguished by a and b superscripts. Although the atomic arrangement of the closely packed crystal direction deviates from the straight line, the average atomic spacing is still calculated according to the straight line arrangement.
Al is a face-centered cubic structure, and the lattice constant is 0.4049 nm. The closely packed crystal faces (111) and (220) both contain <011> and <112>, and the closely packed crystal face (200) contains only <011>. The calculation results of the mismatch degree are shown in Table 2 and Table 3. There are three groups of orientations conforming to the E2E model. Among them, the mismatch degree of (620)Ti2Al20Er<260>Ti2Al20Er//(111)Al<110>Al is the smallest, less than 1.6%.

3.5. Microalloying

The microalloying effect of pure aluminum refined by the Al-5Er-1.5Ti master alloy was verified by an experiment. The grain-refined pure aluminum samples with a holding time of 60 min were subjected to a direct aging treatment or first a solid solution and then an aging treatment. The results of the hardness variation with aging time were shown in Figure 8. According to Figure 8a, the hardness value of the sample after direct aging treatment basically remained unchanged with the extension of aging time. After solution treatment at 620 °C for 20 h, the hardness of the samples decreased from 30.5 HV to 27.6 HV. After aging treatment at 350 °C, the hardness changed significantly, and the hardness reached the peak in 15 min, and the increase rate was 41.3%. During the solution treatment, the Al3Er phase dissolved and precipitated with hardening during the ageing treatment [29], which indicates that the Al-Er-Ti master alloy can be used for microalloying element addition, at the same time with a grain refinement effect.

4. Conclusions

In this work, methods such as refining experiments, microhardness tests, optical microscopy (OM), scanning electron microscopy (SEM), and X-Ray diffraction (XRD) were adopted to analyze the phase structure, grain refinement, and microalloying effect of the Al-5Er-Ti master alloy. The following conclusions can be drawn:
  • When the Er/Ti atomic ratio is 2.7, only Ti2Al20Er is present in the Al-5Er-Ti master alloy, and when the Er/Ti atomic ratio is reduced to 1.3, Ti2Al20Er and Al3Ti coexist;
  • Compared with Al-5Er, the refinement effect of Al-5Er-0.5Ti was better, and the results came from the Ti2Al20Er phase, and the refinement was increased by 79.4%. Compared with mixed Al-5Er and Al-1.5Ti master alloy addition methods, the Al-5Er-1.5Ti master alloy has a better refining effect of pure aluminum grains, which is derived from the Ti2Al20Er phase and Al3Ti phase;
  • There are three crystal orientations of Ti2Al20Er and α-Al that satisfy the E2E model, among which (620)Ti2Al20Er<260>Ti2Al20Er//(111)Al<110>Al is the least mismatched one;
  • The pure aluminum refined by the Al-5Er-1.5Ti master alloy has no precipitation strengthening effect after direct aging treatment. After the solution and aging treatment, the precipitation strengthening effect appeared, and the hardness reached the peak in 15 min, and the hardness increased by 41.3%.

Author Contributions

Conceptualization, J.M., Z.L., S.W., W.W., H.H. and Z.N.; Methodology, J.M., Z.L. and G.Y.; Validation, J.M., Z.L., S.W. and G.Y.; Investigation, J.M., Z.L., G.Y. and W.W.; Resources, S.W., H.H. and Z.N.; Data curation, J.M., Z.L. and G.Y.; Writing—original draft, J.M., Z.L. and G.Y.; Writing—review and editing, J.M., S.W. and W.W.; Supervision, S.W., H.H. and Z.N.; Funding acquisition, H.H. and Z.N. All authors have read and agreed to the published version of the manuscript.

Funding

This study is supported by the National Key Research and Development Program of China (2021YFB3700902, 2021YFB3704204 and 2021YFB3704205), Beijing Natural Science Foundation (2202009), National Natural Science Foundation of China (51621003), Basic Research Program of Jiangsu Province (NSF) (BK20191148), Beijing Lab Project for Modern Transportation Metallic Materials and Processing Technology, and Jiangsu Key Laboratory for Clad Materials (BM2014006).This research received no external funding.

Data Availability Statement

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

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. XRD and SEM microstructure of Al-5Er and Al-5Er-0.5Ti master alloy: (a) XRD; (b) SEM microstructure of Al-5Er; (c) SEM microstructure of Al-5Er-0.5Ti.
Figure 1. XRD and SEM microstructure of Al-5Er and Al-5Er-0.5Ti master alloy: (a) XRD; (b) SEM microstructure of Al-5Er; (c) SEM microstructure of Al-5Er-0.5Ti.
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Figure 2. The macroscopic morphology and grain size change curve of pure Al refined by the master alloy: (a) added Al-5Er; (b) added Al-5Er-0.5Ti; (c) without master alloy addition; (d) the grain size of the Al as a function of the holding time.
Figure 2. The macroscopic morphology and grain size change curve of pure Al refined by the master alloy: (a) added Al-5Er; (b) added Al-5Er-0.5Ti; (c) without master alloy addition; (d) the grain size of the Al as a function of the holding time.
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Figure 3. XRD and SEM microstructure of Al-vr-Ti and Al-Ti master alloys: (a) XRD; (b) SEM microstructure of Al-5Er-1.5Ti; (c) SEM microstructure of Al-1.5Ti.
Figure 3. XRD and SEM microstructure of Al-vr-Ti and Al-Ti master alloys: (a) XRD; (b) SEM microstructure of Al-5Er-1.5Ti; (c) SEM microstructure of Al-1.5Ti.
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Figure 4. The morphology and grain size change curves of pure aluminum refined by the Al-5Er(-1.5Ti) master alloy: (a) added Al-1.5Ti; (b) added Al-5Er/Al-1.5Ti; (c) added Al-5Er-1.5Ti; (d) the grain size of the Al as a function of the holding time.
Figure 4. The morphology and grain size change curves of pure aluminum refined by the Al-5Er(-1.5Ti) master alloy: (a) added Al-1.5Ti; (b) added Al-5Er/Al-1.5Ti; (c) added Al-5Er-1.5Ti; (d) the grain size of the Al as a function of the holding time.
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Figure 5. Microstructure and grain refinement effect of Al-5Er-1.5Ti master alloy with different ingot thicknesses: (a) microstructure of 5 mm ingot thickness; (b) microstructure of 12 mm ingot thickness; (c) microstructure of 22 mm ingot thickness; (d) size of Ti2Al20Er with different ingot thicknesses; (e) size of Al3Ti with different ingot thicknesses; (f) refined grain size with different holding times for Al-5Er-1.5Ti master alloy with different ingot thicknesses.
Figure 5. Microstructure and grain refinement effect of Al-5Er-1.5Ti master alloy with different ingot thicknesses: (a) microstructure of 5 mm ingot thickness; (b) microstructure of 12 mm ingot thickness; (c) microstructure of 22 mm ingot thickness; (d) size of Ti2Al20Er with different ingot thicknesses; (e) size of Al3Ti with different ingot thicknesses; (f) refined grain size with different holding times for Al-5Er-1.5Ti master alloy with different ingot thicknesses.
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Figure 6. The grain sizes of pure Al refined by the Al-5Er-1.5Ti master alloy with a high-temperature treatment.
Figure 6. The grain sizes of pure Al refined by the Al-5Er-1.5Ti master alloy with a high-temperature treatment.
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Figure 7. Atomic arrangement of phase Ti2Al20Er:(a) (531); (b) (533); (c) (620).
Figure 7. Atomic arrangement of phase Ti2Al20Er:(a) (531); (b) (533); (c) (620).
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Figure 8. Hardness curves of the refined aluminum after different heat treatments: (a) direct aging at 350 °C; (b) 620 °C × 20 h + 350 °C.
Figure 8. Hardness curves of the refined aluminum after different heat treatments: (a) direct aging at 350 °C; (b) 620 °C × 20 h + 350 °C.
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Table 1. Chemical composition of the master alloy.
Table 1. Chemical composition of the master alloy.
AlloysElements
Er (wt%)/(at%)Ti (wt%)/(at%)Al
Al-5Er5.20/0.88/Bal.
Al-1.5Ti/1.45/0.82Bal.
Al-5Er-0.5Ti5.1/0.860.49/0.28Bal.
Al-5Er-1.0Ti5.1/0.860.98/0.55Bal.
Al-5Er-1.5Ti5.3/0.901.43/0.81Bal.
Table 2. Interplanar spacing mismatching (relative to Al) between closely packed or nearly closely packed planes in Ti2Al20Er (a = 1.4662 nm) and Al matrix (a = 0.4049 nm) (%).
Table 2. Interplanar spacing mismatching (relative to Al) between closely packed or nearly closely packed planes in Ti2Al20Er (a = 1.4662 nm) and Al matrix (a = 0.4049 nm) (%).
(531)//
(111)
(531)//
(200)
(531)//
(220)
(533)//
(111)
(533)//
(200)
(533)//
(220)
(620)//
(111)
620)//
(200)
(620)//
(220)
−5.99−22.43−73.174.41−10.42−56.180.86−14.53−61.98
Table 3. Interatomic spacing mismatching (relative to Al) along possible matching directions between Ti2Al20Er (a = 1.4662 nm) and Al matrix (a = 0.4049 nm) (%).
Table 3. Interatomic spacing mismatching (relative to Al) along possible matching directions between Ti2Al20Er (a = 1.4662 nm) and Al matrix (a = 0.4049 nm) (%).
<620> a//<110><620> b//(110)<011> a//(112)<011> b//(112)<260> a//(110)<260> b//(110)
4.895.00−9.39−4.541.511.31
a, b are used to distinguish different crystal planes within the same crystal family.
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MDPI and ACS Style

Ma, J.; Lei, Z.; Wen, S.; Yang, G.; Wei, W.; Huang, H.; Nie, Z. Al-5Er-Ti Master Alloy with Both Grain Refinement and Microalloying Effects. Metals 2025, 15, 43. https://doi.org/10.3390/met15010043

AMA Style

Ma J, Lei Z, Wen S, Yang G, Wei W, Huang H, Nie Z. Al-5Er-Ti Master Alloy with Both Grain Refinement and Microalloying Effects. Metals. 2025; 15(1):43. https://doi.org/10.3390/met15010043

Chicago/Turabian Style

Ma, Jingrui, Zhiguo Lei, Shengping Wen, Guang Yang, Wu Wei, Hui Huang, and Zuoren Nie. 2025. "Al-5Er-Ti Master Alloy with Both Grain Refinement and Microalloying Effects" Metals 15, no. 1: 43. https://doi.org/10.3390/met15010043

APA Style

Ma, J., Lei, Z., Wen, S., Yang, G., Wei, W., Huang, H., & Nie, Z. (2025). Al-5Er-Ti Master Alloy with Both Grain Refinement and Microalloying Effects. Metals, 15(1), 43. https://doi.org/10.3390/met15010043

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