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Article

Effects of Adding Active Elements to Aluminum-Based Filler Alloys on the Bonding of 6061 Aluminum Alloy and Alumina

by
Yu-Kai Sun
1,
Shih-Ying Chang
2,*,
Lung-Chuan Tsao
3,
Tung-Han Chuang
1,
Guo-Zhan Zhang
2 and
Chih-Yi Yeh
2
1
Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan
2
Department of Mechanical Engineering, National Yunlin University of Science & Technology, Yunlin 64002, Taiwan
3
Department of Materials Engineering, National Pingtung University of Science & Technology, Pingtung 91201, Taiwan
*
Author to whom correspondence should be addressed.
Appl. Sci. 2021, 11(21), 10440; https://doi.org/10.3390/app112110440
Submission received: 11 October 2021 / Revised: 2 November 2021 / Accepted: 4 November 2021 / Published: 6 November 2021
(This article belongs to the Section Materials Science and Engineering)
Browse Figures
Versions Notes

Abstract

:
In this study, AA6061/AA6061 and AA6061/alumina were directly brazed with Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys at 530 °C for 10 min without the use of flux. The addition of titanium and rare-earth elements into Al10.8Si10Cu alloy effectively improved the bonding shear strengths of AA6061/AA6061 and AA6061/alumina joints. The highest joint shear strengths were 61.1 and 19.2 MPa, respectively. The Al10.8Si10Cu filler alloy without titanium and rare-earth elements could not wet on the alumina and caused failure of the AA6061/alumina joint. The shear strengths of the AA6061/AA6061 and AA6061/alumina joints both strongly depended on the active element addition. Due to the high chemical activity of the rare-earth elements, they formed AlLa between the Al10Si10Cu4Ti0.1RE filler alloy and alumina. The addition of rare-earth elements into Al10Si10Cu4Ti filler alloy resulted in significant enhancement of the average bond strength of AA6061/alumina joints, from 8.0 to 14.8 MPa.

1. Introduction

The joining of alumina to aluminum alloy is widely used in electronic devices, chemical equipment and biomedicine [1,2,3]. In recent years, several bonding methods for joining metal with ceramic have been developed [4,5]. Among the variety of joining technologies, active brazing is an excellent method of joining metal with ceramic [6,7]. Ag-Cu-Ti alloys are adopted as highly reliable filler metals for ceramic/metal brazing [8,9,10]. However, the bonding temperature is above 850 °C, which is too high relative to the aluminum alloys. Therefore, it is necessary to design filler alloys with low melting points for joining aluminum alloy and ceramic. Active low-melting-point filler alloys such as Sn-, In- and Zn-based filler alloys with elements having high chemical activity, such as titanium, magnesium and rare-earth elements (RE), have been developed in the past few years [11,12,13,14,15,16]. Due to the low mechanical properties at high temperature, the Sn- and In-based filler metals are limited for high-temperature application. Zn-based filler metals with higher melting points can be used at temperatures below about 350 °C. However, zinc is prone to oxidation and causes problems with wettability and corrosion. In addition, Zn-based filler metals are not acceptable in many high-vacuum and high-temperature applications due to the high vapor pressure of zinc. The Al12Si eutectic alloy has been adopted as a reliable filler alloy for aluminum alloy brazing [17]. However, the brazing temperature is about 600 °C, which is too high relative to the solidus temperature of many aluminum alloys. Thus, it is necessary to design low-melting-point aluminum filler alloys. The general trend is that the addition of copper, zinc, magnesium and germanium into the eutectic Al12Si filler alloy lowers the brazing temperature [18,19,20]. In a series of investigations [18,19,21,22], the Al-Si-Cu alloy was considered a possible choice as a filler metal for aluminum alloy brazing. Brazing of metal with ceramic using low-melting-point aluminum-based filler alloys is still a challenge. This study employed active Al-Si-Cu-Ti-RE filler metals to join aluminum alloys with alumina. Most rare-earth elements have similar atomic radii and chemical properties. The solvent extraction processes for selective separation and purification into a single rare-earth element are complicated and costly. Mixed rare-earth elements contain the characteristics of different rare-earth elements. Zhao et al. [23] pointed out that the Sn-Zn-Cu solders with mixed rare-earth elements exhibited better solderability than the single rare-earth element-containing solders. Therefore, mixed rare-earth elements were chosen as the additional active elements in this study. The effects of the additions of active elements, namely, titanium and trace mixed rare-earth elements, into Al-Si-Cu filler alloys on the joint strength and interfacial reaction were investigated.

2. Experimental

The Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys used in the study were prepared by melting 99.99% purity copper and titanium slugs, mixed rare-earth elements and the master alloy of Al-12 wt.% Si (supplied by Degussa AG, Hanau, Germany) in an electric arc furnace under a high-purity inert atmosphere. The rare-earth elements used in the study were mixed rare-earth elements. The chemical composition was 77.82 wt.% lanthanum, 16.84 wt.% praseodymium, 3.24 wt.% cerium and 2.10 wt.% neodymium. The chemical composition of the filler alloys used in the study is shown in Table 1. To ensure a homogeneous composition within the filler alloys, the melt was stirred by manual operation for 10 min. The filler alloys were solidified in a mold with an internal diameter of 20 mm under water cooling, and the cast ingots were rolled to a thickness of 300 μm. Prior to microstructural observations, the three filler alloys were metallographically ground and polished. The microstructures were observed with a field emission scanning electron microscope (FE-SEM, JEOL JSM-6700F). The chemical composition was analyzed by energy dispersive X-ray analysis (EDX). The existing phases of the filler alloys were identified with an X-ray diffractometer (Rigakue ATX-E) with Cu Kα radiation (λ = 1.54 Å) and a scanning rate of 1.8°/min. The thermal properties of the Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu0.1RE filler alloys were determined by differential thermal analysis (DTA, TA Instruments SDT-2960) at a heating rate of 10 °C/min from ambient to 700 °C under a high-purity inert atmosphere.
The aluminum alloy joined in this study was in the form of 2 mm thick AA6061 aluminum plates, with dimensions of 40 × 10 × 2 mm. The chemical composition of AA6061 is provided in Table 2. Bulk alumina ceramic with dimensions of 7 × 7 × 4 mm was fabricated by pressure casting. After 24 h of drying at 60 °C, the alumina was sintered at 1600 °C for 2 h. A lap joint configuration was used to evaluate the bonding strength. The geometry and dimensions of the AA6061/AA6061 and AA6061/alumina joints subjected to shear testing are demonstrated in Figure 1a,b, respectively.
Prior to joining, the bonding surfaces of AA6061 and the surfaces of the filler alloys were ground with 1200-grit silicon carbide paper and then cleaned in acetone. Copper and aluminum have high vapor pressure at the bonding temperature in order to prevent the evaporation of the elements during the bonding process. Therefore, the argon partial pressure is introduced into a vacuum furnace during the bonding process. The brazing process was conducted with a heating rate of 10 °C/min in a vacuum furnace under a high-purity Ar gas atmosphere at 530 °C for 10 min. For the metallographic study of the bonding interfaces, the joined specimens were cross-sectioned. In order to avoid damage to the joints caused by metallographic production, after the completion of the bonding, a set of test specimens was hot-embedded, and then was cut with a precision low-speed diamond saw for further grinding and polishing with SiC paper and diamond paste, respectively. The microstructures of the bonding interfaces were characterized with a field emission scanning electron microscope (FE-SEM) and energy dispersive X-ray (EDX). The microhardness of the filler alloys and the joint interfaces was measured with a micro-sclerometer (Shimadzu HMV-2), using a 20 gf indenting load and a dwell time of 10 s. The shear strengths of the joints were determined with a tensile testing machine (Hung-Ta HT-2102) at room temperature. To ensure the accuracy of the results, five measurements of joint strength were performed for each brazing condition and the average was calculated. The fractographs of the brazed joints after the shear tests were characterized with a FE-SEM coupled to an EDX.

3. Results and Discussion

Micrographs of the as-solidified Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys are shown in Figure 2a–c, respectively. According to the EDX results, the compositions of the phase (light) at Spot 1 in Figure 2a, Spot 5 in Figure 2b and Spot 10 in Figure 2c, were Al:Cu = 69.7:30.3 (at.%), Al:Cu = 64.0:36.0 (at.%) and Al:Cu = 65.1:34.9 (at.%) respectively, which corresponded to the Al2Cu phase. According to the results of EDX analysis, the Al-Si binary phase diagram [24] and the Al-Si-Cu ternary phase diagram [25], Spot 2, Spot 4 and Spot 11 in Figure 2a–c respectively, show a gray particle containing a high amount of Si, which can be interpreted as Si-rich solid solution particles. Spot 3, Spot 6 and Spot 8 in Figure 2a–c respectively, can be inferred as the α-Al solid solution phase. The chemical compositions of the phases (gray) at Spot 7 in Figure 2b and Spot 9 in Figure 2c were identified by EDX as Al:Si:Ti = 14.8:55.0:30.2 (at.%) and Al:Si:Ti = 14.6:55.7:29.7 (at.%) respectively, which corresponded to the Al5Si12Ti7 intermetallic compound [26]. The EDX analysis results of the filler alloys are listed in Table 3.
The X-ray diffraction patterns for the Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys are presented in Figure 3. The X-ray diffraction was carried out in the presence of the Al2Cu intermetallic compound and the Si-rich and Al-rich alloy of the as-solidified filler metals. Both X-ray diffraction analysis and SEM-EDX observation confirmed the presence of the Al5Si12Ti7 intermetallic compound in the Al10Si10Cu4Ti and Al10Si10Cu0.1RE filler alloys.
Figure 4 shows the DTA curves of the Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler metals. A prior study [19] indicated that the liquidus and solidus temperatures of the Al12Si alloy were 586.1 and 591.7 °C, respectively. The addition of 10 wt.% copper into the Al12Si filler alloy formed the Al10.8Si10Cu alloy and lowered the solidus and liquidus temperatures to 522.25 and 569.99 °C, respectively [19]. The first exothermic peak of the Al10.8Si10Cu filler metal at 527.72 °C was attributed to the reaction of θ(Al2Cu) + Si + α(Al)→L. The second exothermic peak at 569.99 °C was related to melting of the Al-Si eutectic. When 4 wt.% Ti was added into the Al-Si-Cu filler alloys, the solidus and liquidus temperatures were reduced, and the Al-Si eutectic melting reaction was inhibited. As a result, a low-melting-point alloy reaction was initiated, and only one exothermic peak appeared for the Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler metals.
Figure 5a–c respectively present the microstructures under BSE mode of the AA6061 joints with Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys after brazing at 530 °C for 10 min. Some Si-rich phase particles and a large number of Al2Cu precipitates were found at grain boundaries in the Al10.8Si10Cu filler alloy. The Al2Cu particles were smaller in the titanium-containing Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys than in the Al10.8Si10Cu filler alloy. Only a very few tiny AlLa intermetallic compound particles with a size of 2–10 μm have been found in the Al10Si10Cu4Ti0.1RE filler alloy [27,28]. The addition amount of mixed rare-earth elements is very small, only 0.1 wt.%. Thus, except for the AlLa phase, another trace rare-earth element phase cannot be observed by SEM. In the study of Chen et al. [28], the slender grains of the AlLa intermetallic compounds with a size of about 5–15 μm can be found in the A356 aluminum alloy with 0.3% La and 0.2% Yb mixed rare-earth elements. Moreover, Samuel et al. [27] studied the metallography of rare-earth intermetallic compounds in the rare-earth element-containing Al-Cu-Mg and Al-Si-Cu-Mg alloys. The strip grains of aluminum-rare-earth intermetallic compounds with a size of 15–20 μm can be determined by SEM and EDX. According to the composition analysis of EDX and the studies of rare-earth elements containing aluminum alloys by Chen et al. [28] and Samuel et al. [27], it is believed that there are AlLa intermetallic compounds in the Al10Si10Cu4Ti0.1RE filler alloy.
The average joint shear strengths of the AA6061/AA6061 joints bonded with Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys were determined to be 39.8, 47.8 and 57.3 MPa. The highest joint shear strengths were 46.54, 51.5 and 61.1 MPa, respectively. The shear strengths of the joints increased significantly with the addition of active elements, as shown in Figure 6. Aluminum alloys are prone to form a dense oxide layer on the surface that hinders the reaction of aluminum alloy with the filler alloy. In order to obtain a good joint, a highly corrosive specially formulated flux is necessary to be used. Niu et al. [20] used Al-Si-Ge, Al-Si-Zn and Al-Si-Ge-Zn filler metal with AlF3-KF-KCl-CsF flux to join 6061 aluminum alloys at higher joining temperature (570 °C), and the joining strengths reached 87.5, 103.6 and 138.2 MPa, respectively. The flux can cause environmental pollution, and the residual flux may also cause corrosion of the joint. In the study, the flux-less joining strength with Al10Si10Cu4Ti0.1RE filler alloys (57.3 MPa) is higher than the NaOH surface-treated adhesive bonding (21.8 MPa) [29], the adhesive bonding with mechanically pretreated rough surface (34.4 MPa) [30] and gas metal arc welding (53.3 MPa) [31].
Figure 7 presents the microhardness profiles measured across the brazing interfacial region after bonding at 530 °C for 10 min. Due to the large number of intermetallic compounds and Si-rich particles in the filler alloys, the hardness values of the filler alloys were higher than that of the AA6061 substrate. The hardness values of the Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys were higher than that of the Al10.8Si10Cu filler alloy due to Al5Si12Ti7 precipitation hardening and Al2Cu grain refinement. Large increments of the hardness values of the Al10Si10Cu4Ti0.1RE filler alloy resulted when the trace rare-earth elements were added.
Figure 8a–c show the fractography of the AA6061/AA6061 joints brazed with Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys, respectively. All of the fractographs of the joints indicated that the fractured surfaces were covered with filler alloys with intermetallic compounds and Si-rich solid solution particles, suggesting that the fractures of the joints occurred mainly in the interior of the filler alloys. Mainly intergranular fracture occurred at the joint with Al-10.8Si-10Cu filler metal due to the coarse Al2Cu intermetallic compounds at the grain boundaries. In the joints brazed with Al10.8Si10Cu4Ti and Al10.8Si10Cu4Ti0.1RE filler alloys, mixed intergranular and transgranular fractures were found at the brazing interfaces.
Cross-sectional SEM micrographs under BSE mode of the AA6061/alumina joints brazed with Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys at 530 °C for 10 min are presented in Figure 9a–c, respectively. Satisfactory bonding interfaces formed in the AA6061 and alumina joints. No obvious defects were found at the joint interfaces. A few Si-rich and Al2Cu intermetallic compound particles were found at the interface between the Al10.8Si10Cu filler alloy and alumina, as shown in Figure 9a. Large grains were observed in the Al10Si10Cu4Ti filler metal, as were Al2Cu and Al5Si12Ti7 intermetallic compounds on the grain boundaries, as shown in Figure 9b. Compared with the Al10Si10Cu4Ti filler alloy, the Al10Si10Cu4Ti0.1RE filler alloy had a smaller grain structure, and rare-earth elements accumulated at the interface of the Al10Si10Cu4Ti0.1RE filler alloy and alumina. According to the EDX results, the composition of La segregates was 53.4 at.% of Al and 46.6 at.% of La, which corresponded to the AlLa intermetallic compound [27,28].
The joint shear strengths of the AA6061/alumina joints with Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys are shown in Figure 10. The joint with the Al10.8Si10Cu filler alloy separated at the beginning of the shear test, so the joint shear strength was not obtained. Although, the Al10.8Si10Cu filler alloy can be spread on the alumina under a small pressure during the joining process, and there is no obvious defect in the interface between Al10.8Si10Cu filler alloy and alumina. Since there is no metallurgical reaction, that results in almost no bonding strength between Al10.8Si10Cu filler alloy and alumina. The highest shear strengths of the AA6061/alumina joints with Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys were 11.7 and 19.2 MPa, respectively. The shear strength of the AA6061/alumina joint with the Al10Si10Cu4Ti0.1RE filler alloy was significantly higher than that of the joint with the Al10Si10Cu4Ti filler alloy. The average shear strengths of the AA6061/alumina joint with Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys were 8.0 and 14.8 MPa, respectively. The role of titanium in Al-Si-Cu filler is the same as the titanium-containing filler metals, such as tin-based [13,14,15], silver-based [9,10] and indium-based [11] filler alloys, which can promote the wetting of the filler on the ceramic surface and the interfacial reaction between the filler and the ceramic.
The fractography of joints brazed with Al10.8Si10Cu filler alloy after shear tests is shown in Figure 11. All the filler alloy was on the fracture surface of the AA6061 side of the joint brazed with Al10.8Si10Cu filler metal after the shear test. Many particles of Al2Cu intermetallic compounds and Si-rich phase were found on the fracture surface of the AA6061 side, and no filler alloy was observed on the alumina surface side. These results indicated that the Al10.8Si10Cu filler alloy could not form a wetting reaction on the alumina, which led to the joint having almost no strength. Fractography of the AA6061/alumina joint with the Al10Si10Cu4Ti filler alloy revealed that the brazed joint fractured along the filler metal/alumina interface, as shown in Figure 12a,b. After the shear test, most of the Al10Si10Cu4Ti filler alloy was on the AA6061 surface, and very little filler metal was observed on the alumina surface. Figure 13a,b show the fractography of an AA6061/alumina joint with Al10Si10Cu4Ti0.1RE filler alloy after shear test. Both of the fractured surfaces of the AA6061 and alumina were covered with Al10Si10Cu4Ti0.1RE filler alloy. Since more residual attached filler alloy was observed on the alumina surface of the AA6061/alumina joint brazed with Al10Si10Cu4Ti0.1RE filler alloy than on the joint brazed with Al10Si10Cu4Ti alloy, high AA6061/alumina joint strength was achieved by brazing with the Al10Si10Cu4Ti0.1RE filler alloy at 530 °C for 10 min.

4. Conclusions

The addition of 4 wt.% Ti into the Al10.8Si10Cu filler alloy decreased the solidus temperature from 522.3 to 510.5 °C and the liquidus temperature from 570.0 to 549.2 °C. The main microstructures of the Al10.8Si10Cu filler alloy consisted of Al-rich and Si-rich solid solution phases and Al2Cu intermetallic compounds. The Al10Si10Cu4Ti and Al10Si10Cu0.1RE filler alloys contained Al-rich and Si-rich solid solution phases and Al2Cu and Al5Si12Ti7 intermetallic compounds. The Ti addition in the Al10.8Si10Cu filler alloys reduced the Al2Cu particle size. AlLa intermetallic compounds formed in the Al10Si10Cu4Ti0.1RE filler metal. Due to the large number of intermetallic compounds and Si-rich particles in the filler alloys, the hardness values of all the filler alloys were higher than that of the AA6061 substrate. The Ti addition in the Al10.8Si10Cu filler alloys increased the hardness due to Al5Si12Ti7 precipitation hardening and Al2Cu grain refinement. When the trace rare-earth elements were added to the Al10.8Si10Cu4Ti filler alloy, the hardness values increased further. The average joint shear strengths of the AA6061/AA6061 joints bonded with the Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys were determined to be 39.8, 47.8 and 57.3 MPa, and the highest joint shear strengths were 46.5, 51.5 and 61.1 MPa, respectively. The Al10.8Si10Cu filler alloy without titanium and rare-earth elements cannot be used to join AA6061 and alumina. The shear strength of the AA6061/alumina joint brazed with the Al10Si10Cu4Ti0.1RE filler alloy was significantly higher than that of the AA6061/alumina joint brazed with the Al10Si10Cu4Ti filler alloy. The highest shear strengths of the AA6061/alumina joints brazed with Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys were 11.7 and 19.2 MPa, respectively.

Author Contributions

Conceptualization, Y.-K.S., S.-Y.C., L.-C.T., T.-H.C. and G.-Z.Z.; Data curation, Y.-K.S., L.-C.T. and G.-Z.Z.; Investigation, Y.-K.S., S.-Y.C., L.-C.T., G.-Z.Z. and C.-Y.Y.; Methodology, L.-C.T. and T.-H.C.; Project administration, S.-Y.C. and T.-H.C.; Validation, Y.-K.S., S.-Y.C., G.-Z.Z. and C.-Y.Y.; Writing—original draft, Y.-K.S. and S.-Y.C.; Writing—review & editing, Y.-K.S., L.-C.T. and T.-H.C. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by Ministry of Science and Technology grant number MOST 109-2221-E-224-006.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

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Applsci 11 10440 g001 550
Figure 1. The geometry of the (a) AA6061/AA6061 and (b) AA6061/alumina joined specimens subjected to shear testing.
Figure 1. The geometry of the (a) AA6061/AA6061 and (b) AA6061/alumina joined specimens subjected to shear testing.
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Applsci 11 10440 g002 550
Figure 2. Microstructures under BSE mode of the as-solidified (a) Al10.8Si10Cu, (b) Al10Si10Cu4Ti and (c) Al10Si10Cu0.1RE filler alloys.
Figure 2. Microstructures under BSE mode of the as-solidified (a) Al10.8Si10Cu, (b) Al10Si10Cu4Ti and (c) Al10Si10Cu0.1RE filler alloys.
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Applsci 11 10440 g003 550
Figure 3. XRD analysis of the Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler metals.
Figure 3. XRD analysis of the Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler metals.
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Applsci 11 10440 g004 550
Figure 4. DTA curves of the Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys.
Figure 4. DTA curves of the Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys.
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Figure 5. The microstructures under BSE mode of the AA6061 joints with (a) Al10.8Si10Cu, (b) Al10Si10Cu4Ti and (c) Al10Si10Cu4Ti0.1RE filler alloys after brazing at 530 °C for 10 min.
Figure 5. The microstructures under BSE mode of the AA6061 joints with (a) Al10.8Si10Cu, (b) Al10Si10Cu4Ti and (c) Al10Si10Cu4Ti0.1RE filler alloys after brazing at 530 °C for 10 min.
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Applsci 11 10440 g006 550
Figure 6. The shear strengths of AA6061/AA6061 joints bonded with Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu0.1RE filler alloys.
Figure 6. The shear strengths of AA6061/AA6061 joints bonded with Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu0.1RE filler alloys.
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Figure 7. Microhardness profiles for the interfaces of AA6061/AA6061 joints brazed with Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys at 530 °C for 10 min.
Figure 7. Microhardness profiles for the interfaces of AA6061/AA6061 joints brazed with Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys at 530 °C for 10 min.
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Applsci 11 10440 g008a 550Applsci 11 10440 g008b 550
Figure 8. Fractography of the AA6061/AA6061 joints brazed with (a) Al10.8Si10Cu, (b) Al10Si10Cu4Ti and (c) Al10Si10Cu4Ti0.1RE filler alloys.
Figure 8. Fractography of the AA6061/AA6061 joints brazed with (a) Al10.8Si10Cu, (b) Al10Si10Cu4Ti and (c) Al10Si10Cu4Ti0.1RE filler alloys.
Applsci 11 10440 g008aApplsci 11 10440 g008b
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Figure 9. The microstructures under BSE mode of the AA6061/alumina joints with (a) Al10.8Si10Cu, (b) Al10Si10Cu4Ti and (c) Al10Si10Cu4Ti0.1RE filler alloys after brazing at 530 °C for 10 min.
Figure 9. The microstructures under BSE mode of the AA6061/alumina joints with (a) Al10.8Si10Cu, (b) Al10Si10Cu4Ti and (c) Al10Si10Cu4Ti0.1RE filler alloys after brazing at 530 °C for 10 min.
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Figure 10. The shear strengths of AA6061/alumina joints bonded with Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu0.1RE filler alloys.
Figure 10. The shear strengths of AA6061/alumina joints bonded with Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu0.1RE filler alloys.
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Figure 11. Fractography of the aluminum alloy/alumina joint bonded with the Al10.8Si10Cu filler alloy: (a) AA6061 side and (b) alumina side.
Figure 11. Fractography of the aluminum alloy/alumina joint bonded with the Al10.8Si10Cu filler alloy: (a) AA6061 side and (b) alumina side.
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Applsci 11 10440 g012a 550Applsci 11 10440 g012b 550
Figure 12. Fractography of the aluminum alloy/alumina joint bonded with the Al10Si10Cu4Ti filler alloy: (a) AA6061 side and (b) alumina side.
Figure 12. Fractography of the aluminum alloy/alumina joint bonded with the Al10Si10Cu4Ti filler alloy: (a) AA6061 side and (b) alumina side.
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Figure 13. Fractography of the aluminum alloy/alumina joint bonded with the Al10Si10Cu4Ti0.1RE filler alloy: (a) AA6061 side and (b) alumina side.
Figure 13. Fractography of the aluminum alloy/alumina joint bonded with the Al10Si10Cu4Ti0.1RE filler alloy: (a) AA6061 side and (b) alumina side.
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Table
Table 1. The chemical composition of the filler alloys used in the study (wt.%).
Table 1. The chemical composition of the filler alloys used in the study (wt.%).
Filler AlloyAlSiCuTiLaPrCeNe
Al10.8Si10CuBal.10.810.0---------------
Al10Si10Cu4TiBal.10.010.04.0------------
Al10Si10Cu4Ti0.1REBal.10.010.04.00.0780.0170.0030.002
Table
Table 2. The chemical composition of AA6061 (wt.%).
Table 2. The chemical composition of AA6061 (wt.%).
AlSiCrCuFeMgMnTiZn
Bal.0.650.170.240.390.910.310.010.04
Table
Table 3. The EDX analysis results of the filler alloys (at.%).
Table 3. The EDX analysis results of the filler alloys (at.%).
SpotAlSiCuTiPossible Phase
166.3---33.7---Al2Cu
21.898.2------Si-rich
397.51.70.8---Al-rich
40.799.3------Si-rich
564.0---36.0---Al2Cu
698.31.00.7---Al-rich
714.855.0---30.2Al5Si12Ti7
898.21.30.5---Al-rich
914.655.7---29.7Al5Si12Ti7
1065.1---34.9---Al2Cu
111.198.9------Si-rich
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Sun, Y.-K.; Chang, S.-Y.; Tsao, L.-C.; Chuang, T.-H.; Zhang, G.-Z.; Yeh, C.-Y. Effects of Adding Active Elements to Aluminum-Based Filler Alloys on the Bonding of 6061 Aluminum Alloy and Alumina. Appl. Sci. 2021, 11, 10440. https://doi.org/10.3390/app112110440

AMA Style

Sun Y-K, Chang S-Y, Tsao L-C, Chuang T-H, Zhang G-Z, Yeh C-Y. Effects of Adding Active Elements to Aluminum-Based Filler Alloys on the Bonding of 6061 Aluminum Alloy and Alumina. Applied Sciences. 2021; 11(21):10440. https://doi.org/10.3390/app112110440

Chicago/Turabian Style

Sun, Yu-Kai, Shih-Ying Chang, Lung-Chuan Tsao, Tung-Han Chuang, Guo-Zhan Zhang, and Chih-Yi Yeh. 2021. "Effects of Adding Active Elements to Aluminum-Based Filler Alloys on the Bonding of 6061 Aluminum Alloy and Alumina" Applied Sciences 11, no. 21: 10440. https://doi.org/10.3390/app112110440

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