With the continuous advancement of manufacturing technologies, particularly 3D printing—specifically metal laser powder bed fusion (LPBF)—industry has gained unprecedented design freedom and manufacturing flexibility. Aluminum alloys, as lightweight materials, are widely used in aerospace, automotive, electronics, and other sectors. However, conventional aluminum alloys still face significant challenges in mechanical properties, high-temperature resistance, and ductility, which limit their application at more advanced levels.

This paper presents a recent research achievement: powder production using the rePowder ultrasonic atomization system from AMAZEMET. Through systematic design and microstructural control, an innovative aluminum alloy has been successfully developed, exhibiting high strength, excellent ductility, and superior high-temperature resistance, thereby opening new avenues for enhancing the performance of aluminum alloys in additive manufacturing.

Background

Aluminum alloys, owing to their excellent specific strength, corrosion resistance, and machinability, have become important structural materials. In particular, the aerospace and automotive industries are experiencing growing demand for lightweight, high‑strength materials. However, conventional aluminum alloys face several limitations:

• Insufficient toughness: Many high-strength aluminum alloys experience a significant reduction in toughness upon strengthening, leading to a tendency toward brittle fracture.
• Poor thermal stability: Under high-temperature conditions, the material’s performance degrades, limiting its applicability in high-temperature environments.
• Defect Sensitivity: During laser manufacturing, defects such as porosity and cracks frequently occur, compromising mechanical properties.

Accordingly, how to enhance toughness and thermal stability while maintaining strength has become a major research focus.

Innovative Breakthrough

1. The Core Concept of Microstructure Design

The research team leveraged AMAZEMET’s high-precision ultrasonic atomization system and, grounded in a deep understanding of the relationship between microstructure and material properties, employed a combined approach of digital simulation and experimental validation. By integrating chemical control with heat‑treatment techniques, they optimized the composition and distribution of the microstructural phases.

Key strategies include:

• Control the quantity and distribution of the major phases in the alloy.
• Adjust the type and size of the precipitate phase.
• Improve the grain microstructure and enhance grain boundary properties.

2. Simulation Support: From Prediction to Validation

Using computational tools such as the Scheil model, we simulated the phase transformation behavior of alloys under realistic manufacturing conditions and predicted the effects of varying elemental compositions on microstructure, thereby providing quantitative guidance for subsequent experiments.

By tuning the Zr (zirconium) and Ni (nickel) contents, an optimized phase composition was achieved, effectively enhancing the material’s ductility and toughness.

Material Design

1. Elemental Regulation: The Roles of Zr, Ni, and Er

• Zr (zirconium): Acts as a grain refiner, promoting grain refinement and inhibiting crack propagation. By adjusting the Zr content, the formation of the Al₃Zr phase can be controlled, thereby enhancing grain boundary strength.
• Ni (nickel): As a key element in the strengthening phase, it promotes the formation of precipitates and enhances high-temperature strength; however, excessive amounts may lead to increased embrittlement.
• Er (erbium): Can regulate the formation of the L1₂ phase, strengthen precipitation‑induced grain refinement, and enhance the material’s stress‑bearing capacity.

By tuning the proportions of these elements, a steady-state optimization of the microstructure was achieved.

2. Heat Treatment Control: Dynamic Optimization of Microstructure

Following laser powder bed fusion additive manufacturing, heat treatments at various temperatures and durations refine the size and distribution of precipitate phases, thereby significantly enhancing the material’s toughness and high-temperature performance.

In particular, under heat treatment at 400°C, the material’s hardness remains stable, demonstrating excellent thermal stability.

Microstructural Features: Key Influencing Factors

01 Grain Refinement

Grain refinement is key to enhancing both strength and toughness. In this study, by appropriately optimizing the alloying element ratios and heat‑treatment parameters, a uniform fine‑grained microstructure was achieved.

The finer the grains, the greater the number of grain boundaries, which inhibit crack propagation and enhance toughness.

02 Precipitate Phase Control

The microstructural distribution of precipitate phases such as Al₃Zr and Al₃Ni determines the material’s strength–toughness balance.

Size: Fine precipitates help enhance strength while preventing stress concentration.

Quantity: Appropriately control the precipitate density to balance strength and toughness.

03 Hole and Crack Suppression

In laser manufacturing, porosity and cracks are major detrimental factors that compromise material performance. The research team optimized laser processing parameters to ensure uniform heat input during solidification, thereby minimizing defects to the greatest extent possible.

Furthermore, fine grain size and uniform precipitation help to retard crack propagation.

Performance

1. Mechanical Properties

• Strength: The tensile strength reaches 279 ± 11 MPa, approximately 25% higher than that of conventional comparable alloys, while maintaining excellent fracture toughness.
• Toughness: Tensile ductility surged from less than 1% to 19%, marking a qualitative leap.
• Hardness: After heat treatment, the hardness decreases by only 15%, demonstrating excellent thermal stability.

2. Microscopic Fracture Behavior

Fracture analysis reveals that, following optimization, the fracture surface exhibits numerous ductile dimples and fine, glue-like cracks, which inhibit crack propagation and demonstrate excellent ductility.

3. High-Temperature Performance

In a high-temperature environment of 250°C, the material can still retain most of its mechanical properties, meeting practical engineering requirements.

Optimization of Laser Manufacturing Processes

Precise control of laser processing parameters is essential for ensuring the optimization of microstructures. In this study, the following were employed:

• Laser energy density: Optimize laser power and scanning speed to ensure sufficient melting while avoiding overheating.
• Scanning strategy: An interleaved scanning path is employed to minimize residual stress and porosity.
• Subsequent heat treatment: The system precisely controls the temperature and duration of the heat treatment, finely tuning the precipitate phases and grain structure.

Through these measures, the fabricated prototypes achieved the objectives of high density and low defect levels.

Image and Text Guide

Figure 1. a Scanning electron microscope image of the alloy in the as‑fabricated condition. The weld pool is indicated by a dashed line. The heat‑affected zone and the weld‑pool boundary consist predominantly of fine equiaxed grains, whereas the interior of the weld pool is dominated by elongated columnar grains. b Columnar microstructure within the weld pool. c High‑magnification SEM energy‑dispersive spectroscopy (EDS) analysis of the equiaxed grain region reveals a relatively high density of Al3Zr precipitates, denoted by “Z.” d Inverse pole figure (IPF) map of the microstructure, with the weld pool outlined by a dashed line. The arrow in the lower‑right corner of the IPF legend indicates the build direction. The (100) pole figure shows that the grain orientations are random, with no distinct texture.

Figure 2. a Stress–strain curves for the as‑received, 8‑hour heat‑treated, and 48‑hour heat‑treated samples, adapted from reference 64; inset shows the strain‑hardening rate curve. b Visualization of the evolution of yield strength and ductility with varying heat‑treatment durations. c–e Fracture surfaces of the as‑received, 8‑hour, and 48‑hour heat‑treated samples; with increasing heat‑treatment time, both pit density and area fraction increase.

Figures 3a and 3b show the IPF and GROD maps, respectively, for the sample after 8 hours of deformation. In the IPF map, the arrows indicate the crystallographic orientation. Two grains with large local misorientations are highlighted. Figure 3c presents SEM images corresponding to the fields of view in the IPF map (a) and the GROD map (b). The regions rich in precipitates align with the fine-grained areas observed in the IPF map. In the GROD map, grains exhibiting significant local misorientations are enclosed by dashed boxes. Figures 3c‑1 and 3c‑2 depict the grains of interest—grain #1 and grain #2 SEM-EDS images. Both grains are surrounded by precipitate phases, where “N” denotes the Al3Ni precipitate and “T” denotes the ternary precipitate. Cavities were observed near both grains, resulting from strain incompatibility between the precipitates and the soft, ductile aluminum matrix.

Figures 4a, 4b, and 4c are scanning electron microscopy–energy-dispersive X-ray spectroscopy images that show the precipitates near pores in the samples at the as‑built condition, after 8 hours, and after 48 hours, respectively. The primary constituents are Al3Zr and Al3Ni, which jointly contribute to pore formation; the as‑built sample exhibits a higher fraction of Al3Zr, whereas the proportion of Al3Ni increases with prolonged exposure to elevated temperatures. Figure 4d presents a schematic illustration of the microstructural damage mechanisms in this material system under both the as‑built condition and high‑temperature conditions.

Figure 5. Correlation between the Pugh’s ratio and the normalized Pettifor’s Cauchy pressure for different binary Al precipitates. Al3Zr and Al3Ni are highlighted, and a hyperbolic function has been fitted to all data points. Both criteria indicate that Al3Zr is harder and more brittle than Al3Ni, and that both phases exhibit strain incompatibility with the Al matrix.

Figure 6. Contour plot of equilibrium phase fractions at 250°C. The red star indicates the composition of the reference alloy. As the Zr content decreases, the “golden ratio” line minimizes the Al3Zr phase while maximizing the L12 phase fraction. b Phase fractions obtained from Scheil simulations. Ni = 0.6 at.%; this suppresses the formation of Al3Ni while maximizing the ternary phase fraction.

Figure 7. The phase fractions of the baseline alloy and the design alloy were calculated using both the Scheil model and equilibrium simulations at 250°C.

Figure 8. Stress–strain curves for the baseline alloy and the designed high‑ductility alloy. Tensile tests on the high‑ductility alloy were repeated three times to ensure reproducibility of the results.

Figure 9. a Fracture surface of the designed alloy. b Pit size distribution for the reference alloy and the designed high‑ductility alloy. c Comparison of the ratio of pit areas and the average pit size between the reference alloy and the designed alloy. The larger and more densely distributed pits in the designed alloy indicate enhanced ductility.

Figure 10. Hardness evolution of the baseline alloy and the high‑ductility alloy during isothermal heat treatment at 400°C. The overall trends of the two curves are nearly parallel, indicating similar thermal responses. The newly designed alloy exhibits excellent thermal stability: after 48 hours, its hardness decreases by 15% compared with the as‑fabricated condition, whereas the baseline alloy shows a 11% reduction.

This study aims to develop aluminum alloys with both high strength and high ductility by employing rational microstructural design in conjunction with AMAZEMET’s high‑precision ultrasonic atomization technology, thereby meeting the demands of high‑temperature applications. Through simulations, experimental validation, and microstructural analysis, we leveraged AMAZEMET’s advanced atomization process to achieve precise control over the material’s microstructure, effectively enhancing its mechanical properties. Furthermore, by integrating state-of-the-art additive manufacturing techniques, we ensured the material’s practical manufacturability and superior performance in real‑world production. This research not only enriches the theoretical framework for designing high‑performance aluminum alloys but also provides a robust technical foundation and solid theoretical support for their broad application in aerospace, automotive, and other industries. Future work will focus on further improving the material’s thermal stability and fatigue resistance, accelerating the industrialization of high‑strength, high‑ductility aluminum alloys, and contributing to innovative advancements across relevant sectors.