Processing window for laser metal deposition of Al 7075 powder with minimized defects

Benoit, Michael J.; Sun, Shoujin; Brandt, Milan; Easton, Mark

doi:10.1016/j.jmapro.2021.02.031

Cited by 36 publications

(9 citation statements)

References 18 publications

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“…These images also evidence that clusters of TiC are still present after heat treatment, showing their good thermal stability. When compared to the microstructure reported in other works where multilayer samples of nonnanofunctionalized AA7075 were built using L-DED [18, 36,38], the eutectic features seen in Figure 3 are smaller and discontinuous, even though the energy input was similar in all cases. These results are consistent with earlier studies [13,14] that stated that the presence of TiC nanoparticles promotes the formation discontinuous eutectic features, which is beneficial in preventing crack formation.…”

Section: Resultsmentioning

confidence: 90%

Coaxial Wire Laser-based Additive Manufacturing of AA7075 with TiC Nanoparticles

Meneses,

Tuominen,

Ylä-Autio

et al. 2023

IOP Conf. Ser.: Mater. Sci. Eng.

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AA7075 is a heat treatable aluminium alloy widely used in aerospace and automotive applications due to its outstanding high strength-to-weight ratio. However, the implementation of this alloy in Additive Manufacturing (AM) processes has been limited due to its susceptibility to hot cracking. Moreover, selective evaporation of low boiling point elements Zn and Mg can cause gas porosity and diminish the mechanical properties of AM parts. Recent research revealed the effectiveness of nanoparticles additives to change the solidification behaviour of high-strength aluminium alloys and improve their weldability/printability. In this study, AA7075 enhanced with TiC nanoparticles was utilized as wire feedstock to create single and multi-layer samples with coaxial laser-directed energy deposition (L-DED). The response of the samples to precipitation hardening was studied, evaluating the microstructure and the microhardness before and after T6 heat treatment. Specimens were characterized using optical and electron microscopy and electron backscatter diffraction (EBSD). Crack-free and virtually porosity-free samples were fabricated, which exhibit a refined equiaxed grain structure with grain size <10μm. This confirms the ability of TiC nanoparticles to prevent columnar dendritic growth and promote heterogeneous nucleation. Microhardness values increased by 51 HV after T6 heat treatment and were uniform across the sample. Energy Dispersive Spectroscopy (EDS) analysis showed that there are evaporation losses of Zn and Mg. Considering the boiling temperatures of these elements, it is inferred that the molten pool reaches temperatures above 1090°C, and the partially melted zone temperature is between 907°C and 1090°C.

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Section: Resultsmentioning

confidence: 90%

Coaxial Wire Laser-based Additive Manufacturing of AA7075 with TiC Nanoparticles

Meneses,

Tuominen,

Ylä-Autio

et al. 2023

IOP Conf. Ser.: Mater. Sci. Eng.

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“…Metal vapor expulsion can result in the loss of elements through combustion [32], and the small particle smoke generated by the condensation of metal vapor can hinder the propagation of laser radiation. This reduction in laser energy input can result in unstable melting and an increased incidence of defects such as pores and incomplete fusion [19,20]. Moreover, alloys containing volatile elements, such as Zn, Mg, and Al [32][33][34][35][36] may experience changes in composition compared to the initial powder material due to elevated evaporation losses, leading to a significant deviation in final performance compared to expectations.…”

Section: Mainstream Metal Am Methods and Corresponding Inherent Defectsmentioning

confidence: 99%

Performance-control-orientated hybrid metal additive manufacturing technologies: state of the art, challenges, and future trends

Lv,

Liang,

et al. 2024

Int. J. Extrem. Manuf.

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Metal additive manufacturing (AM) technologies have made significant progress in the basic theoretical field since their invention in the 1970s. However, performance instability during continuous processing, such as thermal history, residual stress accumulation, and columnar grain epitaxial growth, consistently hinders their broad application in standardized industrial production. To overcome these challenges, performance-control-oriented hybrid AM (HAM) technologies have been introduced. These technologies, by leveraging external auxiliary processes, aim to regulate microstructural evolution and mechanical properties during metal AM. In this context, HAM technologies for molten pool regulation and solidified material deformation are identified as energy field-assisted AM (EFed AM, e.g., ultrasonic, electromagnetic, heat, etc.) technologies and interlayer plastic deformation-assisted AM (IPDed AM, e.g., laser shock peening, rolling, ultrasonic peening, friction stir process, etc.) technologies, respectively. A detailed and systematic review of performance-control-oriented HAM technologies is then provided. This review covers the influence of external energy fields on the melting, flow, and solidification behavior of materials, and the regulatory effects of interlayer plastic deformation on grain refinement, nucleation, and recrystallization. Furthermore, the role of performance-control-oriented HAM technologies in managing residual stress conversion, metallurgical defect closure, mechanical property improvement, and anisotropy regulation is thoroughly reviewed and discussed. The review concludes with an analysis of future development trends in EFed AM and IPDed AM technologies.

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“…There are four kinds of cracking mechanisms in LDED Al alloys, i.e. solidification cracks, liquation cracks, second phase induced cracks, and segregation induced liquation [96,100,101].…”

Section: 32mentioning

confidence: 99%

“…First, excessive energy input may generate tensile stresses on the solidified regions due to diverse thermal shrinkage degrees of the solidified and unsolidified regions, leading to solidification cracks. Once the residual liquid that flows into the interdendritic region is insufficient to compensate for the shrinkage discrepancy and thermal strain, the voids between solidifying grains may develop into solidification cracks [100,102], as shown in figures 5(a)-(d), which are common defects in LDED high strength Al alloys.…”

Section: 32mentioning

confidence: 99%

Review on laser directed energy deposited aluminum alloys

Liu,

Chen,

Qiu

et al. 2024

Int. J. Extrem. Manuf.

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The lightweight aluminum (Al) alloys have been widely used in frontier fields like aerospace and automotive industries, which attracts great interest in additive manufacturing to process high-value Al parts. As a mainstream additive manufacturing technique, laser directed energy deposition (LDED) shows good scalability to meet requirements for large-format components manufacturing and repairing. However, LDED Al alloys are highly challenging due to the inherent poor printability (e.g., low laser absorption, high oxidation sensitivity and cracking tendency). To further promote the development of LDED high-performance Al alloys, this review gains a deep understanding of the challenges and strategies to improve printability in LDED Al alloys. The porosity, cracking, distortion, inclusions, elements evaporation and resultant inferior mechanical properties (than laser powder bed fusion) are the key challenges in LDED Al alloys. Processing parameter optimizations, in-situ alloy design, reinforcing particle addition and field assistance are the efficient approaches to improve the printability and performance of LDED Al alloys. The underlying correlations between processes, alloy innovation, characteristic microstructures, and achievable performances in LDED Al alloys are discussed. The benchmarking mechanical properties and primary strengthening mechanism of LDED Al alloys are summarized. This review aims to provide a critical and in-depth evaluation of current progress in LDED Al alloys. The future opportunities and perspectives in LDED high-performance Al alloys are also outlooked.

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Processing window for laser metal deposition of Al 7075 powder with minimized defects

Cited by 36 publications

References 18 publications

Coaxial Wire Laser-based Additive Manufacturing of AA7075 with TiC Nanoparticles

Coaxial Wire Laser-based Additive Manufacturing of AA7075 with TiC Nanoparticles

Performance-control-orientated hybrid metal additive manufacturing technologies: state of the art, challenges, and future trends

Review on laser directed energy deposited aluminum alloys

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