Directed energy deposition of AA7075 - Effect of TiC nanoparticles on microstructure

Gonzalez, Lucia Cobian; Tuominen, Jari; Ahmed, Shahroz; Patnamsetty, Madan; Peura, Pasi

doi:10.1016/j.rinma.2022.100341

Cited by 5 publications

(9 citation statements)

References 32 publications

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“…DED processes are characterized by high thermal gradients along the building direction, which produces columnar grains [6,18,43]. The results in this case confirm the ability of TiC to promote nucleation and prevent the columnar structure as reported in literature [13,14,21,22,31]. The grain size in the as-built condition is 8-9μm, and after T6 it increased slightly to 9-10μm.…”

Section: Resultssupporting

confidence: 85%

“…Despite the loss of some Zn and Mg, composition values are still within the standard values for AA7075, and so is the hardness after heat treatment, which is indicated in literature to be around 160-175 HV for cast and wrought AA7075 after T6 [11,27]. Other studies have reported average values for L-DED processed AA7075 in T6 condition of 97 HV [27], 115 HV [21] and 145 HV [26]. These lower values were attributed to evaporation losses of Zn and Mg and to the presence of porosity.…”

Section: Resultsmentioning

confidence: 87%

“…First, liquid aluminium can quickly dissolve high amounts of hydrogen, and because the solubility rapidly decreases during solidification, most of this hydrogen precipitates as gas and generates pores [19,20]. Second, trapped gases generated for the evaporation of low-boiling-point elements zinc and magnesium (907°C and 1090°C, respectively) [21]. Furthermore, several studies have shown that Zn and Mg evaporation in 7xxx Al alloys also results in diminished hardness and tensile strength values in both as deposited and heat-treated states [18, [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

“…Second, trapped gases generated for the evaporation of low-boiling-point elements zinc and magnesium (907°C and 1090°C, respectively) [21]. Furthermore, several studies have shown that Zn and Mg evaporation in 7xxx Al alloys also results in diminished hardness and tensile strength values in both as deposited and heat-treated states [18, [21][22][23]. Moreover, contamination of the substrate or feedstock and shielding gas entrapment can also lead to gas porosity [18].…”

Section: Introductionmentioning

confidence: 99%

“…Likewise, studies have proved the efficiency of nanoparticles such as TiB2 and TiC to promote heterogenous nucleation and produce a refined equiaxed grain microstructure with better resistance to cracking as grains are more capable of rotating and deforming to accommodate the strains originated from solidification shrinkage [22,31,32]. This has enabled the building of crack-free samples of AA7075 using GTAW-based DED [12], powder-based L-DED [21] and PBF [30,33]. However, to the best of the authors' knowledge no reports exist that deal with coaxial wired L-DED of nanofunctionalized AA7075, which is a very promising processes because of the aforementioned advantages of wire-based methods over powder-based ones and considering that laser as energy source in DED processes offers the possibility to have shorter interaction times and higher cooling rates than arc-based methods, which controls micro-segregation and produces fine-grained microstructures [34,35].…”

Section: Introductionmentioning

confidence: 99%

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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: Resultssupporting

confidence: 85%

Section: Resultsmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

Meneses,

Tuominen,

Ylä-Autio

et al. 2023

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

View full text Add to dashboard Cite

show abstract

Microstructure and property enhancement of 7075 aluminium alloy via laser metal deposition augmented by in-situ ultrasonic vibration

Su,

Savinov,

Wang

et al. 2024

Virtual and Physical Prototyping

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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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Directed energy deposition of AA7075 - Effect of TiC nanoparticles on microstructure

Cited by 5 publications

References 32 publications

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

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

Microstructure and property enhancement of 7075 aluminium alloy via laser metal deposition augmented by in-situ ultrasonic vibration

Review on laser directed energy deposited aluminum alloys

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