Nanoparticles Enabled Mechanism for Hot Cracking Elimination in Aluminum Alloys

“…With respect to raw materials, additives such as Si can be included, that enhances the flowability and improves the backfilling of cracks during solidification [29,30]. 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].…”

Section: Introductionmentioning

confidence: 99%

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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“…7085 aluminum alloy is an ultra-high-strength heat-treatable reinforced aluminum alloy with a high-specific strength and specific stiffness, and an excellent processing performance. It has been widely used in aerospace, rail vehicles, and other fields [ 1 , 2 , 3 , 4 , 5 ]. In the casting process, the inclusions and gases in the melt have a great influence on the quality of the 7085 aluminum alloy ingot.…”

Section: Introductionmentioning

confidence: 99%

Ultrasonic Bending Vibration-Assisted Purification Experimental Study of 7085 Aluminum Alloy Melt

Chen

Liao

et al. 2022

Materials

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Aiming at the problem that melt inclusions in the casting process of 7085 aluminum alloy seriously affect the ingot quality, this study introduces ultrasonic bending vibration into the melt of the launder in the semi-continuous casting process of 7085 aluminum alloy and investigates the online purification effect of ultrasonic bending vibration on the melt of 7085 aluminum alloy through a metallographic analysis, SEM analysis, and EDS energy spectrum analysis. The results show that, under the action of the ultrasonic, the inclusions in the aluminum melt are transformed from a large number of elongated large inclusions with a size of more than 50 μm, and granular inclusions with a size of about 5–15 μm, into a small amount of smaller than 30 μm point-like small inclusions. In addition, the average area ratio of inclusions in the melted sample was reduced from 3.835 (±0.05)% to 0.458 (±0.05)%, and the residual refining agent in the aluminum melt was effectively removed. It was also found that under the action of ultrasonic bending vibration, the tiny inclusions in the melt aggregate with each other, and interact with the residual refining agent in the melt to further grow, and are attached to the inner surface of the ceramic cavity channel to be removed.

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Nanoparticles Enabled Mechanism for Hot Cracking Elimination in Aluminum Alloys

Cited by 73 publications

References 27 publications

Recent developments in the design, development, and analysis of the influence of external magnetic-field on gas-metal arc welding of non-ferrous alloys: review on optimization of arc-structure to enhance the morphology, and mechanical properties of welded joints for automotive applications

Recent developments in the design, development, and analysis of the influence of external magnetic-field on gas-metal arc welding of non-ferrous alloys: review on optimization of arc-structure to enhance the morphology, and mechanical properties of welded joints for automotive applications

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

Ultrasonic Bending Vibration-Assisted Purification Experimental Study of 7085 Aluminum Alloy Melt

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