Short Heat Treatments for the F357 Aluminum Alloy Processed by Laser Powder Bed Fusion

Abstract

Conventionally processed precipitation hardening aluminum alloys are generally treated with T6 heat treatments which are time-consuming and generally optimized for conventionally processed microstructures. Alternatively, parts produced by laser powder bed fusion (L-PBF) are characterized by unique microstructures made of very fine and metastable phases. These peculiar features require specifically optimized heat treatments. This work evaluates the effects of a short T6 heat treatment on L-PBF AlSi7Mg samples. The samples underwent a solution step of 15 min at 540 °C followed by water quenching and subsequently by an artificial aging at 170 °C for 2–8 h. The heat treated samples were characterized from a microstructural and mechanical point of view and compared with both as-built and direct aging (DA) treated samples. The results show that a 15 min solution treatment at 540 °C allows the dissolution of the very fine phases obtained during the L-PBF process; the subsequent heat treatment at 170 °C for 6 h makes it possible to obtain slightly lower tensile properties compared to those of the standard T6. With respect to the DA samples, higher elongation was achieved. These results show that this heat treatment can be of great benefit for the industry.

Aging Profiles of AlSi7Mg0.6 and AlSi10Mg0.3 Alloys Manufactured via Laser-Powder Bed Fusion: Direct Aging versus T6

“…Both microhardness values are recovered after AA HTs at 165 °C × 6 h reaching the peak-aging at 120 HV, and at 180 °C × 2 h with 118 HV of peak-aging. After the same SHT at 535 °C × 1 h, Casati et al [ 31 ] illustrated 78 HV increasing at 113 HV after an AA at 160 °C × 4 h. Higher HV values are discussed by Vanzetti et al [ 20 ], who studied an SHT at 540 °C × 15′ (102 ± 5 HV) followed by an AA at 170 °C × 6 h (132 ± 3 HV).…”

“…In relation to the contribution, its following mathematical model combines the volume fraction of the precipitates and their dimensions , as follows: where [-] is a material constant, [GPa] is the shear modulus of Al ( , [ 41 ]), is the Burger vector ( , [ 9 ]), and are the diameter and thickness of the precipitates, respectively. Equation (7) highlights an increase in material strengthening when the volume fraction increases, as is possible to detect in peak-aged samples [ 9 , 20 , 22 , 26 , 36 ]. The same results can be also obtained modifying the and values.…”

“…From a three-dimensional point of view, the eutectic particles formed a tubular structure arranged along with the build direction (i.e., parallel to the build platform) which confers UTS and YS higher than 360 MPa and 210 MPa, respectively, for the as-built AlSi10Mg0.3 alloy [ 9 ]. Comparable mechanical properties are shown by the as-built AlSi7Mg0.6 alloy [ 20 , 21 ]. As widely discussed in [ 9 , 22 ], the pre-heated (hot) build platform plays fundamental roles on both the precipitation phenomena and the residual stress amount and, consequently, on the obtained mechanical performance.…”

Effect of Short Heat Treatments on the Microstructural Evolution and Hardness of Thixoformed Graphene Reinforced Aluminium Composites

“…The several researchers have endeavoured to change the established T6 standard parameter to promote the dissolving process and facilitating the homogenisation of eutectic phases. Vanzetti et al (2021) applied a short solution treatment of 540 ℃ for 15 min, water quench and artificial ageing at 170 ℃ for 6 h on AlSi7Mg alloy. The eutectic Si network transformed to globularisation and the micrometric of Si particles distributed homogeneously in the 𝛼-Al phase.…”

Processability of A6061 Aluminum Alloy Using Laser Powder Bed Fusion by In Situ Synthesis of Grain Refiners

“…In fact, their printability is affected by several features such as high reflectivity, high thermal conductivity, and poor flowability of the powder [7]. Among traditional Al alloys, near-eutectic cast alloys such as AlSi10Mg [8][9][10][11][12][13], AlSi12 [14,15], and A357 [16][17][18] are the most studied and suitable for LPBF [2]. This is due to the high Si content, which improves both the processability and the printability of these alloys by enhancing the fluidity of the melted alloy, narrowing the solidification range [19], and increasing the fraction of absorbed energy [2].…”