Effect of heat treatments on pore morphology and microstructure of laser additive manufactured parts

Zhang, Bin; Meng, W. J.; Shao, Shuai; Phan, Nam; Shamsaei, Nima

doi:10.1002/mdp2.29

Cited by 15 publications

(7 citation statements)

References 29 publications

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“…The red profile (T6 heat treatment) has lower relative frequencies for small pores (<10 lm) than the black one (as-built) and higher relative frequencies for pores with an equivalent diameter >10 lm. The density variation after the T6 heat treatment can caused by the previously discussed phenomena ( Refs 39,40,42). In addition, this variation can also occur due to the microstructural variation taking place during the SHT (Fig.…”

Section: Microstructure and Porosities Before And After Heat Treatmentsmentioning

confidence: 86%

Defect-Correlated Vickers Microhardness of Al-Si-Mg Alloy Manufactured by Laser Powder Bed Fusion with Post-process Heat Treatments

Cerri

Ghio

Bolelli

2022

J. of Materi Eng and Perform

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Laser powder bed fusion is an additive manufacturing process characterized by different advantages like the manufacture of samples with complex geometry without the use of tools and/or molds. Generally, the manufactured samples are characterized by high tensile strengths which, however, can be affected by the presence of defects due to the unoptimized process parameters. In a large applications field, a low density of the as-built AlSi10Mg samples is a very important parameter to considered, e.g., due to both the loss of the tensile strengths correlated with a premature failure of the samples and the increase in time and costs associated with the manufacturing process. In addition, different post-process heat treatments can increase these effects leading to an ineffective manufacturing process. In this scenario, the present work shows the analysis of spherical and lack-of-fusion pores induced by the laser powder bed fusion process on the AlSi10Mg samples and their variations after different heat treatments (direct aging and T6). At the same time, the influence of pores on the Vickers microhardness and the tensile properties has been studied in the same AlSi10Mg samples (bars and billets) that were printed with single- and double-laser machine setup. Different process parameters were also analyzed and compared. The study was supported by the microstructural and pore analysis performed by optical microscopy along the XZ plane (build direction) and the XY plane. Finally, the greatest effects of pores were observed on the Vickers microhardness values; in fact, two different relationships between microhardness and density variation are discussed. The T6 heat treatment leads to a rounding of the pores already formed in the as-built samples and to a formation of new small pores. Graphical Abstract

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Section: Microstructure and Porosities Before And After Heat Treatmentsmentioning

confidence: 86%

Defect-Correlated Vickers Microhardness of Al-Si-Mg Alloy Manufactured by Laser Powder Bed Fusion with Post-process Heat Treatments

Cerri

Ghio

Bolelli

2022

J. of Materi Eng and Perform

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“…Other authors have shown that with the increase of SHT temperature the gas pressure increases and, if the temperature is able to reduce the yield strength of the material around the pore, it can deform it [9,25]. It is certainly possible to say that the pores may spheroidize to minimize the free surface energy as expressed by the Young-Laplace equation [22]. On the other hand, some other authors do not highlight the variation in density after the T6 HT [60,61].…”

Section: Mechanical Propertiesmentioning

confidence: 98%

“…Moreover, the full-cellular structure of the Si eutectic network in the α-Al matrix that is formed, in addition to the Orowan looping behaviour, make the mechanical properties of the AlSi10Mg SLMed higher than the same casting alloy. As matter of fact, the SLMed samples show YS between 250 and 300 MPa, UTS ≤ 400 MPa and strain at failure ≤7% rather than YS between 90 and 110 MPa and UTS between 190 and 210 MPa of casting alloy [4,8,[19][20][21][22][23][24][25]. Additionally, the use of a preheated build platform usually in the range between 150 and 200 • C can increase the mechanical properties of as-built samples due to the aging phenomena [26].…”

Section: Introductionmentioning

confidence: 99%

Work Hardening of Heat-Treated AlSi10Mg Alloy Manufactured by Selective Laser Melting: Effects of Layer Thickness and Hatch Spacing

Ghio

Cerri

2021

Materials

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The present study analyzed the microstructure and the mechanical properties of AlSi10Mg SLMed bars (10 × 10 × 300 mm) and billets (10 × 100 × 300 mm) before and after the direct aging at 200 °C for 4 h and the T6 heat treatment. The discussed results are compared to those obtained by the AlSi10Mg samples manufactured with the same geometry but using different process parameters (layer thickness higher than 40 μm and a hatch spacing lower than 100 μm) and also through the Quality Index (QI). These work conditions allow the obtaining of a microstructural variation and different tensile properties in as-built top samples. In both batches, the cycle time was 45 h and together with the preheated build platform at 150 °C, induced an increase of UTS (Ultimate Tensile Strength) and yield strength on the bottom rather than the top samples due to the aging phenomena. Upon completion of the direct aging heat treatment, the effects induced by the platform were cancelled, keeping a full cellular microstructure that characterized the as-built SLMed (Selective Laser Melted) samples. Moreover, the Considère criterion and the work hardening analysis showed that the failure occurs after the necking formation in some of the T6 heat-treated samples. In this last case, the Si eutectic network globularized into Si particles, causing a decrease of UTS (from around 400 MPa to 290 MPa) in favour of an increase of ductility up to 15% and reaching a QI in the range 400 ÷ 450 MPa. These values place these samples between the high-quality aluminium cast alloy and T6 heat-treated ones.

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“…This is definitely seen to be beneficial and the accepted practice for cast and wrought alloys. However, for materials processed using AM, the benefits tend to be less definitive and have in certain cases been found to have a somewhat limited effect [126][127][128][129][130][131][132][133][134][135][136][137][138].…”

Section: Hot Isostatic Pressing and Heat Treatmentmentioning

confidence: 99%

Challenges in Qualifying Additive Manufacturing for Turbine Components: A Review

Srinivasan

2021

Trans Indian Inst Met

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Gas turbine engine advancements have been enabled by innovation in materials and manufacturing technologies. The evolution of additive manufacturing (AM) has changed the face of direct digital technologies for the rapid production of models, prototypes, and functional parts including repair and maintenance for turbine engines. Metal 3D printing is poised to be an enabler for the next industrial revolution in enabling advancements in turbine engine performance. While there has been tremendous efforts on research and development in utilizing this versatile technology, the number of qualified metallic parts that are running in the engine has not been commensurate with the applied research and development efforts and the benefits that the AM technology offers. This review addresses some of the key technical issues that are currently limiting the prolific usage of AM as a successful vehicle for accelerated progress in gas turbine engines.

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Effect of heat treatments on pore morphology and microstructure of laser additive manufactured parts

Cited by 15 publications

References 29 publications

Defect-Correlated Vickers Microhardness of Al-Si-Mg Alloy Manufactured by Laser Powder Bed Fusion with Post-process Heat Treatments

Defect-Correlated Vickers Microhardness of Al-Si-Mg Alloy Manufactured by Laser Powder Bed Fusion with Post-process Heat Treatments

Work Hardening of Heat-Treated AlSi10Mg Alloy Manufactured by Selective Laser Melting: Effects of Layer Thickness and Hatch Spacing

Challenges in Qualifying Additive Manufacturing for Turbine Components: A Review

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