Local laser hardening of heat treated medium manganese steel initially processed by laser powder bed fusion (LPBF)

Medium manganese steels can exhibit both high strength and ductility due to transformation-induced plasticity (TRIP), caused by metastable retained austenite, which in turn can be adjusted by intercritical annealing. This study addresses the laser additive processability and mechanical properties of the third-generation advanced high strength steels (AHSS) on the basis of medium manganese steel using Laser Powder Bed Fusion (LPBF). For the investigations, an alloy with a manganese concentration of 5 wt.% was gas atomized and processed by LPBF. Intercritical annealing was subsequently performed at different temperatures (630 and 770 °C) and three annealing times (3, 10 and 60 min) to adjust the stability of the retained austenite. Higher annealing temperatures lead to lower yield strength but an increase in tensile strength due to a stronger work-hardening. The maximum elongation at fracture was approximately in the middle of the examined temperature field. The microstructure and properties of the alloy were further investigated by scanning electron microscopy (SEM), hardness measurements, X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and element mapping.

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Effect of Build Orientation on the Microstructure, Mechanical and Corrosion Properties of a Biodegradable High Manganese Steel Processed by Laser Powder Bed Fusion

Metals ◽

10.3390/met11060944 ◽

2021 ◽

Vol 11 (6) ◽

pp. 944

Author(s):

Martin Otto ◽

Stefan Pilz ◽

Annett Gebert ◽

Uta Kühn ◽

Julia Hufenbach

Keyword(s):

Electron Backscatter Diffraction ◽

Longitudinal Axis ◽

Manganese Steel ◽

Compressive Yield Strength ◽

Powder Bed Fusion ◽

Compression Tests ◽

Laser Powder Bed Fusion ◽

Corrosion Properties ◽

Powder Bed ◽

Manufacturing Technologies

In the last decade, additive manufacturing technologies like laser powder bed fusion (LPBF) have emerged strongly. However, the process characteristics involving layer-wise build-up of the part and the occurring high, directional thermal gradient result in significant changes of the microstructure and the related properties compared to traditionally fabricated materials. This study presents the influence of the build direction (BD) on the microstructure and resulting properties of a novel austenitic Fe‑30Mn‑1C‑0.02S alloy processed via LPBF. The fabricated samples display a {011} texture in BD which was detected by electron backscatter diffraction. Furthermore, isolated binding defects could be observed between the layers. Quasi-static tensile and compression tests displayed that the yield, ultimate tensile as well as the compressive yield strength are significantly higher for samples which were built with their longitudinal axis perpendicular to BD compared to their parallel counterparts. This was predominantly ascribed to the less severe effects of the sharp-edged binding defects loaded perpendicular to BD. Additionally, a change of the Young’s modulus in dependence of BD could be demonstrated, which is explained by the respective texture. Potentiodynamic polarization tests conducted in a simulated body fluid revealed only slight differences of the corrosion properties in dependence of the build design.

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The role of texturing and microstructure evolution on the tensile behavior of heat-treated Inconel 625 produced via laser powder bed fusion

Materials Science and Engineering A ◽

10.1016/j.msea.2019.138500 ◽

2020 ◽

Vol 769 ◽

pp. 138500 ◽

Cited By ~ 16

Author(s):

Giulio Marchese ◽

Simone Parizia ◽

Masoud Rashidi ◽

Abdollah Saboori ◽

Diego Manfredi ◽

...

Keyword(s):

Microstructure Evolution ◽

Tensile Behavior ◽

Inconel 625 ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed ◽

Heat Treated

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

Materials ◽

10.3390/ma14206157 ◽

2021 ◽

Vol 14 (20) ◽

pp. 6157

Author(s):

Matteo Vanzetti ◽

Enrico Virgillito ◽

Alberta Aversa ◽

Diego Manfredi ◽

Federica Bondioli ◽

...

Keyword(s):

Heat Treatment ◽

Precipitation Hardening ◽

Solution Treatment ◽

Heat Treatments ◽

Point Of View ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed ◽

Heat Treated ◽

Direct Aging

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.

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Effect of Laser Shock Peening on Properties of Heat-Treated Ti–6Al–4V Manufactured by Laser Powder Bed Fusion

International Journal of Precision Engineering and Manufacturing-Green Technology ◽

10.1007/s40684-020-00234-2 ◽

2020 ◽

Cited By ~ 1

Author(s):

Inkyu Yeo ◽

Seongguk Bae ◽

Auezhan Amanov ◽

Sungho Jeong

Keyword(s):

Laser Shock Peening ◽

Powder Bed Fusion ◽

Laser Shock ◽

Laser Powder Bed Fusion ◽

Powder Bed ◽

Heat Treated ◽

Shock Peening

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Dynamic-loading behavior and anisotropic deformation of pre- and post-heat-treated IN718 fabricated by laser powder bed fusion

Additive Manufacturing ◽

10.1016/j.addma.2020.101083 ◽

2020 ◽

Vol 33 ◽

pp. 101083 ◽

Cited By ~ 1

Author(s):

Nadia Kouraytem ◽

Raphaël A. Chanut ◽

Dillon S. Watring ◽

Timmanee Loveless ◽

John Varga ◽

...

Keyword(s):

Dynamic Loading ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed ◽

Heat Treated ◽

Anisotropic Deformation

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Laser Powder Bed Fusion of Inconel 718: Residual Stress Analysis Before and After Heat Treatment

Metals ◽

10.3390/met9121290 ◽

2019 ◽

Vol 9 (12) ◽

pp. 1290 ◽

Cited By ~ 19

Author(s):

Rafael Barros ◽

Francisco J. G. Silva ◽

Ronny M. Gouveia ◽

Abdollah Saboori ◽

Giulio Marchese ◽

...

Keyword(s):

Heat Treatment ◽

Lateral Surface ◽

Extreme Temperature ◽

Hole Drilling ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed ◽

Tensile Stresses ◽

Compressive Stresses ◽

Heat Treated

Residual stresses (RS) of great magnitude are usually present in parts produced by Laser Powder Bed Fusion (PBF-LB), mainly owing to the extreme temperature gradients and high cooling rates involved in the process. Those “hidden” stresses can be detrimental to a part’s mechanical properties and fatigue life; therefore, it is crucial to know their magnitude and orientation. The hole-drilling strain-gage method was used to determine the RS magnitude and direction-depth profiles. Cuboid specimens in the as-built state, and after standard solution annealing and ageing heat treatment conditions, were prepared to study the RS evolution throughout the heat treatment stages. Measurements were performed on the top and lateral surfaces. In the as-built specimens, tensile stresses of ~400 MPa on the top and above 600 MPa on the lateral surface were obtained. On the lateral surface, RS anisotropy was noticed, with the horizontally aligned stresses being three times lower than the vertically aligned. RS decreased markedly after the first heat treatment. On heat-treated specimens, magnitude oscillations were observed. By microstructure analysis, the presence of carbides was verified, which is a probable root for the oscillations. Furthermore, compressive stresses immediate to the surface were obtained in heat-treated specimens, which is not in agreement with the typical characteristics of parts fabricated by PBF-LB, i.e., tensile stresses at the surface and compressive stresses in the part’s core.

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