scholarly journals Fatigue Improvement of AlSi10Mg Fabricated by Laser-Based Powder Bed Fusion through Heat-Treatment.

2021 ◽  
Author(s):  
Felix Sajadi ◽  
Jan-Marc Tiemann ◽  
Nooshin Bandari ◽  
Ali Cheloee Darabi ◽  
Javad Mola ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Fatigue Behavior ◽  
Fatigue Properties ◽  
Powder Bed Fusion ◽  
Microstructural Characteristics ◽  
Powder Bed ◽  
Treated Condition ◽  
Heat Treated ◽  
Treatment Parameter ◽  
Heat Treated Condition

This study aims to identify an optimal heat-treatment parameter set for an additively manufactured AlSi10Mg alloy in terms of increasing the hardness and eliminating the anisotropic microstructural characteristics of the alloy in as-built condition. Furthermore, the influence of these optimized parameters on the fatigue properties of the alloy investigated. In this respect, microstructural characteristics of an AlSi10Mg alloy manufactured by Laser-Based Powder Bed Fusion in non-heat-treated and heat-treated conditions were investigated. Their static and dynamic mechanical properties were evaluated, and fatigue behavior was explained by a detailed examination of fracture surfaces. Much of the microstructure in the non-heat-treated condition was composed of columnar grains oriented parallel to the build direction. Further analysis revealed a high fraction of pro-eutectic α-Al. Through heat-treatment, the alloy was successfully brought to its peak-hardened condition, while eliminating the anisotropic microstructural features. Yield strength and ductility increased simultaneously after heat-treatment, which is due to the relief of residual stresses, preservation of refined grains, and introduction of precipitation strengthening. The fatigue strength, calculated at 10^7 cycles, improved as well after heat-treatment and finally detailed fractography reviled that a more ductile fracture mechanism has happened in the heat-treated condition compared to the non-heat-treated condition.

scholarly journals Fatigue Improvement of AlSi10Mg Fabricated by Laser-Based Powder Bed Fusion through Heat Treatment

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 683
Author(s):  
Felix Sajadi ◽  
Jan-Marc Tiemann ◽  
Nooshin Bandari ◽  
Ali Cheloee Darabi ◽  
Javad Mola ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Fatigue Behavior ◽  
Fatigue Properties ◽  
Powder Bed Fusion ◽  
Microstructural Characteristics ◽  
Powder Bed ◽  
Treated Condition ◽  
Heat Treated ◽  
Treatment Parameter ◽  
Heat Treated Condition

This study aimed to identify an optimal heat-treatment parameter set for an additively manufactured AlSi10Mg alloy in terms of increasing the hardness and eliminating the anisotropic microstructural characteristics of the alloy in as-built condition. Furthermore, the influence of these optimized parameters on the fatigue properties of the alloy was investigated. In this respect, microstructural characteristics of an AlSi10Mg alloy manufactured by laser-based powder bed fusion in non-heat-treated and heat-treated conditions were investigated. Their static and dynamic mechanical properties were evaluated, and fatigue behavior was explained by a detailed examination of fracture surfaces. The majority of the microstructure in the non-heat-treated condition was composed of columnar grains oriented parallel to the build direction. Further analysis revealed a high fraction of pro-eutectic α-Al. Through heat treatment, the alloy was successfully brought to its peak-hardened condition, while eliminating the anisotropic microstructural features. Yield strength and ductility increased simultaneously after heat treatment, which is due to the relief of residual stresses, preservation of refined grains, and introduction of precipitation strengthening. The fatigue strength, calculated at 107 cycles, improved as well after heat treatment, and finally, detailed fractography revealed that a more ductile fracture mechanism occurred in the heat-treated condition compared to the non-heat-treated condition.

Study of Fatigue Properties of AISI4130 Steel Joined by Upset Welding in Heat Treated Condition

2012 ◽  
Vol 567 ◽  
pp. 54-57
Author(s):  
H. Mollazadeh ◽  
R. Nouruzi
Keyword(s):  
Fracture Surface ◽  
Weld Interface ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Final Fracture ◽  
Treated Condition ◽  
Heat Treated ◽  
Proeutectoid Ferrite ◽  
Heat Treated Condition ◽  
Interface Study

Resistance upset welding (UW) is a widely used for joining metals parts. In this research, the fatigue properties of AISI4130 steel joined by upset welding in annealed and quenched-tempered heat treated condition are investigated. Microstructure of weld and base metals was studied using optical microscopy. Tensile, impact and fatigue tests were performed and the final fracture surface was studied by scanning electron microscopy (SEM). The fatigue resistance is better for tempered martensite base metal than for the ferrite-pearlite and upset welded specimens. Results shows during the welding, proeutectoid ferrite phase forms at the interface which reduce the fatigue strength of welded specimens. Fractography of fatigue and tension welded samples indicated that in all samples fracture occurred in the middle of weld interface. Study of fracture surface of fatigue samples shows that the final fracture mode for welded samples is cleavage.

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

Materials ◽  
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.

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

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1290 ◽  
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.

Tensile and Fatigue Properties of Ti-6Al-4V Alloy Fabricated by Laser Powder-Bed Fusion Process

2020 ◽  
Author(s):  
M. Shafiqur Rahman ◽  
Uttam K. Chakravarty
Keyword(s):  
Fatigue Life ◽  
Fatigue Limit ◽  
Fatigue Behavior ◽  
Functional Materials ◽  
Fatigue Properties ◽  
Small Scale ◽  
Powder Bed Fusion ◽  
Cycle Fatigue ◽  
Laser Powder Bed Fusion ◽  
Powder Bed

Abstract The tensile and fatigue properties of laser-powder-bed-fusion (L-PBF) processed Ti-6Al-4V specimens are investigated at different loading conditions. Two types of as-built and post-machined L-PBF processed dogbone specimens are considered for the study, one is an ASTME8M round specimen and the other one is a customized small-scale flat structure. The tensile and fatigue behavior of the specimens are investigated numerically using the finite element (FE) method. The FE modeling considers both low cycle fatigue (LCF) and high cycle fatigue (HCF) test conditions by applying cyclic loads in fully-reversed and stress ratio R = 0.1 conditions. The FE results for the von Mises stress, strain, total deformation, fatigue life, factor of safety, and fatigue limit of the Ti-6Al-4V specimens are obtained at room temperature (295 K). Results obtained from the model show that the fatigue life decreases as the load increases. It is also found that fatigue life does not vary with the change of the test frequency under a specific fatigue load. The comparison of mechanical properties of the L-PBF processed specimens with conventionally manufactured Ti-6Al-4V parts is also shown to understand the differences in the tensile and fatigue behavior. The validation of the FE model is performed by comparing the numerical results for the yield stress and fatigue limit with the experimental results found from the literature. The overall study contains a detailed analysis of the tensile and fatigue behavior of additively manufactured Ti-6Al-4V parts and provides a guide to investigating the similar properties for other functional materials used in the L-PBF process.

Properties of Electroslag Steel 5ХНМ (5HNM) and 34 ХН1М (34HN1M) Melted with "Solid" Start Using Exothermic Fluxes

2016 ◽  
Vol 15 ◽  
pp. 25-34
Author(s):  
Anatoliy F. Vlasov ◽  
Natalja A. Makarenko ◽  
Anna M. Kushchiy ◽  
Dmitry A. Volkov ◽  
Denys M. Holub
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Molten Metal ◽  
Aluminum Powder ◽  
Conductive Layer ◽  
Electrically Conductive ◽  
Exothermic Reactions ◽  
Treated Condition ◽  
Heat Treated ◽  
Heat Treated Condition

The slag bath accelerated formation technological processes in the "solid" start of mono-and bifilar process schemes are worked out. The melted electroslag steel 5ХНМ (5HNM) and 34ХН1М (34HN1M) properties satisfy to the requirements that apply to the open wrought metal smelting mechanical properties. It is found that an effective way to enhance productivity is the electroslag processes exothermic flux (slag, ferroalloys, and aluminum powder in amounts sufficient to exothermic reactions) use. It is experimentally proved that an electrically conductive layer exothermic flux presence allows electroslag process, both in mono and bifilar schemes in "solid" start. The 34ХН1М (34HN1M) steel in non-heat treated condition tend to hairline cracks formation. The heat treatment provides the required mechanical properties and the hairline cracks absence in electroslag molten metal.

scholarly journals Mechanical and Tribological Behaviour of Artificially Aged (T6) Al-Zn-Mg-Cu Alloy

2020 ◽  
Vol 9 (3) ◽  
pp. 1988-1993
Keyword(s):  
Heat Treatment ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Aging Temperature ◽  
Cast Alloy ◽  
Intermetallic Phases ◽  
Mechanical And Tribological Properties ◽  
Treated Condition ◽  
Heat Treated ◽  
Heat Treated Condition

The present work deals with the effect of aging on the mechanical and tribological properties Al-Zn-Mg-Cu (AA7068) alloy. The mechanical properties such as tensile strength, compressive strength, hardness and sliding wear of the alloy in as cast and heat treated condition were examined in order to achieve the maximum properties. Microstructural examination of the alloy in as cast and heat treated condition was carried out to observe the effect of aging. SEM study was also done to observe the worn surfaces and the mechanism of material removal. It is observed that there is a substantial improvement in the mechanical and tribological properties of the alloy due to heat treatment as compared to the as cast alloy. The microstructural study of the cast alloy shows primary dendrites of aluminium and intermetallic phases around the inter-dendrites regions. Due to the heat treatment, the identity of the dendritic structure is lost, because of uniform distribution of precipitates, wherein intermetallic phases were seen dispersed within the grains and the grain boundaries. Results show that the tensile strength of the heat treated alloy at 210oC aging temperature has increased by 155% as compared to as cast alloy. The compressive strength and hardness of the alloy at 210oC aging temperature shows improvement of 41% and 54% respectively as compared to as cast alloy. Wear loss of the heat treated alloy at 210oC aging temperature has decreased at an applied load of 20, 40, 60 and 80 N in both 1.57m/s and 3.00m/s sliding speed.

scholarly journals Microstructure and Selective Corrosion of Alloy 625 Obtained by Means of Laser Powder Bed Fusion

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1742 ◽  
Author(s):  
Marina Cabrini ◽  
Sergio Lorenzi ◽  
Cristian Testa ◽  
Fabio Brevi ◽  
Sara Biamino ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Intergranular Corrosion ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Alloy 625 ◽  
Heat Treated ◽  
Selective Corrosion ◽  
Corrosion Susceptibility ◽  
Acid Test

The effect of microstructure on the susceptibility to selective corrosion of Alloy 625 produced by laser powder bed fusion (LPBF) process was investigated through intergranular corrosion tests according to ASTM G28 standard. The effect of heat treatment on selective corrosion susceptibility was also evaluated. The behavior was compared to commercial hot-worked, heat treated Grade 1 Alloy 625. The morphology of attack after boiling ferric sulfate-sulfuric acid test according to ASTM G28 standard is less penetrating for LPBF 625 alloy compared to hot-worked and heat-treated alloy both in as-built condition and after heat treatment. The different attack morphology can be ascribed to the oversaturation of the alloying elements in the nickel austenitic matrix obtained due to the very high cooling rate. On as-built specimens, a shallow selective attack of the border of the melt pools was observed, which disappeared after the heat treatment. The results confirmed similar intergranular corrosion susceptibility, but different corrosion morphologies were detected. The results are discussed in relation to the unique microstructures of LPBF manufactured alloys.

scholarly journals Computational analysis of the effects of geometric irregularities and post-processing steps on the mechanical behavior of additively manufactured 316L stainless steel stents

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0244463
Author(s):  
Lisa Wiesent ◽  
Ulrich Schultheiß ◽  
Philipp Lulla ◽  
Ulf Noster ◽  
Thomas Schratzenstaller ◽  
...  
Keyword(s):  
Stainless Steel ◽  
316L Stainless Steel ◽  
Mechanical Response ◽  
Lattice Structures ◽  
Powder Bed ◽  
Treated Condition ◽  
Expansion Behavior ◽  
Heat Treated ◽  
Heat Treated Condition ◽  
Radial Forces

Advances in additive manufacturing enable the production of tailored lattice structures and thus, in principle, coronary stents. This study investigates the effects of process-related irregularities, heat and surface treatment on the morphology, mechanical response, and expansion behavior of 316L stainless steel stents produced by laser powder bed fusion and provides a methodological approach for their numerical evaluation. A combined experimental and computational framework is used, based on both actual and computationally reconstructed laser powder bed fused stents. Process-related morphological deviations between the as-designed and actual laser powder bed fused stents were observed, resulting in a diameter increase by a factor of 2-2.6 for the stents without surface treatment and 1.3-2 for the electropolished stent compared to the as-designed stent. Thus, due to the increased geometrically induced stiffness, the laser powder bed fused stents in the as-built (7.11 ± 0.63 N) or the heat treated condition (5.87 ± 0.49 N) showed increased radial forces when compressed between two plates. After electropolishing, the heat treated stents exhibited radial forces (2.38 ± 0.23 N) comparable to conventional metallic stents. The laser powder bed fused stents were further affected by the size effect, resulting in a reduced yield strength by 41% in the as-built and by 59% in the heat treated condition compared to the bulk material obtained from tensile tests. The presented numerical approach was successful in predicting the macroscopic mechanical response of the stents under compression. During deformation, increased stiffness and local stress concentration were observed within the laser powder bed fused stents. Subsequent numerical expansion analysis of the derived stent models within a previously verified numerical model of stent expansion showed that electropolished and heat treated laser powder bed fused stents can exhibit comparable expansion behavior to conventional stents. The findings from this work motivate future experimental/numerical studies to quantify threshold values of critical geometric irregularities, which could be used to establish design guidelines for laser powder bed fused stents/lattice structures.

scholarly journals Unravelling the multi-scale structure–property relationship of laser powder bed fusion processed and heat-treated AlSi10Mg

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
P. Van Cauwenbergh ◽  
V. Samaee ◽  
L. Thijs ◽  
J. Nejezchlebová ◽  
P. Sedlák ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Grain Refinement ◽  
Rapid Solidification ◽  
Material Properties ◽  
Mechanical And Thermal Properties ◽  
Powder Bed Fusion ◽  
Structure Property ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Heat Treated

AbstractTailoring heat treatments for Laser Powder Bed Fusion (LPBF) processed materials is critical to ensure superior and repeatable material properties for high-end applications. This tailoring requires in-depth understanding of the LPBF-processed material. Therefore, the current study aims at unravelling the threefold interrelationship between the process (LPBF and heat treatment), the microstructure at different scales (macro-, meso-, micro-, and nano-scale), and the macroscopic material properties of AlSi10Mg. A similar solidification trajectory applies at different length scales when comparing the solidification of AlSi10Mg, ranging from mould-casting to rapid solidification (LPBF). The similarity in solidification trajectories triggers the reason why the Brody-Flemings cellular microsegregation solidification model could predict the cellular morphology of the LPBF as-printed microstructure. Where rapid solidification occurs at a much finer scale, the LPBF microstructure exhibits a significant grain refinement and a high degree of silicon (Si) supersaturation. This study has identified the grain refinement and Si supersaturation as critical assets of the as-printed microstructure, playing a vital role in achieving superior mechanical and thermal properties during heat treatment. Next, an electrical conductivity model could accurately predict the Si solute concentration in LPBF-processed and heat-treated AlSi10Mg and allows understanding the microstructural evolution during heat treatment. The LPBF-processed and heat-treated AlSi10Mg conditions (as-built (AB), direct-aged (DA), stress-relieved (SR), preheated (PH)) show an interesting range of superior mechanical properties (tensile strength: 300–450 MPa, elongation: 4–13%) compared to the mould-cast T6 reference condition.

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