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Investigation of processing windows in additive manufacturing of AlSi10Mg for faster production utilizing data-driven modeling
(2022-04-29)
To reduce production time and decrease production cost, the increase of layer thickness is an adequate option in powder bed fusion. In order to determine the relationships between process parameters in laser powder bed fusion (PBF-LB/M) and final porosity in AlSi10Mg, samples were processed following a space-filling experimental design in the present study. A total of 144 samples were fabricated considering layer thicknesses of 30 µm, 45 µm, 60 µm, and 90 µm. Afterwards, porosity was assessed using image analysis and ...
Aufsatz
Influence of Surface Mechanical Attrition Treatment (SMAT) on Microstructure, Tensile and Low-Cycle Fatigue Behavior of Additively Manufactured Stainless Steel 316L
(2023-08-29)
Direct Energy Deposition (DED), as one common type of additive manufacturing, is capable of fabricating metallic components close to net-shape with complex geometry. Surface mechanical attrition treatment (SMAT) is an advanced surface treatment technology which is able to yield a nanostructured surface layer characterized by compressive residual stresses and work hardening, thereby improving the fatigue performances of metallic specimens. In the present study, stainless steel 316L specimens were fabricated by DED and ...
Aufsatz
On the influence of ϰ-carbides on the low-cycle fatigue behavior of high-Mn light-weight steels
(2021)
High-manganese light-weight steels offer a great potential for structural purposes in the mobility sector due to their reduced density combined with outstanding mechanical properties. As many of the envisaged applications of these materials will suffer from cyclic loading during their service life, the fundamentals of their fatigue behavior must be studied extensively. In the present work, the low-cycle fatigue (LCF) properties of an austenitic Fe-29.8Mn-7.65Al-1.11C light-weight steel were investigated. Two ...
Aufsatz
On the structural integrity of Fe-36Ni Invar alloy processed by selective laser melting
(2020)
Specimens made from pre-alloyed Invar (Fe-36Ni) powder were fabricated by selective laser melting and stress-relief heat treated afterwards. A relative density of the fabricated parts of 99.6 % was determined by computed tomography. The microstructure and mechanical behavior under monotonic and particularly cyclic loading at ambient temperature were investigated. Results reveal a bimodal microstructure containing columnar and equiaxed grains with an average grain size of 75 μm and pronounced texture 〈001〉 || BD. The ...
Aufsatz
Cyclic degradation of Co49Ni21Ga30 high-temperature shape memory alloy - On the roles of dislocation activity and chemical order
(2015)
Conventional shape memory alloys (SMAs), such as binary Ni-Ti, are typically limited to service temperatures below 100 °C. Recent studies on Co-Ni-Ga high temperature (HT) SMAs revealed the potential that these alloys can be used up to temperatures of about 400 °C. Analysis of the cyclic functional properties showed that degradation in these alloys is mainly triggered by intensive dislocation motion. However, data on the cyclic stress-strain response and the mechanisms leading to functional degradation of Co-Ni-Ga ...
Aufsatz
On the Effect of Quenching on Postweld Heat Treatment of Friction-Stir-Welded Aluminum 7075 Alloy
(2019)
This work focuses on the effect of postweld heat treatment (PWHT) on the mechanical properties and microstructural evolution of aluminum 7075 alloy processed via friction stir welding (FSW). FSW is known to be capable of grain refinement in the nugget zone (NZ). Two different quench media (water and air) were employed for PWHT. Regardless of the quench media, the PWHT led to the occurrence of grain growth in the NZ of the FSWed aluminum 7075 alloy. Abnormal grain growth occurred in the water quenched specimen. It is ...
Aufsatz
On the Friction Stir Processing of Additive-Manufactured 316L Stainless Steel
(2022)
The novel combination of friction stir processing (FSP) and additive manufacturing (AM) is studied herein. Laser-based powder bed fusion of metals (PBF-LB/M) is used to establish 316 L stainless steel with a bimodal microstructure. Upon FSP, the as-built bimodal microstructure with an average grain size of 179 μm is transformed into the unimodal microstructure containing ultrafine grains with an average grain size of 1.2 μm. Results obtained by mechanical testing reveal that after FSP; the hardness, the yield point, ...
Aufsatz
Cyclic Deformation Response of Ultra-fine Grained Titanium at Elevated Temperatures
(2019)
This study focuses on the high-temperature cyclic deformation response (CDR) of ultra-fine grained (UFG) titanium of commercial purity (grade 4) processed via equal channel angular extrusion as a severe plastic deformation method. Low-cycle fatigue experiments were conducted at elevated temperatures up to 600 °C and at strain amplitudes ranging from 0.2% to 0.6%. Besides temperature and strain amplitude, the influence of two processing routes (8BC and 8E) on the fatigue characteristics of UFG Ti was examined. It is ...
Aufsatz
Effect of grain size on the very high cycle fatigue behavior and notch sensitivity of titanium
(2019)
The very high-cycle fatigue performances of coarse-grained and ultrafine-grained titanium samples with different geometries at ambient temperature and various stress amplitudes were investigated. Severe plastic deformation improves monotonic strength of titanium at the cost of a loss in ductility. Ultrafine-grained titanium demonstrates a superior fatigue performance compared to that of coarse-grained counterparts in the high-cycle fatigue regime, however, suffers notch sensitivity. Furthermore, in the very high-cycle ...
Aufsatz
Oxide Modified Iron in Electron Beam Powder Bed Fusion - From Processability to Corrosion Properties
(2022-03-07)
Additive manufacturing (AM) processes are not solely used where maximum design freedom meets low lot sizes. Direct microstructure design and topology optimization can be realized concomitantly during processing by adjusting the geometry, the material composition, and the solidification behavior of the material considered. However, when complex specific requirements have to be met, a targeted part design is highly challenging. In the field of biodegradable implant surgery, a cytocompatible material of an application-adapted ...