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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
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
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 ...
Konferenzveröffentlichung
On the Challenges toward Realization of Functionally Graded Structures by Electron Beam Melting—Fe-Base Shape Memory Alloy and Stainless Steel
(ASTM International, 2020-09-22)
In the present study, an iron-manganese-aluminum-nickel (Fe-Mn-Al-Ni) shape memory alloy was processed on an austenitic steel (AISI 304) build platform by electron beam melting in order to study the feasibility of realizing functionally graded structures consisting of two different materials (i.e., a functional and a structural material). Compression specimens consisting of the processed shape memory alloy and the austenitic build platform in equal parts were investigated. The microstructure was analyzed in the ...
Aufsatz
Energy Resolved Residual Stress Analysis with Laboratory X-Ray Sources
(2017-04-17)
It is well known that existing residual stress fields play an important role for strength and lifetime of components. Consequently there is a great interest in the availability of fast, reliable and possibly nondestructive methods for their determination. In this context, X-ray diffraction methods play an important role in technical practice as well as in scientific research. They are based on the determination of lattice strains from which residual stresses are determined applying Hooke's law with appropriate elastic ...
Aufsatz
Pathways toward the Use of Non-Destructive Micromagnetic Analysis for Porosity Assessment and Process Parameter Optimization in Additive Manufacturing of 42CrMo4 (AISI 4140)
(2024-02-20)
Laser-based powder bed fusion of metals (PBF-LB/M) is a widely applied additive manufacturing technique. Thus, PBF-LB/M represents a potential candidate for the processing of quenched and tempered (Q&T) steels such as 42CrMo4 (AISI 4140), as these steels are often considered as the material of choice for complex components, e.g., in the toolmaking industry. However, due to the presence of process-induced defects, achieving a high quality of the resulting parts remains challenging in PBF-LB/M. Therefore, an extensive ...
Aufsatz
Bend Straightening of a Carbonitrided Gear Shaft – Consequences on Residual Stresses and Retained Austenite near the Surface
(2017-06-20)
Carbonitriding of shafts in drive technology is strongly connected with distortion. Bend straightening is an important process step in order to eliminate distortion without removing the hardened surface layer. As shown in several investigations, even for simple part geometries, bending induced stresses and plastic deformations have a strong impact not only on the residual stress state but also on the microstructure after straightening. As gear shafts become increasingly filigree and complex in their geometry, the ...
Aufsatz
On the low-cycle fatigue behavior of thermo-mechanically processed high-strength aluminum alloys
(2021)
In the present work low-cycle fatigue experiments were carried out on thermo-mechanically processed AA6082 and AA7075 sheets to evaluate mechanical properties under cyclic loading. Different cooling rates imposed by use of tempered forming tools after solutionizing and subsequent aging treatment led to the formation of precipitates with differing sizes and morphologies. Specimens thermo-mechanically processed in tools with temperatures of 24 °C and 200 °C showed superior mechanical properties under both monotonic and ...