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Aufsatz
Relaxation properties of polyoxymethylene and ethylene–octene copolymer blend in solid and melt states
(2012-08-30)
Rheological properties of polyoxymethylene (POM) and ethylene–octene copolymer (EOC) in solid and melt states were investigated. Blends were prepared with a twin screw extruder at broad component wt-to-wt ratios (10, 30, 50, 70, 90 wt% of EOC). The morphology as well as calorimetric, rheological, and elastic properties of the blends were studied. The investigation showed that POM/EOC blends were heterogeneous in nature and had a broad phase transition region between 30 and 70 wt% of POM. Because during processing ...
Aufsatz
Martensite aging in ⟨001⟩ oriented Co₄₉ Ni₂₁ Ga₃₀ single crystals in tension
(2018-03-22)
Co–Ni–Ga high-temperature shape memory alloys (HT-SMAs) are well-known candidate materials for damping applications at elevated temperatures. Recent studies showed that upon heat treatment in stress-induced martensite under compressive loads transformation temperatures can be increased significantly, qualifying Co–Ni–Ga for HT-actuation. The increase in transformation temperatures is related to a change in chemical order recently validated via neutron diffraction experiments. Since SMAs show distinct tension–compression ...
Aufsatz
Electron beam welding of Fe–Mn–Al–Ni shape memory alloy: Microstructure evolution and shape memory response
(2017-07-03)
The present study reports on the impact of abnormal grain growth (AGG) on the microstructural evolution following electron beam (EB) welding of Fe–Mn–Al–Ni shape memory alloy (SMA). Polycrystalline sheet-like material was EB-welded and a cyclic heat treatment, studied in previous work, was conducted for inducing AGG and a bamboo-like microstructure, respectively. Optical and electron microscopy were carried out to characterize the prevailing microstructure upon cyclic heat treatment. For characterization of the ...
Aufsatz
Processing effects on tensile superelastic behaviour of Fe43.5Mn34Al15 ± XNi7.5∓X shape memory alloys
(2019)
Fe₄₃.₅Mn₃₄Al₁₅Ni₇.₅ was introduced in the current decade as a new superelastic alloy with great applicative potential due to: (i) superelastic behaviour over a thermal range of 200°C and (ii) recoverable strains up to 9.7 %. One of the key factors in enhancing the superelastic response of several shape memory alloys (SMAs) is the formation of an oligocrystalline structure, i.e. without triple junctions between grains, which is the result of an abnormal grain growth (AGG) process that can be induced by cyclic heat ...
Aufsatz
Design of novel materials for additive manufacturing - Isotropic microstructure and high defect tolerance
(2018-01-22)
Electron Beam Melting (EBM) is a powder-bed additive manufacturing technology enabling the production of complex metallic parts with generally good mechanical properties. However, the performance of powder-bed based additively manufactured materials is governed by multiple factors that are difficult to control. Alloys that solidify in cubic crystal structures are usually affected by strong anisotropy due to the formation of columnar grains of preferred orientation. Moreover, processing induced defects and porosity ...
Aufsatz
Shape memory effect and superelasticity in high-strength FeNiCoAlTi single crystals hardened by nanoparticles
(2019-11-19)
For [001]-oriented single crystals of Fe-28Ni-17Co-11.5Al-2.5Ti (at %) alloy in tension, it was shown that particles of the γ’-phase with a size of 4–6 nm lead to the appearance of superelasticity, with a strain of εSE=4.5% and a shape memory effect of εSME=5.9%. Increasing the particle size to 10–12 nm reduces εSE to 3.6% and εSME to 3.5%. The paper discusses the causes of the influence of particle size on the reversible strain.
Buch
Thermo-mechanische Gradierung eigenverstärkter Polypropylen-Composite
(kassel university press, 2015)
Eigenverstärkte Polypropylen-Composite weisen ein enormes Leichtbaupotential und überdurchschnittliche mechanische Grundeigenschaften auf. Das Eigenschaftsspektrum lässt sich auf die makromolekulare Orientierung oder sog. Eigenverstärkung der eingesetzten textilen Faser- und Bändchenhalbzeuge zurückführen, welche die Ausgangsbasis der Schichtverbunde bilden. Über eine gezielte Prozessführung kann die Eigenverstärkung bis ins heißkompaktierte Bauteil hinein kontrolliert und erhalten werden, wobei sich das Eigenschaftsspektrum ...
Buch
Rotatives Vibrationsschweißen
(kassel university press, 2017)
Schweißversuche mit den von dem Schweißmaschinenhersteller Fischer Kunststoff-Schweißtechnik GmbH entwickelten Prototypenmaschinen für das neuartige Rotative Vibrationsschweißen zeigen eine vergleichbare erforderliche Prozessführung und die bereits bekannten Ausprägungen der vier Schweißprozessphasen anderer Vibrationsschweißverfahren. Unter Verwendung unterschiedlicher Werkstoffe und Probekörpergeometrien zeigt sich, dass sich die Fügenahteigenschaften von mit dem Rotativen Vibrationsschweißverfahren gefügten ...
Aufsatz
Promoting abnormal grain growth in Fe-based shape memory alloys through compositional adjustments
(2019-05-28)
Iron-based shape memory alloys are promising candidates for large-scale structural applications due to their cost efficiency and the possibility of using conventional processing routes from the steel industry. However, recently developed alloy systems like Fe–Mn–Al–Ni suffer from low recoverability if the grains do not completely cover the sample cross-section. To overcome this issue, here we show that small amounts of titanium added to Fe–Mn–Al–Ni significantly enhance abnormal grain growth due to a considerable ...