Microstructural Investigations of Novel High Temperature Alloys Based on NiAl-(Cr,Mo)

Apart from the reported transition from the fibrous morphology in NiAl-34Cr to lamellae by adding 0.6 at.% Mo, further morphology transformations along the eutectic trough in the NiAl-(Cr,Mo) alloys were observed. Compositions with at least 10.3 at.% Cr have lamellar morphology while the first tendency to fiber formation was found at 9.6 at.% Cr. There is a compositional range, where both lamellae and fibers are present in the microstructure and a further decrease in Cr to 1.8at.% Cr results in fully fibrous morphology. Alongside these morphology changes of the (Cr,Mo)$_{ss}$ reinforcing phase, its volume fraction was found to be from 41 to 11 vol.% confirming the trend predicted by the CALPHAD approach. For mixed morphologies in-situ X-ray diffraction experiments performed between room and liquidus temperature accompanied by EDX measurements reveal the formation of a gradient in composition for the solid solution. A new Mo-rich NiAl-9.6Cr-10.3Mo alloy clearly shows this effect in the as-cast state. Moreover, crystallographic orientation examination yields two different types of colonies in this composition. In the first colony type, the orientation relationship between NiAl matrix and (Cr,Mo)$_{ss}$ reinforcing phase was (100)$_{NiAl||}$ (100) $_{Cr,Mo}$ and ⟨100⟩ $_{NiAl||}$ ⟨100⟩ $_{Cr,Mo}$. An orientation relationship described by a rotation of almost 60° about ⟨111⟩ was found in the second colony type. In both cases, no distinct crystallographic plane as phase boundary was observe

A zone melting device for the in situ observation of directional solidification using high-energy synchrotron x rays editors-pick

Directional solidification (DS) is an established manufacturing process to produce high-performance components from metallic materials with optimized properties. Materials for demanding high-temperature applications, for instance in the energy generation and aircraft engine technology, can only be successfully produced using methods such as directional solidification. It has been applied on an industrial scale for a considerable amount of time, but advancing this method beyond the current applications is still challenging and almost exclusively limited to post-process characterization of the developed microstructures. For a knowledge-based advancement and a contribution to material innovation, in situ studies of the DS process are crucial using realistic sample sizes to ensure scalability of the results to industrial sizes. Therefore, a specially designed Flexible Directional Solidification (FlexiDS) device was developed for use at the P07 High Energy Materials Science beamline at PETRA III (Deutsches Elektronen–Synchrotron, Hamburg, Germany). In general, the process conditions of the crucible-free, inductively heated FlexiDS device can be varied from 6 mm/h to 12 000 mm/h (vertical withdrawal rate) and from 0 rpm to 35 rpm (axial sample rotation). Moreover, different atmospheres such as Ar, N2, and vacuum can be used during operation. The device is designed for maximum operation temperatures of 2200 °C. This unique device allows in situ examination of the directional solidification process and subsequent solid-state reactions by x-ray diffraction in the transmission mode. Within this project, different structural intermetallic alloys with liquidus temperatures up to 2000 °C were studied in terms of liquid–solid regions, transformations, and decompositions, with varying process conditions

A zone melting device for the in situ observation of directional solidification using high-energy synchrotron x rays

Directional solidification (DS) is an established manufacturing process to produce high-performance components from metallic materialswith optimized properties. Materials for demanding high-temperature applications, for instance in the energy generation and aircraft enginetechnology, can only be successfully produced using methods such as directional solidification. It has been applied on an industrial scalefor a considerable amount of time, but advancing this method beyond the current applications is still challenging and almost exclusivelylimited to post-process characterization of the developed microstructures. For a knowledge-based advancement and a contribution to materialinnovation, in situ studies of the DS process are crucial using realistic sample sizes to ensure scalability of the results to industrial sizes.Therefore, a specially designed Flexible Directional Solidification (FlexiDS) device was developed for use at the P07 High Energy MaterialsScience beamline at PETRA III (Deutsches Elektronen–Synchrotron, Hamburg, Germany). In general, the process conditions of the cruciblefree,inductively heated FlexiDS device can be varied from 6 mm/h to 12 000 mm/h (vertical withdrawal rate) and from 0 rpm to 35 rpm(axial sample rotation). Moreover, different atmospheres such as Ar, N2, and vacuum can be used during operation. The device is designedfor maximum operation temperatures of 2200 ○C. This unique device allows in situ examination of the directional solidification process andsubsequent solid-state reactions by x-ray diffraction in the transmission mode. Within this project, different structural intermetallic alloyswith liquidus temperatures up to 2000 °C were studied in terms of liquid–solid regions, transformations, and decompositions, with varyingprocess conditions