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

Abstract

Directional solidification (DS) is an established manufacturing process to produce highperformance components from metallic materials with optimized properties. Materials for demanding high-temperature applications, for instance in 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 (HEMS) beamline at PETRA III (Deutsches Elektronen-Synchrotron (DESY); Hamburg, Germany). In general, the process conditions of the crucible-free, inductively heated FlexiDS device can be varied from 6 to 12000 mm/h (vertical withdrawal rate) and from 0 to 35 rpm (axial sample rotation).Moreover, different atmospheres like Ar, N2, 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 Xray 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.

In situ Observation of Ternary Eutectic Growth in a Directionally Solidified Mo–Si–B Alloy Using High‐Energy Synchrotron X‐Rays

“…A DS process was observed in situ with high‐energy X‐ray synchrotron measurements to study the growth behavior at the liquid–solid transition of a multicomponent alloy. To carry out these experiments, a new and unique sample environment “FlexiDS” [ 24 ] had been used to directly investigate crystal growth of the ternary eutectic Mo–Si–B alloys. Prior to DS, the eutectic alloy Mo–17.5Si–8B was prepared via arc‐melting and cold crucible casting.…”

“…DS was carried out using the FlexiDS zone melting device, [ 24 ] a worldwide unique sample environment that was specially designed to be used for DS in situ experiments at the P07 High Energy Materials Science (HEMS) beamline operated by Helmholtz‐Zentrum Geesthacht at PETRA III (DESY; Hamburg, Germany). In this work, DS was carried out in an Ar atmosphere using a growth velocity of 60 mm h −1 and a synchronized rotation speed of 20 rpm for the feed and seed axis.…”

“…[12,17] It has to be noted here, that the FlexiDS device uses two pyrometers for process control during directionally growth. [24] However, the positions are fixed within the induction coil (liquid zone) and at 10 mm above the coil and are, thus, not linked to the coordinate system of the positioning stage that moves the whole device up and down relative to the synchrotron X-ray beam. Hence, the increasing/decreasing volume fraction of the liquid phase was taken as a first indicator for the temperature in within the ternary Mo SS -Mo 3 Si-Mo 5 SiB 2 eutectic and it is cubic, thus only one lattice parameter "a" has to be tracked.…”

An In Situ High‐Energy Synchrotron X‐Ray Diffraction Study of Directional Solidification in Binary TiAl Alloys

“…These rods were used for the directional solidification experiments in the abovementioned zone‐melting device. [ 22 ] In the zone‐melting furnace, the cylindrical specimens are held by water‐cooled chucks and heated by an induction coil (150–375 kHz, max. heating power of 12 kW, maximum temperature of 2200 °C) in a zone of about 1 cm length.…”

“…By high‐energy X‐ray diffraction as supplied by a storage ring X‐ray source, macroscopic TiAl specimens can easily be investigated in transmission, and the crystal structure and growth orientation of solidifying phases can be identified. In the present work, a crucible‐free, inductively heated zone‐melting device, that has been designed for in situ studies with a synchrotron radiation beam, has been used [ 22 ] to study solidification modes under varying solidification conditions. This so‐called FlexiDS device allows to investigate materials via diffraction with the liquidus temperatures of up to 2200 °C and the diameters of up to 14 mm.…”