Gloria Graf

Bio: Gloria Graf is an academic researcher from University of Leoben. The author has contributed to research in topics: Materials science & Alloy. The author has an hindex of 1, co-authored 2 publications receiving 2 citations.

Revealing dynamic processes in laser powder bed fusion with in situ X-ray diffraction at PETRA III.

Abstract: The high flux combined with the high energy of the monochromatic synchrotron radiation available at modern synchrotron facilities offers vast possibilities for fundamental research on metal processing technologies. Especially in the case of laser powder bed fusion (LPBF), an additive manufacturing technology for the manufacturing of complex-shaped metallic parts, in situ methods are necessary to understand the highly dynamic thermal, mechanical, and metallurgical processes involved in the creation of the parts. At PETRA III, Deutsches Elektronen-Synchrotron, a customized LPBF system featuring all essential functions of an industrial LPBF system, is used for in situ x-ray diffraction research. Three use cases with different experimental setups and research questions are presented to demonstrate research opportunities. First, the influence of substrate pre-heating and a complex scan pattern on the strain and internal stress progression during the manufacturing of Inconel 625 parts is investigated. Second, a study on the nickel-base superalloy CMSX-4 reveals the formation and dissolution of γ' precipitates depending on the scan pattern in different part locations. Third, phase transitions during melting and solidification of an intermetallic γ-TiAl based alloy are examined, and the advantages of using thin platelet-shaped specimens to resolve the phase components are discussed. The presented cases give an overview of in situ x-ray diffraction experiments at PETRA III for research on the LPBF technology and provide information on specific experimental procedures.

Microstructure and mechanical properties of a structurally refined Al–Mg–Si alloy for wire-arc additive manufacturing

Abstract: Wide-spread utilization of wire-arc additive manufacturing (WAAM) technologies require the development of high-performance aluminum alloys with a robust processing window. Suitable alloys have to be modified to reduce their susceptibility for hot cracking - a common means is grain refinement via inoculation. Here, an advanced Al–Mg–Si alloy with a TiB 2 containing structural refiner is processed using WAAM. As a result, no macroscopic cracks are observed in the deposit. The microstructure consists of fine (<30 μm) and equiaxed grains that do not show any crystallographic texture. Both characteristics are considered to result from preferential heterogeneous nucleation yielding a reduced tendency for epitaxial nucleation. No coarsening of the heterogeneous nucleants is observed when comparing wire and WAAM deposit microstructures. After a two-step heat treatment, where negligible grain coarsening is observed during the solution heat treatment, the yield strength reaches ∼ 265 MPa irrespectively of the tensile direction. Gained results provide the basis for the application of an advanced Al–Mg–Si alloy using the WAAM technology. • Theoretic concepts of grain refinement revisited. • WAAM processing of a structurally refined Al–Mg–Si alloy yields crack-free specimens. • Microstructure consists of fine (<30 μm), equiaxed grains. • No crystallographic texture present resulting in isotropic yield strength. • Yield strength of ∼ 265 MPa achieved via a two-step heat treatment.

Microstructure and mechanical properties of a structurally refined Al–Mg–Si alloy for wire-arc additive manufacturing

Abstract: Wide-spread utilization of wire-arc additive manufacturing (WAAM) technologies require the development of high-performance aluminum alloys with a robust processing window. Suitable alloys have to be modified to reduce their susceptibility for hot cracking - a common means is grain refinement via inoculation. Here, an advanced Al–Mg–Si alloy with a TiB2 containing structural refiner is processed using WAAM. As a result, no macroscopic cracks are observed in the deposit. The microstructure consists of fine (