Papers by Keyword: EBSD

Abstract: Additive manufacturing by laser powder bed fusion (LPBF) is increasingly applied to aluminium alloys; however, the resulting surface quality and machining behaviour remain critical challenges, particularly when post-processing is required. In this context, the interaction between LPBF process parameters and advanced cooling strategies during machining remains largely unexplored.This study examines the impact of cryogenic machining on the surface integrity of LPBF-produced AlSi7Mg components, fabricated with varying layer thicknesses. Specimens were machined under fixed cutting parameters using either conventional flood cooling or cryogenic cooling. Cutting forces, surface roughness, defect morphology, and subsurface microstructure were systematically evaluated.Cryogenic cooling consistently reduced cutting forces and improved surface quality, effectively suppressing tearing formation. In contrast, under flood cooling, the influence of the microstructural differences induced by layer thickness remained significant, with increasing LPBF layer thickness further enhancing both surface and subsurface integrity. Overall, the results reveal a strong interaction between LPBF parameters and cooling strategy, highlighting the unexpectedly beneficial role of cryogenic machining in improving the surface integrity of LPBF-processed AlSi7Mg alloys.

Abstract: The present study aims to investigate the anisotropic creep behaviour of aluminium alloy 2139 during artificial ageing, through in situ thermomechanical loadings under Electron Backscattered Diffraction (EBSD). EBSD analysis enabled the characterisation of microstructural parameters and the identification of grain misorientations which were further correlated with macroscopic creep strain. In situ analyses were conducted within a Scanning Electron Microscope (SEM) using a micro‑tensile stage that allows simultaneous heating and mechanical loading. Creep tests were performed at 160°C under 50, 100 and 150 MPa along three different orientations in order to investigate the creep behaviour of the alloy. Kernel Average Misorientation (KAM) maps showed a progressive increase of the average KAM values for the different loading conditions, reaching a saturation value after 10 hours. Ex situ tensile tests were conducted on creep‑aged specimens using Digital Image Correlation (DIC). The main mechanical property evolutions (averaged across all orientations) are a 45 % increase in yield stress, a 10 % increase in ultimate tensile stress and a reduction in ductility, characterised by a notable decrease in elongation. Further works will focus on the result repeatability, as well as on the influence of prior deformation on the creep strain.

Abstract: Steel 22MnB5 is widely used in the automotive industry for manufacturing high-strength structural car body parts. To achieve desired mechanical properties, hot-stamping is used, during which the Al-Si coating plays a critical protective role against oxidation. This study investigates the structural evolution of the Al-Si coating under various austenitization durations at 920 °C. Intermetallic phase formation and coating morphology are analyzed.

Abstract: The design flexibility afforded by additive manufacturing, commonly known as 3D printing, is broadening the industrial applications of high-entropy alloys (HEAs). The 3D-printed CrMnFeCoNi HEA (or Cantor alloy) exhibits a unique combination of strength and ductility, attributed to its multifaceted deformation mechanisms. While the deformation behavior of this alloy under monotonic loading has been extensively studied, its cyclic plasticity, which is crucial for fatigue performance, remains a relatively underexplored area. To address this gap, the current work investigates the deformation microstructure of a CrMnFeCoNi HEA fabricated using laser-beam powder bed fusion. Electron backscatter diffraction (EBSD) is employed to characterize the surface microstructural changes. The results reveal the simultaneous activation of multiple slip systems in the region near the fatigue crack, which induces grain rotation. Additionally, the activation of twinning-induced plasticity plays a significant role in accommodating the cyclic plastic strain.

Abstract: The present study aims to investigate the mechanical behaviour of pure cobalt in plasticity at varying temperatures, through in situ thermomechanical loadings under Electron Backscattered Diffraction (EBSD) in order to gain a deeper understanding of the various mechanisms that occur. EBSD analysis allows for the determination of microstructural parameters at a refined scale including grain size, grain misorientation, crystallographic and morphologic texture, and phase ratios, which can be employed to establish a correlation between microstructural changes and deformation mechanisms with temperature. Analyses were conducted in situ using either a furnace that can reach 1000 °C, or a 10 kN thermomechanical device, which enables simultaneous heating and mechanical loading. Both test types were automated in the Scanning Electron Microscope (SEM) by correlating the stage movement with the region of interest, enabling EBSD mappings to be acquired always at the same location. Mappings were post-processed via the spherical indexing process, which yields high-quality indexation (with a reduced number of points exhibiting a Confidence Index of less than 0.1), even at high strain levels. Such experiments conducted on cobalt demonstrated austenitic and martensitic transformations between hexagonal close packed and face centred cubic phases with temperature. Indeed, approximately 31.6 % of the initial face centred cubic phase has transformed into the hexagonal phase for 8 % strain during an in situ tensile test. This transformation is initiated in plasticity by dislocation motions in basal planes and subsequently accelerated by the concurrent activation of mechanical twinning. Additionally, an in situ thermal treatment in the SEM enabled the accurate determination of the phase transformation temperature: 460 °C during heating and 350 °C during cooling, corresponding to the points where the cubic phase fraction reaches a 50 % relative change.

Abstract: Fatigue crack generation and propagation processes in oxygen-free copper for power equipment were investigated in a time series to search for new parameters that indicate the fatigue damage degree. The damage behavior of crystal grains was observed by optical microscopy, electron backscattered diffraction (EBSD) analysis and elastic strain analysis. The obtained results suggest that the change in grain orientation spread (GOS) and grain average misorientation (GAM) values is possible to detect the fatigue crack generation. Moreover, it was found that the change in the plastic strain range is also possible to detect it.

Abstract: To generate both two-dimensional electron gas (2DEG) and two-dimensional hole gas (2DHG) at will in SiC polytype heterojunctions, simultaneous lateral epitaxy (SLE) method has been extended to form epilayers of alternating stacks of 4H-and 3C-SiC, which includes the first formation of single-domain 4H-SiC on 3C-SiC. The process starts with a spontaneous generation of mononuclear 3C-SiC on the atomically flat wide terrace on 4H-SiC, which expands parallel to the basal plane to form a single-domain 3C-SiC layer having the coherent interface with the underlying 4H-SiC layer. Step-controlled epitaxy is then applied using the adjacent 4H-SiC steps to grow an alternative 4H-SiC layer on top of the 3C-SiC surface, forming another coherent interface. The crystal structure, the interface structure, and the carrier distribution of this stacked epilayers was analyzed. Finally, it is demonstrated that 2DEG occurs at the coherent interface between the 3C-SiC Si-and 4H-SiC C-faces and 2DHG at the 3C-SiC C-and 4H-SiC Si-faces.

Abstract: The layer structure of 3C-SiC stacked on 4H-SiC is implemented by simultaneous lateral epitaxy (SLE). The SLE, involving spontaneous nucleation of 3C-SiC(111) on the 4H-SiC(0001) surface followed by step-controlled epitaxy, facilitates the creation of a single-domain 3C-SiC layer with an epitaxial relationship to the underlying 4H-SiC, establishing a coherent (111)//(0001) interface aligned in the basal plane. An extremely low state density at an interface between thermally grown SiO₂ and SLE-grown 3C-SiC layer is revealed by local deep level transient spectroscopy (local-DLTS) based on scanning nonlinear dielectric microscopy (SNDM).

Abstract: Austempered Ductile Irons is a promising material with a favorable combination of low price and good mechanical properties. It is produced by isothermal hardening of cast iron with nodular graphite. The heat treatment parameters directly influence the structure of the matrix. The structure consists of an ausferrite matrix - a mixture of epitaxial ferrite + residual austenite and graphite. The resulting mechanical properties depend on the proportion and morphology of the individual phases. Therefore, a thorough structural characterisation is needed to describe the influence of the heat treatment parameters. However, conventional methods such as optical microscopy do not provide sufficient accuracy. Therefore, this work used a very accurate EBSD method to evaluate the structure in the as-received state and after heat treatment.

Abstract: The most common titanium alloy used in combination with additive manufacturing is Ti-6Al-4V ELI. On the other hand, the 3D printing of β-Ti alloys is still in the stage of development of both materials and their treatment. The newly developed biomedical Ti alloys are often containing Nb, Ta, Zr. These alloys are showing very good values in terms of biocompatibility and corrosion resistance while their elastic modulus may be in the range of 30-70 GPa. The printing of these alloys is however limited by their relative novelty. Powders are not yet available through traditional commercial ways. In this work, Ti–24Nb–8Ta–4Sn specimens prepared by the selective laser melting (SLM) method were used. The porosity was evaluated by two methods: area porosity evaluated by image analysis on metallographic specimens and volume porosity evaluated by micro-computed tomography (μCT). The microstructure was observed using both light and scanning electron microscopy (SEM). The SEM was as well used for energy dispersive spectroscopy (EDS) for chemical analysis and the analysis of crystallographic orientation was conducted using the method of electron backscattered diffraction (EBSD).