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Nanoscale solute partitioning across multiple constituent phases in a 980-grade quenched and partitioned (Q&P) steel was analyzed using atom probe tomography (APT). The Q&P process was used to increase the C content in the retained austenite phase thereby improving its stability under plastic straining. Significant carbon enrichment of austenite was measured with decreased levels of C in martensite...
Characterization of the bulk microstructure using neutron diffraction has been applied to investigate the phase fractions and textures of α- and β-phases in Ti-6Al-4V fabricated by additive manufacturing. The microstructure of a specimen cut from a fan structure, built by either electron beam melting (EBM) or selective laser melting, indicated that predominantly the build direction and not the fan...
A two-color pyrometer is aligned co-axially to the laser inside a Laser Engineered Net Shaping machine to gather thermal data during a single layer two-pass deposit. Several molten pool metrics are calculated from the pyrometer data, and anomalies in the data are used to flag potential defect locations. The depositions are scanned using x-ray Computed Tomography (XCT) with a 4.13 micron voxel, and...
Oxygen is always a constituent in “real” titanium alloys including titanium alloy powders used for powder-based additive manufacturing (AM). In addition, oxygen uptake during powder handling and printing is hard to control and, hence, it is important to understand and predict how oxygen is affecting the microstructure. Therefore, oxygen is included in the evaluation of the thermodynamic properties...
Ti-6Al-4V is the most studied alloy via electron beam melting (EBM) with regards to microstructure and mechanical behavior, but there have been no attempts to correlate in situ porosity detection and fatigue behavior. This is required for widespread adoption of EBM because conventional evaluation is often time-consuming and expensive. This paper presents the use of near-infrared imaging to detect...
Powder bed fusion (PBF) of titanium alloys is an interesting manufacturing route for many applications requiring light weight and strength combined with geometric complexity. Managing PBF challenges, including porosity, surface finish, distortions and residual stresses of as-built material, is mandatory to bring the advantages of this process to production main stream. This paper builds on previous...
Cost control and quality of additive manufactured (AM) components are critical characteristics for the success of this technology for industrial applications. Understanding how the virgin powder changes in terms of chemistry and physical properties with reuse cycles provides important information that can be translated into cost-effective practices for managing recycled powder. In this study, we focused...
Additive manufacturing (AM) enables a fabrication freedom and is transforming the manner in which high-value and high-performance structures are created. The aerospace industry stands to benefit from structures in which the weight is minimized, the materials provide good mechanical properties at extreme temperatures, and a swarm of distinct parts can be consolidated into a single non-assembled complex...
Hybrid manufacturing (HM), which integrates additive and subtractive manufacturing in one system, has become a popular choice for near-net-shape fabrication of complex parts. Although HM systems have been investigated for decades with major efforts on hardware and motion control system development, less work has been done in the exploration of relationships between microstructure evolution and the...
Intricate metal lattice structures enabled by additive manufacturing (AM) are finding increasing applications. We report a detailed study of the manufacturability of Ti-6Al-4V lattice struts by selective electron beam manufacturing (SEBM). A total of 165 strut samples with design diameters of 0.05–3.0 mm are manufactured at 11 different inclination angles from 0° to 90°. The discrepancies between...
Nature-inspired processing of complex reticular/cellular architected materials by selectively incorporating multiphase materials in emulsions with targeted interactions is reported in this work. In particular, structuring of TiO2 foams at different scales is realized by combining colloidal processing and 3D printing with fundamental understanding of the TiO2 nanoparticle system. Specifically, hybrid...
A new atom probe design is presented along with data showing spectral performance and selected microstructural characterization examples. The instrument includes a curved reflectron, a 532-nm laser, and an integrated, fixed-position, counter electrode in a configuration with moderate electric field enhancement that includes improvements in ease of use and cost of ownership. Both voltage-pulsed and...
We report on the impact of laser processing on material and device performance characteristics for integrated energy applications. A femtosecond laser was used for development of flexible and transparent supercapacitors, while a nanosecond laser was successfully exploited for high-performance Al–air battery development. A laser direct-write process enabled integration of a three-dimensional-structured...
Carbon is a powerful alloying element for titanium alloys. In this work, trace carbon is alloyed with Ti-6Al-4V during wire + arc additive manufacturing, and the effects on the solidification process, microstructure and mechanical properties are explored. With between 0.03 wt.% and 0.41 wt.% carbon, the prior-β grain size and α-lath length reduce by factors of 5–6 which is attributed to separate grain...
Control of the bath’s composition and temperature is crucial to the stability, energy consumption and material efficiency of the aluminium electrolysis process. The traditional approach involves periodic measurement of the bath’s composition with x-ray diffraction, as well as the bath’s temperature. The sampling and corrective measures applied to the cell can take 8–12 h. Since the relationship between...
The possibility of predicting the fatigue behavior of additively manufactured materials by means of microstructure- and defect-sensitive models is discussed in this paper. The effects of surface roughness, process-induced defects, and microstructure on the fatigue life of additively manufactured materials are presented, along with discussions on efforts to incorporate the subsequent effects of these...
To reveal the influence of hydrogen on the characteristics of defect-free titanium alloy welded joints, the effects of hydrogen addition on the precipitation behavior in the hydrogenated 0.12 wt.%H weld zone of Ti-0.3Mo-0.8Ni alloy argon-arc-welded joints have been investigated. The results showed that lamellar δ-hydride (face-centered cubic) could only precipitate from α-lamellae, but not from the...
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