No abstract

With recent advancements in additive manufacturing (AM) technology, it is possible to deposit copper conductive paths and insulation layers of an electric machine in a selective controlled manner. AM of copper enables higher fill factors that improves the internal thermal conduction in the stator core of the electric machine (induction motor), which will enhance its efficiency and power density. This will reduce the motor size and weight and make it more suitable for aerospace and electric vehicle applications, while reducing/eliminating the rare-earth dependency. The objective of this paper is to present the challenges associated with AM of copper coils having 1 × 1 mm cross section and complex features that are used in producing ultra-high efficiency induction motor for traction applications. The paper also proposes different approaches that were used by the authors in attempts to overcome those challenges. The results of the developed technologies illustrate the important of copper powder treatment to help in flowing the powder easier during deposition. In addition, the treated powder has higher resistance to surface oxidation, which led to a high reduction in porosity formation and improved the quality of the copper deposits. The laser powder direct energy deposition (LPDED) process modeling approach helps in optimizing the powder deposition path, the laser power, and feed rate that allow the production of porosity free thin wall and thin floor components. The laser powder bed fusion (LPBF) models identify the optimum process parameters that are used to produce test specimens with >90% density and minimum porosity.

Nanocomposites of MgO with Y2O3 have been produced from the respective nitrates by an esterification reaction with ethylene glycol and citric acid. The evolution of nitrous oxides during the reaction causes the product to foam, and the calcination of this foam gives nanocomposite powders with extremely fine, uniform grains, and phase domains. These microstructures are remarkably stable both under postcalcination heat treatment and during consolidation by hot pressing. These stable microstructures arise as a result of the decomposition sequence: this involves the formation of a metastable amorphous/vitreous intermediate followed by concurrent crystallization and phase separation on the nanoscale.

A sucrose‐mediated aqueous sol–gel procedure was developed to synthesize MgO–Y2O3 nanocomposite ceramics for potential optical applications. The synthesis involves the generation of a precursor foam containing Mg2+ and Y3+ cations via the chemical and thermal degradation of sucrose molecules in aqueous solution. Subsequent calcination and crushing of the foam gave MgO–Y2O3 nanocomposites in the form of thin mesoporous flake‐like powder particles with uniform composition and surface areas of 27–85 m2 g−1, depending on calcination conditions. The flakes exhibited a homogeneous microstructure comprising intimately mixed nanoscale grains of the cubic MgO and Y2O3 phases. This microstructure was resistant to grain coarsening with average grain sizes of less than 100 nm for calcination temperatures of up to 1200°C. The results indicate that the sucrose‐mediated sol–gel process is a simple effective method for making nanoscale mixed oxides.

Accelerated cabinet style corrosion tests are developed to determine the susceptibility of metals to specific types of corrosion such as pitting, intergranular corrosion (IGC), and exfoliation. However, this work shows that not all tests result in an accurate representation of the corrosion attack found in long-term outdoor exposures at both industrial and sea coast locations. This is particularly true for the thirdgeneration Al-Li alloy 2070. To better understand the propensity of Al-Li alloys to particular forms of corrosion attack in various exposure environments, the corrosion morphology and extent of attack for AA7075-T6 and AA2070 in several tempers are compared between laboratory-accelerated cabinet and outdoor corrosion tests. The variation in the corrosion type of attack and depth as determined using crosssectional analysis and white light interferometry is discussed. Results show severe exfoliation on AA7075-T6 after an accelerated ASTM G34 (EXCO) test while ASTM B117 testing reveals pitting. For AA2070, it was observed that the corrosion morphology varied by temper after the ASTM G85-A2 accelerated test, where the underaged AA2070-T3 exhibited both IGC and grain lifting, and peak aged and overaged AA2070 exhibited pitting. Results suggest that the ASTM G85-A2 dry bottom modified ASTM acetic acid salt intermittent spray test correlates better with outdoor seacoast and industrial exposures than either ASTM B117 or EXCO.