Ultrasonic additive manufacturing (UAM) is a solid state manufacturing process that combines additive joining of thin metal tapes and subtractive computer numerical control milling operations to generate near-net shape metallic parts. We conducted a design of experiments study with the goal to optimize UAM process parameters for aluminum 6061. Weld force, weld speed, amplitude, and temperature were varied based on a Taguchi L18 experimental design matrix and tested for mechanical strength using a shear test and a comparative push-pin test. Statistical methods including analysis of variance (ANOVA), mean effects plots, and interaction effects plots were conducted to determine optimal process parameters. Results indicate that weld amplitudes of 32.76 µm and weld speeds of 84.6 mm/s yield maximum mechanical strength while temperature and force are statistically insignificant for the parameter levels tested. Annealing of cold-worked foil stock produces a 13% strength increase for UAM samples over homogeneous annealed material.

An additive layer manufacturing (ALM) process based on gas tungsten arc welding (GTAW) was used to produce simple 3-dimensional titanium aluminide components, which were successfully in situ alloyed by separately delivering elemental Al and Ti wires to the weld pool. The difference in microstructure, chemical composition, and microhardness of four wall components built with four different wire-feeding conditions has been evaluated. There was no significant change in the microstructure of the four walls. The composition and microhardness values were comparatively homogeneous throughout each wall except the near-substrate zone. However, with increasing the ratio of Al to Ti wire feed rates from 0.80 to 1.30, an increase of Al concentration and γ phases were observed. The situation was reversed for the effect of the Al:Ti ratio on microhardness. Additionally, an unexpected increase in the α2 phase was produced when the ratio was increased to 1.30.

Materials produced by selective laser melting (SLM) experience a thermal history that is markedly different from that encountered by conventionally produced materials. In particular, a very high cooling rate from the melt is combined with cyclical reheating upon deposition of subsequent layers. Using atom-probe tomography (APT), we investigated how this nonconventional thermal history influences the phase-transformation behavior of maraging steels (Fe–18Ni–9Co–3.4Mo–1.2Ti) produced by SLM. We found that despite the “intrinsic heat treatment” and the known propensity of maraging steels for rapid clustering and precipitation, the material does not show any sign of phase transformation in the as-produced state. Upon aging, three different types of precipitates, namely (Fe,Ni,Co)3(Ti,Mo), (Fe,Ni,Co)3(Mo,Ti), and (Fe,Ni,Co)7Mo6 (µ phase), were observed as well as martensite-to-austenite reversion around regions of the retained austenite. The concentration of the newly formed phases as quantified by APT closely matches thermodynamic equilibrium calculations.

High Speed Sintering (HSS) is a novel additive manufacturing technology which currently uses Nylon 12 as the standard feedstock material. To expand the number of processable materials, the preferred characteristics of polymeric powder as a feedstock powder are presented, appropriate materials identified, parts made, and mechanical properties measured. Two commercially available laser sintering (LS) grade powders previously untested for HSS were selected, DuraForm® HST10 and ALM TPE 210-S. Tensile test specimens were manufactured using each material and mechanical properties analyzed and compared to the manufacturers' specification for LS. Tensile test specimens built using DuraForm® PA show higher tensile strength and elongation at break than LS whereas DuraForm® HST10 shows somewhat reduced tensile strength but slightly increased elongation at break. ALM TPE 210-S shows elongation at break of more than double that of LS demonstrating the capability of HSS to process viscous materials. The results indicate that HSS is capable of processing LS grade polymeric powders and may extend beyond.

Laser additive manufacturing allows the production of polymeric or metallic parts with complex shapes. A major advantage of this contactless technology is that it allows reaching very high energy densities with an excellent precision in short times. This is very suitable for processing hard refractory metals for instance. Unfortunately, current results are less satisfactory for ceramics as a consequence of their intrinsic properties such as a low thermal shock resistance and very high refractoriness. Another significant limitation is related to the poor absorptivity of oxide ceramics in the near-infrared region which is typical for most commercial selective laser melting (SLM) machines. This study considers an alternative to overcome the above-mentioned limitations, especially the lack of absorptivity. SLM of oxide ceramics has become possible. Large parts with complex shapes and relative densities up to 90% have been manufactured on a commercial SLM machine.

The present study is dealing with the basic physics for a novel way to generate a free-formed ceramic body, not like common layer by layer, but directly by Selective Volume Sintering (SVS) in a compact block of ceramic powder. To penetrate with laser light into the volume of a ceramic powder compact it is necessary to investigate the light scattering properties of ceramic powders. Compared with polymers and metals, ceramic materials are unique as they offer a wide optical window of transparency. The optical window typically ranges from below 0.3 up to 5 µm wave length. In the present study thin layers of quartz glass (SiO2) particles have been prepared. As a function of layer thickness and the particle size, transmission and reflection spectra in a wave length range between 0.5 and 2.5 µm have been recorded. Depending on the respective particle size and by choosing a proper relation between particle size and wave length of the incident laser radiation, it is found that light can penetrate a powder compact up to a depth of a few millimeters. With an adjustment of the light absorption properties of the compact the initiation of sintering in the volume of the compact is possible.

This work describes the use of a piezo-actuated inkjet print head with a nozzle aperture of 50 µm to obtain picoliter drops of different model ionic liquids (ILs). A theoretical analysis of the microdrop generation of three model ILs is confirmed by experiments. The inkjet print process was optimized to enable a stable and reproducible drop ejection in both continuous and drop-on-demand modes by controlling the temperature of the nozzle, as well as the electrical signal sent to the piezo actuator used to generate the drops. Controlled volumes ranging from 43 ± 3 pL to 319 ± 1 pL have been achieved, with a volume control down to 3 pL. The null volatility of ILs yields an extremely high stability of the inkjet process, obtaining drops with very constant volumes during the entire print process. It also avoids the coffee staining effect observed in the deposition of conventional liquid drops. The possibility to deposit controlled volumes in a reproducible way is demonstrated here and applied to a proof-of-concept application with the aim to create dense concave optical lens arrays by replicating the deposited ionic liquid microdrops in poly(dimethylsiloxane) (PDMS).