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Selective laser sintering (SLS) is a rapidly developing additive manufacturing technique, with advantages in flexibility and low material waste. Many parameters used in a SLS process are determined by powder type: blended powders have limitations due to wetting and diffusion, while prealloyed powders require processing in a small temperature range dictated by the alloy composition. As an alternative to these, a coated powder was fabricated by electrochemical means. This tin-copper composite powder was compared with a blend of tin and copper powders, using metallographic, crystallographic, and thermal analysis techniques as well as SLS. It was found that, because of the uniform distribution of liquid and increased contact between phases in the composite powder, sintering took place in the composite powder but not in the blend. After a homogenization treatment, mechanical testing of the sintered samples showed that the strength and ductility were comparable to high-porosity materials produced using other techniques.

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Historically, the production of metallic components for the automotive and aerospace industries has been dominated by wrought and ingot metallurgy metal forming practices. These technologies offer considerable design flexibility to engineers and are readily amenable to ferrous and nonferrous alloys alike. However, in applications that require precise dimensional control, the tolerances attainable are generally inadequate. This represents a formidable limitation and mandates the incorporation of expensive secondary machining. Furthermore, because these processes are carried out under conditions that approach those of equilibrium, these technologies are also faced with rather strict limitations on the range of alloy chemistries that can be employed. As the demands for improved material performance and process economics increase, the aforementioned shortcomings become increasingly important. Consequently, considerable attention has and continues to be focused on alternate metal forming techniques such as powder metallurgy (P/M). Using the P/M approach, dimensional tolerances are commonly improved by one to two orders of magnitude and alloy chemistry limitations are essentially eliminated. The work described herein provides an overview of select P/M techniques developed by the authors, initially to enhance the hardness and tensile properties of aluminum-based P/M alloys through a mineral dissociation/diffusion process. This is expanded through alloy development research wherein a P/M processing route designed to simulate industrial practices is used in the most recent work based on the effects of rare earth additions on selected mechanical properties of aluminum P/M alloys. These results include a compilation of theoretical calculations (thermodynamics and diffusion rates) that are supported by experimental data using techniques that include electron microprobe analyses, X-ray diffraction, tensile testing, and wear testing. Specific findings are that minerals/compounds such as wollastonite and silver nitrate can be successfully reacted to enhance selected mechanical properties of aluminum P/M alloys and that wear resistance may be improved through a P/M approach applied to AA2014.

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