Development of Innovative Aluminum Powder Metallurgy (PM) Alloys Utilizing Hybrid Alloying Technology

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The focus of this proposal is aluminum powder metallurgy (PM) processing. This is an emerging near-net-shape metal forming technology wherein aluminum-based powders (and powdered forms of the desired alloying additions) are directly manipulated into geometrically complex components through a sequence of powder compaction, liquid phase sintering, and secondary operations such as heat treatment. Aluminum PM has advanced steadily in recent years principally through the development of new alloys that exhibit a high sintered density (>99%) and in turn, significant improvements in ambient mechanical properties relative to the out dated conventional blends now in use for over 40 years. While the next generation materials open many new applications for aluminum PM processing, new challenges have arisen as well. The most prolific is their propensity for non-uniform shrinkage during sintering. Coming as a result of the intense densification behaviour, it yields distorted sintered products and greatly diminishes the near-net-shape advantage upon which aluminum PM is built. To mitigate the distortion dilemma, the applicant recently designed a concept deemed "hybrid alloying" whereby the sintering particles of aluminum would be strengthened by the addition of a small amount of prealloyed zirconium. This element has a slow diffusion rate in aluminum and forms a refined distribution of Al3Zr particles that are hard, exceptionally fine ((<20nm), thermodynamically stable, and highly resistant to thermal coarsening - attributes that enable the aluminide particles to act as efficient strengthening features throughout the complete sintering cycle. Research on the concept has been restricted to a single base alloy and dilute concentrations of Zr to date yet the results are highly promising and imply that a much broader scope of opportunities exists for the technique. Thus, the objective of this proposal is to expand research on hybrid alloying to maximize the likelihood of widespread commercial adaptation. Activities will address an enhanced fundamental understanding, chemical refinements, the use of hybrid alloying in an array of alloys, and mechanical testing.