Phase control in immiscible Zn-Bi alloy by tungsten nanoparticles

• W nanoparticles were used in Zn-Bi melt for phase control during solidification.
• This approach significantly refined the microstructure and avoid sedimentation.
• The good wettability between W and melt simplify the nanocomposites processing.
• This new process has great potential for scale-up manufacturing immiscible alloys.

Immiscible Zn-Bi alloy has a good potential to replace lead-based alloys to serve as a running layer in plain bearings. However, it is still a major challenge to uniformly disperse Bi phase in Zn matrix during solidification processing since Bi droplets grow very fast in liquid state and readily coagulate to induce phase sedimentation. In this study, tungsten (W) nanoparticles were, for the first time, used and effectively incorporated into the Zn-Bi melt for phase control. Tungsten nanoparticles were able to self-assemble onto the Zn-Bi phase interfaces to slow down the growth of the Bi phase and prevent their coagulations, resulting in a significant size reduction of the Bi phase and microstructure refinement. Moreover, the incorporation of W nanoparticles into the Zn-Bi alloy enhanced its microhardness significantly. This new approach of using chemically-stable metal nanoparticles has a great potential for scale-up manufacturing of immiscible alloys for widespread applications.

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