Hot isostatic pressing of Cu-15Ni-8Sn alloy with suppressed Sn macro-segregation and enhanced mechanical properties

摘要

Sn macro-segregation and coarse grains easily occur in the conventional casting process of the Cu-15Ni-8Sn alloy with a high Sn content. Here, hot isostatic pressing (HIP), an advanced powder metallurgy technique, was introduced to explore feasibility in alleviating or eliminating such defects. The gas-atomized powder with high homogeneity of composition was used, which was solidified rapidly. The microstructural evolution, mechanical properties, deformation mechanisms and strengthening mechanisms were deeply and systematically revealed and discussed. Nearly fully dense samples were fabricated by HIP with no Sn macro-segregation, and simulta-neous strength-plasticity enhancement was obtained. The content of harmful discontinuous precipitation col-onies was controlled to only-3.11 vol%. This was attributed to the fine grain size of the powder and the preferential complete recrystallization process during the HIP. That is, the gamma nucleation sites were occupied by numerous grain boundaries provided by fine grains, and the driving force of gamma growth was consumed by recrystallization. Furthermore, enhanced mechanical properties were related to the Sn macro-segregation sup-pression, grain refinement (-11.0 mu m), dislocation density continuous increase, and dispersion distribution of gamma precipitates, etc. These encouraging findings validate the advantages and potential of HIP in the fabrication of Cu-15Ni-8Sn alloy with enhanced mechanical properties for structural applications.

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