Chemical inertness and thermal shock resistance of ZrN/AlN composites for TiNi alloy induction melting

Abstract

TiNi alloys with excellent mechanical properties and unique functional characteristics show substantial potential for producing engineered structural components and biomedical materials. However, the high reactivity of molten TiNi poses significant challenges when ceramic crucibles are used in vacuum induction melting, inevitably resulting in severe ingot contamination. In this study, we report an innovative method for producing high-purity, low-contamination TiNi ingots by using a ZrN/AlN composite ceramic crucible. Fundamentally, this ZrN/AlN composite crucible fabricated with vacuum pressureless sintering technology, is characterized by its high relative density (>95 %) and absence of cracks. The ZrN/AlN composites exhibit impressive properties, including excellent flexural strength, high thermal conductivity, and exceptional thermal shock resistance. Notably, during induction melting, the crucible surface forms a dense TiN barrier layer, thereby protecting the crucible substrate. Compared with traditional oxide refractories, the as-prepared ingots have a low interstitial atom content (Wt. (O, N) < 1000 ppm), demonstrating the superior corrosion resistance of the ZrN/AlN composite crucible. This work provides a comprehensive understanding of crucible-melt interaction mechanisms and a promising method for producing high-purity TiNi alloys.