Additively manufactured ultrastrong Al-containing austenitic stainless steels via engineering cellular structure with multi-nanoprecipitates

Abstract

High-performance austenitic stainless steel with ultrahigh strength is in strong demand across various industries. However, traditional austenitic stainless steels generally exhibit lower strength, particularly at elevated temperatures. In this contribution, an austenitic stainless steel with ultrahigh strength from ambient temperature to elevated temperature was successfully fabricated via laser additive manufacturing. This achievement is realized by engineering incoherent and coherent multi-nanoprecipitates via cellular structure in austenite, including the co-precipitation of incoherent precipitates of Laves phase, B2 phase and Cr-rich α′ phase at the cellular walls and coherent L12 phase within the cellular structure. The cellular dislocation networks in austenite introduce high density incoherent Laves phase within grains by providing massive nucleation sites, followed by the successive formation of B2 phase and Cr-rich α′ phase around the Laves phase. The high density incoherent precipitates within austenite grains not only substantially strengthen the matrix at ambient temperature, but also contribute to the superior strength at elevated temperature significantly through interacting with dislocations and nano SFs. In addition, the co-precipitation structure substantially improves thermal stability of Laves phase. This work provides a methodology for engineering multi-nanoprecipitates via cellular structure to fabricate austenitic stainless steel with superior performance.