Fundamental Improvement of Creep Resistance of New-Generation Nano-Oxide Strengthened Alloys via Hot Rotary Swaging Consolidation.

Jiří Svoboda,Natália Luptáková,Lenka Kunčická,Petr Dymáček,Adam Weiser

doi:10.3390/ma13225217

Abstract

New-generation oxide dispersion-strengthened (ODS) alloys with a high volume fraction of nano-oxides of 5% are intended to become the leading creep- and oxidation-resistant alloys for applications at 1100–1300 °C. Hot consolidation of mechanically alloyed powders by intensive plastic deformation followed by heat treatment of the alloys are the key aspects for achieving top creep properties, typically ensured by a coarse-grained microstructure strengthened with homogeneously dispersed, very stable yttrium nano-oxides. The rotary swaging method proves to be favourable for hot consolidation of the new-generation ODS alloy presented. Compared to specimens consolidated by hot rolling, consolidation by hot rotary swaging predetermines the formation of coarse grains with a very high aspect ratio during subsequent secondary recrystallization. Such a grain morphology increases the creep strength of the new-generation ODS alloy considerably.

Highlights

The development of advanced materials with excellent high-temperature creep and oxidation resistance is one of the most challenging goals of contemporary material research
Two batches of the Fe-10Al-3Y2 O3 -1Ti new-generation oxide dispersion-strengthened (ODS) alloys are prepared by hot consolidation of mechanically alloyed powder using (i) rolling and (ii) rotary swaging
Secondary recrystallization of the hot rotary swaging consolidated specimens featuring ultra-fine-grained microstructure leads to rather coarse grains significantly elongated in the direction of swaging axis

Summary

Introduction

The development of advanced materials with excellent high-temperature creep and oxidation resistance is one of the most challenging goals of contemporary material research. Ni-based superalloy single crystals [1] applicable up to 1100 ◦ C, oxide dispersion-strengthened (ODS) ferritic alloys [2]. Ni-based superalloy single crystals are typically strengthened by about 70% volume fraction of cuboidal γ-precipitates separated by thin channels of disordered γ matrix [4,5]. Al in the superalloys ensures their excellent oxidation resistance. The ODS alloys are strengthened by nano-dispersion of very stable Y-based oxides, typically of 5–20 nm in size and 0.5% volume fraction [6,7]. The ferritic matrix of the ODS alloys allows sufficient alloying by Al (up to 10 wt.%) ensuring their excellent oxidation resistance [8]

Methods

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Discussion

Conclusion