Precipitation behavior of coherent nano-ordered particles in Fe-Mn-Al-Ni shape memory alloys with different Ni contents

In Fe-Mn-Al-based shape memory alloys, the essential strategy for obtaining good superelasticity is precipitating coherent B2 nano-particles by adding Ni element. In the present paper, we investigated the effect of Ni contents on the precipitation behavior of nano-ordered particles in Fe-Mn-Al-Ni alloys subjected to solution treatment followed by water quenching and air cooling, respectively. D0(3) nano-particles were precipitated in water-quenched and air-cooled specimens with the Ni content of 2.1 at.%. However, coherent B2 nano-particles were precipitated in the water-quenched and air-cooled specimens with the Ni contents of 4.0-10.8 at.%. In addition, their average diameters increased linearly with increasing Ni contents, and were 3.4-14.5 nm for the water-quenched specimens and 9.5-32.3 nm for the air-cooled specimens. The precipitation of B2 nano-particles cannot be suppressed even by water quenching owing to the formation of a miscibility gap after adding Ni element in Fe-Mn-Al-Ni alloys.

Automated summary

This study investigated the effect of Ni content on the precipitation behavior of nano-ordered particles in Fe-Mn-Al-Ni alloys. It was found that D0(3) nano-particles were precipitated with a Ni content of 2.1 at.%, while coherent B2 nano-particles were precipitated with Ni contents of 4.0-10.8 at.%. The average diameter of the B2 nano-particles increased linearly with increasing Ni content.