Abstract
In the present work, textured stoichiometric MnCoSi alloys were fabricated by slow-cooling thermal treatment. Microstructure and crystallographic characterization revealed that the textured MnCoSi alloy consists of three different oriented orthorhombic TiNiSi-type martensite variants with their aOrth-axis lying in the cross-section of the rod-like MnCoSi alloy. A giant reversible linear negative thermal expansion (NTE) as much as 9350 ppm was achieved along the aOrth-axis of the textured MnCoSi alloy at a wide operation temperature span from 50 K to 400 K, owing to the antiferromagnetic arrangement. The linear NTE value slightly decreases from 9350 ppm to 9200 ppm with increasing the external magnetic field up to 2 T, which indicates that the present MnCoSi alloy demonstrates a stable NTE effect under external magnetic field. Moreover, during the martensitic transformation, the linear NTE along the aOrth-axis of the textured MnCoSi alloy could be up to 70,000 ppm at about 1200 K.
NSTL
Elsevier