Impact of annealing on the martensitic transformation and magnetocaloric properties in all-3d-metal Mn50Ni32Co8Ti10 alloy ribbons

Abstract

The effects of annealing at different temperatures (1053, 1103, 1153 K) on the martensitic transformation (MT) and magnetocaloric effect have been investigated in all-3d-metal Mn50Ni32Co8Ti10 alloy ribbons. In melt-spun ribbons, a coexistence of predominant 5-layer modulated martensite (5 M, monoclinic, space group P2/m) and a small amount of B2-type austenite with a cubic structure is revealed at room temperature (RT), demonstrating that the forward MT temperature (TtFC ) lies just above the RT. After annealing, the coexistence of three different phases, the non-modulated L10 martensite (NM, tetragonal, space group P4/mmm), 5 M martensite, and B2 austenite, and the enhanced intensity of both B2 (400) and L10 (220) characteristic peaks exhibited in X-ray diffraction patterns are suggestive of the fact that TtFC is reducing. The (TtFC )-reduction induced by heat treatment is also confirmed by thermomagnetic measurements. TODC:TtZFCinthissentenceshouldbealsodeletedThe magnetic entropy change maximum also decreases after annealing because the MT slows down. However, it is worth noting that after annealing the effective refrigeration capacity increases more than twice of the melt-spun sample. The origin of (TtFC )-reduction induced by annealing is discussed.