Effect of martensitic phase transformation on the ductility of polycrystalline YCu

The tensile deformation behaviour of an extruded, polycrystalline YCu intermetallic compound was investigated from room temperature down to 77 K. A stress-induced martensitic transformation of the cubic B2 to the orthorhombic B27 phase was observed. The increasing amount of B27 phase with decreasing temperature leads to a decrease in ductility. A drastic decrease sets in at about 160 K when thermally induced martensite is formed, characterizing the brittle-to-ductile transition of YCu. Reasons for the relatively high ductility above 160 K are discussed.