Internal friction behavior of Ni_(50.5)Mni_(25)Ga_(24.5)alloy with cellular microstructure

Ni_(50.5)Mn_(25)Ga_(24.5)alloy with cellular microstructure was fabricated.The effect of the cellular microstructure on the internal friction(IF)behavior associated with martensitic transformation(MT),premartensitic transformation(PMT)and twin boundary motion(TBM)was investigated.Compared with conventional NiMn-Ga alloys,the temperature span of the IF_(MT)peak is significantly expanded,the IF_(PMT)is weakened,and no IF_(TBM)is detected.Both IF_(MT)and IF_(PMT)in the cellular microstructure exhibit unique frequency dispersion feature which has never been observed in conventional Ni-Mn-Ga alloys.The effect of point defects associated with the cellular microstructure is considered to understand the observed results.