Stress-induced transition from modulated 14M to non-modulated martensite in Ni–Mn–Ga alloy. (15th May 2015)

• Record Type: Journal Article
• Authors: Ge, Y.; Zárubová, N.; Heczko, O.; Hannula, S-P.
• Is Part Of: Acta materialia. Volume 90(2015)
• Page Start: 151
• Page End: 160
• Publication Date: 2015-05-15
• Subjects: Ni–Mn–Ga -- In situ TEM -- Magnetic shape memory -- Twinning dislocation -- Intermartensitic transition; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2015.02.028
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: Observation of in situ straining of seven-layered (14M) martensite of Ni–Mn–Ga alloy was carried out by a transmission electron microscope (TEM). During straining, the intermartensitic transition from 14M to non-modulated martensite (NM) occurred via motion of partial dislocation with a Burgers vector b = 1/6[1 1 ¯ 0] along the basal plane of 14M. High resolution TEM studies revealed that the moving partial at the end of the fault is actually a pair of partial dislocations leading to a two-layered fault on the basal plane. This fault is twin related to the adjoining five-layered basal plane forming complete seven-layered nanotwinned structure. The results demonstrate that the 14M to NM transition is a detwinning process of these nanotwins, and seems to confirm the nanotwin nature of the long-period stacking-order structure of 14M martensite. The lattice parameters of the average structure are strongly affected by the regularity of the stacking sequence, i.e., by the volume fraction of the two-layer nanotwins and their distribution.