Ageing effects on ordering degree and morphology of 18R-type martensite in shape memory CuZnAl alloys

Structural and Morphological Investigations on Shape Memory CuZnAl Alloys

“…The grain size of lower side of figure was measured as 350 µm. The structures marked by long arrows in the same grain are defined as V-type martensite plates [12,13]. It has been observed that martensite plates continue to there at grains or grain boundary and they cannot pass to another grain.…”

“…The upper side of Fig. 4a shows the V-type self-accommodating growth with four variants contained in a plate group [12][13][14]. As indicated by long arrows, parallel bands on plates in the middle and V-typed some plates of Fig.…”

“…When the reason of this formation is compared with β phase, lower symmetry of martensite structure leads to the formation of many martensite plate variants having a lot of different tendencies in a β phase grain. These kinds of structure are characterised with 6 variant groups consisting of 4 different single-crystal each of which directed differently [12][13][14][15][16][17]. Figure 5b shows the micrograph taken from alloy 2 sample aged for 4 h at 200…”

“…3 number sub-grain is directed by a wider angle considering 1,2,4,5 number sub-grains. Bending angles occurring during the transfer of martensite plates to a sub-grain are harmonious with [10][11][12][13][14][15][16][17][18][19][20] • deviation angles given in literature [14][15][16][17][18]. It has been known that sub-grain is smaller than β-phase grains and they are 50 µm [15].…”

Long-term ageing behaviour of martensite in shape memory Cu–Al–Ni alloys

“…It has been reported that the basal plane of 18R martensites originates from one of the {1 1 0} ␤ planes of the matrix and the inhomogeneous shear occurs on the basal plane in either of two opposite directions during the transformation [10][11][12][13][14][15]. The fundamental structures of the ␤-type martensites are orthorhombic close-packed structures, which consist of an array of close-packed planes as shown in Fig.…”