PSI - Issue 2_A

L.L. Meisner et al. / Procedia Structural Integrity 2 (2016) 1465–1472 L.L. Meisner et al./ Structural Integrity Procedia 00 (2016) 000 – 000

1468

4

EBSD/SE/ SEM and TEM images of inclusions observed in this alloy and corresponding SAED pattern. The inclusions have predominantly elongated shape of a few microns in length (Fig. 5a). The distribution of inclusions, in contrast to the commercial TiNi alloy, was inhomogeneous: elongated inclusion clusters were observed intersecting several grains and fine inclusions located both inside the grains and along their boundaries.

(110)

4000

a

(211)

400 b

400

200

44 46 48 50 52 54 0

(310)

(220)

200

(111)

0

8000

b

400

d

Intensity, arb.u. 400

- Ti 2 Ni

200

44 46 48 50 52 54 0

200

(110) 

20 30 40 50 60 70 80 90 100 110 120 130 140 0

2 Tetta, degree

Figure 1. The X-ray diffractograms from samples of commercial (a) and precision (b) TiNi alloys in the initial states before LEHCEB processing. Co-K  radiation.

b

a

a

1

b

Figure 2. Optical images (a, b) of the microstructure on the surface of as received commercial TiNi alloy before LEHCEB processing;

Figure 3. Bright-field TEM images of inclusions in as received commercial TiNi alloy: ( a ) TiC (TiC x O y ), at the depth h = 3 μ m; SAED patterns of inclusion 1 ( a ).

The results of TEM/SAED/EDS analysis showed that the main type of inclusions is Ti 4 Ni 2 O x oxide based on Ti 2 Ni. This phase, as well as Ti 2 Ni intermetallic, has FCC lattice and close lattice parameter [Mueller at.al.(1963)]. This complicates reliable separation of these phases by XRD method, which showed that the major second phase in this alloy is Ti 2 Ni. Note, that a fraction of TiC x O y and Ti 4 Ni 2 C x O y inclusions inherent to commercial TiNi alloy, is insignificant in the precision alloy.