PSI - Issue 40

N.B. Pugacheva et al. / Procedia Structural Integrity 40 (2022) 372–377 N.B. Pugacheva, T.M. Bykova / Structural Integrity Procedia 00 (2022) 000 – 000

376

5

Table 2. Results of indentation of structural components of the composite. The zones indicated in Fig. 2 H IT, GPа (±0.7) HV0.1 (±74) E*, GPа (±13) W t , mJ (±0,03)

W e , mJ (±0,005)

h max , μm (±0,11)

h p , μm (±0,12)

h 1 , μm (±0,11)

I

5.59

528.6

270.1

0.92

0.17

2.89

2.32

2.78

2

7.59

717.7

314.1

0,51

0.17

2.52

1.96

2.42

3

8.64

816.4

314.3

0.80

0.18

2.39

1.76

2.29

4

9.08

858.8

327.8

0.76

0.18

2.34

1.8

2.23

Table 3. Calculated parameters of the micromechanical properties of the composite. The zones indicated in Fig.2 R е , % H IT /E* H IT 3 /E* 2 ,

φ , %

IT , %

C

1 2 3 4

19,72 22,22 26,35 23,07

0,020 0,024 0,027 0,027

0,0024 0,0044 0,0065 0,0069

82 80

3,95 4,13 4,36 4,93

77,5 76,3

Composite strength during transverse bending tests R bm = 620 - 640 MPa. The character of specimen fractures after testing corresponds to ductile fracture. The “γ - Fe + TiC” regions fracture with the formation of shallow pits, at the bottom of which TiC particles are located (Fig. 3a). The TiB 2 particles are large - Pugacheva et al. (2019); therefore, upon destruction, they are sources of the formation of larger and deeper pits (Fig. 3b). The “γ -Fe + Fe 2 B” eutectic regions are destroyed with the formation of a honeycomb relief characteristic of cast alloys (Fig. 3, c). When dendrites in the eutectic are located perpendicular to the fracture surface, plastic deformation of the axes of Fe 2 B dendrites occurs with the formation of hollow tubes (Fig. 3d), which is consistent with the previously obtained data on the deformation of these borides – Pugacheva et al. (2020). The regions "γ -Fe + Fe 2 B" have a positive effect on the structural strength of the composite of the Fe-Ni-Ti-C-B system, since they inhibit the development of cracks, firstly, due to stress relaxation in plastic austenite, and secondly, due to the large work of fracture dendritic framework of Fe 2 B borides. a b