PSI - Issue 50

N.B. Pugacheva et al. / Procedia Structural Integrity 50 (2023) 251–256

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N.B. Pugacheva et al./ Structural Integrity Procedia 00 (2022) 000 – 000

composite is characterized by some plasticity margin, i.e. the values of h max and C IT are only slightly different from those for the Cu+TiC areas. The TiB 2 particles have a greater strengthening effect than the TiC particles do.

Fig 3. An SEM image of the Cu-Ti-C-B composite with areas of analysis.

Fig 4. Load curves of the constituents of the composite (the digits correspond to the areas marked in Fig. 1).

Table 1. The chemical composition of the composite in the spectra marked in Fig. 3, wt.% Spectrum No. in Fig. 2 Ti C B

Cu

1 2 3

45.5 40.4

13.3 3.5 22.5

19.2 35.8 77.5

balance balance

0

0

The B 4 C particles have a maximum hardness (3332 ± 5.9) HV 0.1, maximum elasticity indices ( Е *, W e , H IT ), and minimum plasticity indices ( h max , φ , C IT ). Obviously, the presence of areas with dissimilar micromechanical properties provides the redistribution of stresses under external loading. The more plastic constituent Cu+TiC (area 1 in Figs. 3 and 4) damps the arising microstresses and prevent the appearance and development of microcracks. It was reported earlier by Smirnov et al. (2014) that the load curves for the structural constituents of alloys allow strain hardening curves to be plotted. In view of the data previously obtained by Smirnov et al. (2016) and Veretennikova et al. (2018), the strain hardening curves for the studied composite are expected to differ. The strain hardening curve for the Cu+TiC constituent must be found in the region of large strains and lower stresses. For the B 4 C particles, it will be shifted into the region of the highest stresses and smaller strains. The stress-strain diagram for the Cu+TiB 2 +TiC constituent must lie in between. Thus, the constituents of the composite must behave differently under external mechanical loading. The B 4 C particles have the highest strength, but they are not able to deform plastically. The constituents with a copper-based solid solution can plastically deform without cracking. It was reported by Smirnov et al. (2016) that the chaotically distributed particles with a maximum hardness cause plastic strain redistribution and localization under external mechanical loading. As a rule, the maximum microstrain values of the plastic constituent are localized near particles with maximum hardness. Table 2. The micromechanical properties of the Cu-Ti-C-B composite

Area No. in Fig. 1

HV 0.1 (±5.9) 517.7 1006.8 3332.0

W t , nJ (±7.3)

W е , nJ (±3.3)

C IT , % 5.0 4.8 0.8

H IT , GPа (±6.2)

E *, GPа (±31)

h max , μm (±0.3)

H IT / E * 0.0217 0.036 0.091

φ , % 81.3 70.5

1 2 3

5.1

253.0 292.3 386.8

94.2 76.2 48.5

17.6 22.5 31.0

2.9 2.1 1.3

10.7 35.3

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