OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 4 2023 Fig. 8. Load-penetration curves of instrumental indentation using the AIS3000 HD Indentation with multiple intermittent unloading results in a set of parameters in a wide indentation range, i.e., at different depth of penetration with gradually increasing penetration force. Using these parameters, the reduced elastic modulus is calculated in the whole range of elastoplastic deformation in the indentation zone. The elastic modulus and microhardness, obtained in XZ and XY planes, are shown in fig. 9. As can be seen in fig. 9, а, b, absolute hardness values at different points with the structure shown in fig. 7, а, differ insignificantly, while in-plane hardness values matching structures shown in fig. 7, b, are slightly lower. Similar findings are presented in many works. As for absolute values of the elastic modulus, it differs from each other at different points and planes. As in the case with rolled alloys, the elastic modulus is different in the scanning plane and growth plane (fig. 9, b, c). And its absolute values are considerably lower than those obtained by ultrasonic testing. Micro-indentation of elastic modulus and hardness Load-depth curves in fig. 10 are obtained for four alloys. Great difference in the residual penetration depth indicates different resistance to deformation or hardness of alloys. One can see that after unloading, the residual depth for the VT1-0 alloy is higher than for other alloys. It means that this alloy is softer, while for other alloys, the tangent slope is close to the unloading curve. Table 3 presents the elastic modulus and hardness for Ti alloys measured by various indentation techniques in different planes. In this table, terms longitudinal and vertical mean that the indentation load is applied in XZ and XY rolling planes, respectively. The obtained hardness values correspond to the values inherent in the alloys under study and show a difference depending on the measurement plane, both for rolled material VT1-0 and printed VT6cv. Values of the elastic modulus demonstrate its dependence on the structure and phase composition of Ti alloys. According to Lutfullin et al. [24], in Ti alloys consisting of a hexagonal α-phase and body centered cubic
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