OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 4 2023 Today, the widespread instrumental indentation technique allows measuring the elastic modulus in real conditions, which also provides detection of other strength properties such as tensile strength, yield strength, crack resistance [32, 33]. This work presents studies on measuring the elastic modulus and hardness using ultrasonic gauging and macro- and micro-indentation of VT6sv titanium plates. The latter are fabricated by wire-feed EBAM and its properties are compared to those of VT1-0, VT6 and Ti-6Al-4V alloys obtained by conventional techniques. Discussion of measurement results obtained for the elastic modulus and hardness by various techniques assists in further understanding of the obtained values on the structure and phase composition of AM-fabricated Ti alloys. Methodology Materials In our experiments, the Ti alloy was fabricated by wire-feed EBAM using the welding titanium wire VT6sv with a diameter of 1.6 mm. The chemical composition of this wire met the requirements of GOST 27265. It differed from the VT6 alloy in that the content of alloying elements corresponds to the lower limit of alloying values. Also, VT1-0 (Grade 2), VT6 and Ti-6Al-4V titanium rolled sheets were investigated. The chemical composition of VT1-0 and VT6 alloys matched GOST 19807–91, whereas the composition of the Ti-6Al-4V alloy corresponded to the China national standard GB/T 3620.1-2016. This is summarized in Table 1. Ta b l e 1 Chemical composition of titanium alloys Alloys Ti Al V Zr Si Fe O H N C Impurities VT1-0 (Grade 2)* Base – – – 0.10 0.25 0.20 0.010 0.04 0.07 0.10 VT6* Base 5.3–6.8 3.5–5.3 0.30 0.10 0.60 0.20 0.015 0.05 0.10 0.30 Ti-6Al-4V** Base 5.5–6.75 3.5–4.5 – – 0.3 0.20 0.015 0.05 0.08 0.4 VT6sv*** Base 3.5–4.5 2.5–3.5 – 0.10 0.15 0.12 0.003 0.04 0.50 0.30 * GOST 19807–91 ** GB/T 3620.1-2016 *** GOST 27265–87 Alloy specimens were fabricated on a laboratory EBAM system developed in the Institute of Strength Physics and Materials Science SB RAS [34]. The EBAM process was performed in vacuum, at a pressure ranging between 10–3 and 10–2 Pa. The 150×60×2.5 mm3 titanium VT1-0 substrate was positioned on a 160×60×5 mm3 protective layer made of stainless steel. All this was mounted to a triaxial working table via metal clamps. The working table was equipped with liquid cooling, and during printing the temperature was maintained at 13–15 ℃. After the 20th layer, the beam current was reduced from 55 to 40 mA to decrease the heat input. CAD-assisted 3D printing provided the fabrication of 100×60×8 mm3 plate, one plate is demonstrated in Fig. 1, а. The obtained plates were milled and polished for ultrasonic gauging, indentation, and hardness measurement in 89×39×3 mm3 areas indicated in Fig. 1, b. Ultrasonic gauging In order to detect the elastic modulus and hardness by ultrasonic gauging, instrumental indentation and metallography, the electric discharge machining was used for cutting test specimens from different sectors of the plate. Cutting was performed according to the requirements for specimen dimensions in these measuring techniques.
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