PSI - Issue 43

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Tibor Varmus et al. / Procedia Structural Integrity 43 (2023) 184–189 Tibor Varmus / Structural Integrity Procedia 00 (2022) 000 – 000

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20 µ m

Fig. 2. (a) 3D microstructure of Al2024-RAM2 (red arrow shows build direction), OM; (b) detail of microstructure, OM; (c) details of fine grains, STEM, (d) distribution of titanium, STEM, (e) distribution of lanthanum, STEM, (f) distribution of boron, STEM.

3.2. Surface roughness and hardness The influence of build orientation on surface quality is significant. Surface measurement using a profilometer determined different surface roughness dependi ng on specimen orientation (see Fig. 1a for definition): Rz = 34.1 ± 7 µm characterizes the C specimen and Rz = 34.8 ± 3 µm the B specimen. The lowest roughness of Rz = 5.7 ± 3 µm was found in specimens with build orientation A-. The surface quality of as-built specimens was also investigated on longitudinal metallographic sections. Magnified as-built surface profiles for various orientations are shown next: it was observed that specimen B, Fig. 3b and C, Fig. 3c, have significantly more fragmented surfaces compared to specimens A-, Fig. 3a. Rockwell's hardness was tested on flat as-built surfaces above the notch and the average value of five measurements for all orientations are listed in the Table. 3. The highest value of hardness showed the specimen Type A- orientation.

Table 3. Results of HRB hardness measurements. Orientation Type A-

Type B 72 HRB

Type C 71 HRB

Average value

77 HRB