Effect of construction orientation on the microstructure and properties of SLM Ti alloy clasps

Abstract

Objective To investigate the physical properties of Ti⁃6Al⁃4V clasps generated by selective laser melt⁃ ing (SLM) with different construction directions and to compare these clasps with cast clasps, which could provide a ba⁃ sis for fabricating SLM clasps with high precision and excellent mechanical properties. Methods Ti⁃6Al⁃4V clasps were fabricated by SLM at 0 degrees (SLM0 group), 45 degrees (SLM45 group) and 90 degrees (SLM90 group) (n = 12). Twelve clasps were cast by the casting method as the control group. Meanwhile, four metal abutments were cast random⁃ ly as the abutments of the four groups. X⁃ray was used to detect cracks in the clasps of each group. The roughness of the clasps was measured by confocal microscopy, the fitness tests between clasps and abutment were processed by stereomi⁃ croscopy, and the microstructure of clasps in each group was observed under a metallographic microscope to evaluate the physical properties. Results There were 0⁃8 visible cracks in the casting group but no obvious defects in the SLM groups. The maximum surface roughness was observed in the cast group (18.102 ± 3.762) μm, while the minimum roughness was observed in the SLM90 group (5.942 ± 1.486) μm (P < 0.05). There was no statistically significant differ⁃ ence in surface roughness between the SLM0 group [(8.711 ± 2.378) μm] and the SLM45 group [(8.513 ± 1.161) μm]. Fitness was worst in the casting group [(68.445 ± 14.876) μm] and best in the SLM90 group [(33.417 ± 5.880) μm] (P < 0.05). There was no statistically significant difference in fitness between the SLM0 group [(52.917 ± 12.102) μm] and the SLM45 group [(50.889 ± 7.011) μm]. In addition, the growth direction of the β grains was roughly parallel to the build direction, and acicular α grains were present between β grains. SLM was composed of fine grains, while the cast group had large grains. Conclusions Specimens generated by SLM had finer grains than cast specimens. In addi⁃ tion, SLM90 clasps had the highest fitness and the lowest surface roughness.

Keywords

• Selective laser melting，
• Ti⁃6Al⁃4V clasps，
• Construction orientation，
• Anisotropy，
• Metallography，