Formation of Fine Holes and Protrusions on Ti-6Al-4V Alloy by Argon-Ion Sputter-Etching

Fabrication of fi ne surface textures is one of the most e ff ective technologies to provide new functions for materials. In this research, argon – ion sputter – etching was applied to an α + β type Ti – 6Al – 4V alloy placed on a SUS304 steel disk at a radio frequency power of 200W, 250W and 300W for 0.9ks to 21.6ks. For the 1013K annealed specimens, fi ne holes smaller than 500nm diameters were densely formed on the surfaces when the sputter power was 250W and sputter time was 0.9ks. However, when the sputter time increased to more than 1.8ks, the holes disappeared and the groups of grain – shaped protrusions were formed in fl at areas. For the 1323K solution – treated specimens, the fi ne holes were also formed at the sputter power of 250W and at a sputter time shorter than 1.8ks. The holes connected to ridge – shaped protrusions with increasing sputter time and fi nally changed to independent and uniformly distributed protrusions. Energy dispersive X – ray analyses revealed an increase in the V and Fe contents on the sputtered surface. This corresponds that the Fe particles arrived from the SUS304 disk dissolved into the alloy and strongly combined with V atoms, which resulted in the selective sputtering of Al and Ti. It is considered that the argon ion radiation has induced the decomposition of surface region to fi ne areas with di ff erent V and Fe contents, and the fi ne holes are formed by preferential sputtering of the lower V and Fe contents areas. ［ doi:10.2320 / jinstmet.J2022011 ］