Microstructure of the mechanically alloyed and electrochemically etched Ti-6Al-4V and Ti-15Zr-4Nb nanocrystalline alloys

Formation of the Ti-6Al-4V and the Ti-15Zr-4Nb porous nanocrystalline alloys was described. The alloys were prepared by mechanical alloying (MA) followed by pressing, sintering and subsequent anodic electrochemical etching in 1 M H3PO4 + 2% HF electrolyte at 10 V for 30 min. The microstructure was investigated by XRD, TEM and SEM. We found that the mechanically alloyed powders are composed from nanostructure grains, whose size increases during the high temperature sintering. The final ultrafine grains improve subsequent etching process. The electrolyte penetrates sinters through the grain boundaries, resulting in effective grains removing and pores formation. The porosity of the Ti-15Zr-4Nb alloy is larger than that of the Ti-6Al-4V alloy. The macropore diameter reaches up to 40 μm, while the average micropore size is in the range from 3.5 to 5.46 nm for the Ti-15Zr-4Nb and the Ti-6Al-4V electrochemically etched alloys, respectively. The prepared porous ultrafine alloys could be possible candidate for a hard tissue implant applications, where the pores in the surface improve bonding of the implant with bone.