Growth mechanisms of multiscale, mound-like surface structures on titanium by femtosecond laser processing

Authors

Edwin Peng, University of Nebraska-LincolnFollow
Ryan Bell, University of Nebraska at KearneyFollow
Craig A. Zuhlke, University of Nebraska-LincolnFollow
Meiyu Wang, University of Nebraska-Lincoln
Dennis R. Alexander, University of Nebraska-LincolnFollow
George Gogos, University of Nebraska-LincolnFollow
Jeffrey E. Shield, University of Nebraska-LincolnFollow

Date of this Version

2017

Citation

JOURNAL OF APPLIED PHYSICS 122, 133108 (2017)

Comments

Copyright Peng et al.

https://doi.org/10.1063/1.4990709

Abstract

Femtosecond laser surface processing (FLSP) can be used to functionalize many surfaces, imparting specialized properties such as increased broadband optical absorption or superhydrophobicity/-hydrophilicity. In this study, the subsurface microstructure of a series of mound-like FLSP structures formed on commercially pure titanium using five combinations of laser fluence and cumulative pulse counts was studied. Using a dual beam Scanning Electron Microscope with a Focused Ion Beam, the subsurface microstructure for each FLSP structure type was revealed by cross-sectioning. The microstructure of the mounds formed using the lowest fluence value consists of the original Ti grains. This is evidence that preferential laser ablation is the primary formation mechanism. However, the underlying microstructure of mounds produced using higher fluence values was composed of a distinct smaller-grained a-Ti region adjacent to the original larger Ti grains remaining deeper beneath the surface. This layer was attributed to resolidification of molten Ti from the hydrodynamic Marangoni effect driven fluid flow of molten Ti, which is the result of the femtosecond pulse interaction with the material.