Effects of severe plastic deformation on pre-osteoblast cell behavior and proliferation on AISI 304 and Ti-6Al-4V metallic substrates

Abstract

In this study, titanium alloy (Ti-6Al-4V) and austenitic stainless steel (AISI 304) biomedical alloys were subjected to surface severe plastic deformation (SSPD) via severe shot peening (SSP) with the conditions of A28-30 Almen intensity. SSP is widely accepted as much more effective than the conventional surface modification techniques since it forms a nano-grain layer with large number of dislocations and grain boundaries. The SSP treatment in this study was led to a very thin rough layer in Ti-6Al-4V titanium alloy compared to that of AISI 304. The thicker layer of AISI 304 was created by twin-twin intersections and a martensite structure transformations. SSP treatment was resulted in a severe plastically deformed material surface and led to an increase in full width half maximum (FWHM) that expresses grain size reduction below nanometer regime. Also, SSP treatment increased the surface roughness of materials by forming pits and bumps and led to deterioration on surface topography. Besides physical and microstructural innovations, SSP treatment was improved the surface mechanical properties of the metals. On the other hand, it was noted that the effects of the alteration of surface topography and structural innovations (nano-grain crystal-deformation induced layer) were led to improved cellular behavior and increased cell proliferation regardless of material type.