New Approach to Produce a Nanocrystalline Layer on Surface of a Large Size Pure Titanium Plate

Yuzhu Fu,Jing Gao,Ge Wang,Weiping Tong,Quantong Yao

doi:10.3390/coatings10050430

Abstract

It was demonstrated that the mechanical shot peening (MSP) technique was a viable way to obtain a nanocrystalline layer on a large size pure titanium plate due to the MSP provided for severe plastic deformation (SPD) of surface high velocity balls impacting. The MSP effects of various durations in producing the surface nanocrystalline layer was characterized by optical microscope (OM), X-ray diffraction (XRD), transmission electron microscope (TEM), and Vickers micro-hardness tester. The results showed that the thickness of the SPD layer gradually increased with the MSP processing time increase, but saturated at 230 μm after 30 min. The average grain size was refined to about 18.48 nm in the nanocrystalline layer. There was equiaxed grain morphology with random crystallographic orientation in the topmost surface. By comparing with the nanocrystalline layer, acquired by surface mechanical attrition treatment (SMAT), the microstructure and properties of the nanocrystalline layer acquired by MSP was evidently superior to that of the SMAT, but the production time was cut to about a quarter of the time used for the SMAT method.

Highlights

Titanium and its alloys have attracted abundant interests because of their exceptional performance, such as high specific strength, low density, exceptional corrosion resistance, and biocompatibility, compared with conventional materials [1,2,3,4]
The major contribution of this study was offering a new method for obtaining a nanocrystalline layer on a large size plate
The effect of mechanical shot peening (MSP) and surface mechanical attrition treatment (SMAT) on the microstructure surface roughness, and hardness was investigated. These conclusions can be drawn from the present evolution, surface roughness, and hardness was investigated

Summary

Introduction

Titanium and its alloys have attracted abundant interests because of their exceptional performance, such as high specific strength, low density, exceptional corrosion resistance, and biocompatibility, compared with conventional materials [1,2,3,4]. Some performances and working reliability of titanium and its alloys still need to be enhanced due to the continuous development of technology [5,6]. Lu et al in 1999 [8], a variety of SNC methods, such as ultrasonic shot peening (USSP) [9], high energy shot peening (HESP) [10], equal-channel angular pressing (ECAP) [11], high pressure torsion (HPT) [12], surface mechanical grinding treatments (SMGT) [13], SMAT [14], etc. Of the above-mentioned methods, surface mechanical attrition treatment (SMAT)

Objectives

Results

Conclusion