Recent advances in Ti-6Al-4V additively manufactured by selective laser melting for biomedical implants: Prospect development

Surface modification methods have been applied to metals and alloys to change the surface integrity, obtain superior mechanical properties, and improve service life irrespective of the field of application. In this review paper, current state-of-the-art of peening techniques are demonstrated. More specifically, classical and advanced shot peening (SP), ultrasonic impact peening (UIP), and laser shock peening (LSP) have been discussed. The effect of these techniques on mechanical properties, such as hardness, wear resistance, fatigue life, surface roughness, and corrosion resistance of various metals and alloys, are discussed. This study also reports the comparisons, advantages, challenges, and potential applications of these processes.

Peening Techniques for Surface Modification: Processes, Properties, and Applications.

A cross-scale study on the effect induced by laser shock peening (LSP) and physical vapor deposition (PVD) coating on the wear and corrosion resistance of FeCoCrNiAl high entropy alloys (HEA) has been made in this work. The nano scale FeCoCrNiAl HEA coating on substrate 304 steel and microscale FeCoCrNiAl HEA has been acquired through PVD nanocoating and LSP, respectively. The micro hardness, friction and corrosion properties have been investigated to evaluate the reliability of the material in application. The results of microhardness and wear test indicate that both approaches have increased the surface hardness of HEA through grain refinement. And the results for corrosion test reveal a competing effect between grain refinement and compressive stress. As the enhancement brought by PVD nano coating is not comparable to the cast sample, due to the side effect brought by grain refinement which will reduce the corrosion resistance. Surprisingly, specimens treated with LSP have better performance in corrosion resistance, as the compressive residual stress induced by LSP enhanced the adhesion between the substrate and modified layer, forming dense passive films to inhibit corrosion ions in the environment and successfully neutralized the side effect brought by grain refinement. Therefore, the modified layer induced by LSP on the surface contributes to the improvement of both wear resistance and corrosion resistance. • Effect of LSP and PVD on wear and corrosion resistance of HEA have been studied. • The wear and corrosion resistance of FeCoCrNiAl 0.1 are enhanced. • The grain refinement has a positive effect on the wear properties. • The compressive stress has a positive effect on the corrosion properties. 

A study on the wear and corrosion resistance of high-entropy alloy treated with laser shock peening and PVD coating

A Critical Comparative Review of Cavitation Peening and Other Surface Peening Methods

In this study, high speed impacting tests are systematically conducted on a split Hopkinson pressure bar device to investigate the strain rate and temperature dependence of dynamic compressive properties of Ti-6Al-4 V (TC4) fabricated by selective laser melting (SLM), the ranges of strain rate and temperature are 2000–6000/s and 25–650 ℃, respectively. The results reveal that the yield strength and ultimate compressive strength of the SLM-TC4 alloy increase with the increasing strain rate and the decreasing temperature, showing obvious strain rate and temperature sensitivities. The high speed impacting load intensifies the texture of the SLM-TC4 alloy significantly. Adiabatic shear band (ASB) is more likely to evolve at higher temperatures and strain rates, submicron equiaxed grains formed in the ASB and the surrounding area are mainly ascribed to the combination of dynamic recrystallization, deformation-induced twinning and transverse α-lath splitting. Within the ASB, grains with {0001} pole orientation are rotated by approximately 45° with respect to the shear direction, indicating that the recrystallized grains are able to reorient themselves to accommodate to the shear deformation. The findings in this work provide a theoretical basis to understand the deformation behavior and mechanism of SLM-TC4 alloy under impacting loads, thus is helpful to widen the application of SLM technique and products. 

Dynamic compressive properties and underlying failure mechanisms of selective laser melted Ti-6Al-4V alloy under high temperature and strain rate conditions

Effects of laser shock peening on the hot corrosion behaviour of the selective laser melted Ti6Al4V titanium alloy

Improvement mechanism in stress corrosion resistance of the X70 pipeline steel in hydrogen sulfide solution by massive laser shock peening treatment

The role of annealing heat treatment in high-temperature oxidation resistance of laser powder bed fused Ti6Al4V alloy subjected to massive laser shock peening treatment

ZrSi2/SiO2-Nb2O5/NbSi2 multi-layer coating formed on niobium alloy by HAPC combined with LPDS: microstructure evolution and high temperature oxidation behavior

Understanding the response of the Ti6Al4V alloy undergoing different coverage layers of laser shock peening (LSP) and the strain rate dependence of tensile properties is indispensable for its wide applications. Herein, the Ti6Al4V alloy specimens subjected to different coverage layers of LSP were employed in the uniaxial tensile testing with the strain rate of 0.001 s −1 , 0.005 s −1 , 0.01 s −1 , and 0.02 s −1 . The effects of the coverage layer on the tensile properties and its sensitivity to the strain rate were determined. The relationship between the microstructural morphologies, tensile behaviors , and strengthening mechanism were revealed. Moreover, the corresponding fracture behaviors of the tested specimens were summarized. It evidently shows that, the tensile properties and fracture behaviors of the Ti6Al4V alloy subjected to LSP treatment strongly depend on the strain rate. The ultimate tensile strength and the total elongation exhibit reverse trends with increasing strain rates and coverage layers, also, the typical ductile fracture pattern gradually evolves into the mixed ductility/cleavage fracture simultaneously. Upon the increasing plastic deformation process of LSP, the dislocation density, as well as the grain size are two intrinsic factors for controlling the strain hardening behavior and strain rate sensitivity, and the deformation twin provides another alternative factor. • The effects of the coverage layer on the tensile properties and its sensitivity to the strain rate were determined; • The relationship between the microstructural morphologies, tensile behaviors, and strengthening mechanism were revealed; • The fracture behaviors of the tested specimens at varied strain rates were summarized. 

Zhao Wang

Papers

Effects of laser shock peening on the hot corrosion behaviour of the selective laser melted Ti6Al4V titanium alloy

Improvement mechanism in stress corrosion resistance of the X70 pipeline steel in hydrogen sulfide solution by massive laser shock peening treatment

The role of annealing heat treatment in high-temperature oxidation resistance of laser powder bed fused Ti6Al4V alloy subjected to massive laser shock peening treatment

ZrSi2/SiO2-Nb2O5/NbSi2 multi-layer coating formed on niobium alloy by HAPC combined with LPDS: microstructure evolution and high temperature oxidation behavior

Strain rate dependence of tensile properties and strengthening mechanism of Ti6Al4V alloy undergoing different coverage layers of laser shock peening