Effects Of Doped Graphene Nanosheets On The Microstructure And Properties Of TC4 Titanium Matrix Composites Formed By Selective Laser Melting

TC4 is the most typical titanium alloy developed by combining α-Ti and β-Ti.It has good comprehensive properties such as low density,high strength,good toughness,and good biocompatibility.However,due to its wear resistance,insufficient strength,etc.The shortcomings limit its wider application.Therefore,in order to solve this problem,an effective method is to prepare high-performance titanium-based composites by reinforcing the titanium alloy matrix to expand its application in various fields.Therefore,in this paper,aerosolized TC4 titanium alloy powder and high-quality graphene nanosheets are selected as the research objects,and the mixed powder of the composite material is printed and formed by selective laser melting.Through microscopic characterization analysis,electrochemical test,hardness test,tensile property test,sliding friction and wear test,and electrochemical pre-charged hydrogen slow strain rate stretching,etc.,the effects of different contents of graphene nanosheets on the microstructure,basic mechanical properties,Sliding friction properties,effects of hydrogen embrittlement resistance.The corresponding impact mechanism is discussed,and the main results obtained are as follows:(1)First,use certain printing parameters(laser power is 340 W,scanning speed is 1250mm/s,scanning layer thickness is 0.06 mm,scanning spacing is 0.12 mm,and the scanning method of layer-by-layer rotation is 67°)to doped graphite.Titanium-based composites with graphene nanosheets(contents of 0.1 wt%,0.2 wt%,0.3 wt%,0.5 wt%)were prepared.The results show that with the increase of graphene content,the strengthening effect has different strengthening,and the grains get After refinement,Ti C particles are distributed around theα-slats,and the phase composition is α-phase with close-packed hexagonal structure andβ-phase with body-centered structure and Ti C generated in situ.The corrosion resistance of the composites in 3.5 wt% Na Cl solution was enhanced.Among them,the content of 0.2 wt%is the best in terms of comprehensive mechanics.At this content,no macroscopic cracks are found in the printed parts,and the hardness value reaches 435.86 HV,which is 23.7% higher than that of pure TC4.The yield strength reaches 1106 MPa,and the tensile strength reaches1189 MPa,an increase of 24%,the elongation after fracture is 10.94%,and the fracture mode is ductile-brittle mixed fracture.(2)With the increase of graphene nanosheet content,the wear volume and roughness decrease,the wear volume decreases by up to 40.8%,and the friction coefficient generally shows a downward trend.The wear mechanism is a combination of various mechanisms,but the fatigue wear is the main factor without the addition of graphene nanosheets,and the abrasive wear is the main factor after the addition of graphene nanosheets.The composition of the wear debris changed from Ti,Al oxides to Ti,Al,C oxides,and the oxygen content was significantly reduced.(3)The presence of hydrogen atoms at the end will cause damage to the strength and plasticity of the titanium-based composites formed by selective laser melting to form graphene nanosheets with different contents.And with the increase of the content of graphene nanosheets,the hydrogen embrittlement sensitivity of the composites increases,and the initiation and propagation of cracks change from transgranular fracture to intergranular fracture.The hydrogen embrittlement mechanism changed from hydride formation cracking to hydrogen induced separation mechanism.In summary,this paper studies the microstructure,mechanical properties,corrosion properties,wear resistance,and hydrogen embrittlement behavior of titanium-based composites by doping graphene nanosheets with different contents.performance.Under the printing parameters of this paper,the graphene nanosheet content of 0.2 wt% has excellent comprehensive mechanical properties,corrosion resistance,and wear resistance,but the sensitivity to hydrogen embrittlement is slightly improved.It provides theoretical basis and technical support for the engineering application of SLM-shaped graphene nanosheets and titanium matrix composites.