Study On The Friction And Wear Properties Of Ti-based Bulk Metallic Glass Matrix Composites

Bulk metallic glass（BMG）,known as a new type of metal material,shows some excellent properties,such as high strength,large elastic limit,superior corrosion resistance and wear resistance because of its unique atomic structure.However,BMG can form localized shear bands and the shear bands expand rapidly upon loading at room temperature,leading to brittle fracture of material and severe restriction of the of BMG application in engineering application.In order to overcome the brittleness of the BMG at room temperature,researchers introduce the second phase of ductility into BMG by means of external addition or endogenous method,thus preventing the extension of the main shear band and promoting the formation of multiple shear bands.In recent years,researchers adjust the composition of the material to in-situ metallic glass matrix composites（MGMCs）,which obtains extensive attention.Bulk metallic glass composites Ti₄₈Zr₂₀Nb₁₂Cu₅Be₁₅ and Ti₄₈Zr₂₀V₁₂Cu₅Be₁₅were prepared using non-consumable vacuum arc furnace water-cooled copper casting method.The morphology and microstructure of bulk metallic glass composites were analyzed by X-ray diffraction（XRD）and scanning electron-microscopy（SEM）.The hardness of the composites were determined by a Vickers hardness tester（HVS-1000）.The friction and wear tests were performed by using a high speed reciprocating wear test apparatus（MFT-R4000）under five different normal loads.The friction and wear properties of MGMCs in dry condition,deionized water and 3.5%NaCl solution were studied,and the wear mechanism was investigated by scanning electron microscopy.The main research contents and conclusions of this paper are as follows.（1）Ti₄₈Zr₂₀Nb₁₂Cu₅Be₁₅ and Ti₄₈Zr₂₀V₁₂Cu₅Be₁₅ are both composed of dendritic and amorphous matrix.And the dendritic phase is BCC structure.The volume fraction of dendrites in Ti₄₈Zr₂₀Nb₁₂Cu₅Be₁₅ and Ti₄₈Zr₂₀V₁₂Cu₅Be₁₅ is 40%and 54.2%respectively,and the hardness of Ti₄₈Zr₂₀V₁₂Cu₅Be₁₅ is higher than that of Ti₄₈Zr₂₀Nb₁₂Cu₅Be₁₅.（2）The average friction coefficient of Ti₄₈Zr₂₀Nb₁₂Cu₅Be₁₅ is minimal in dry condition.In three different conditions,the wear rate decreases with the increase of normal load.In dry condition,the main wear mechanism of Ti₄₈Zr₂₀Nb₁₂Cu₅Be₁₅ is delamination wear,abrasive wear and adhesive wear.In deionized water,the main wear mechanism is abrasive wear and slight adhesive wear.And the main wear mechanism in 3.5%NaCl solution is delamination wear and abrasive wear.On the basis of XPS analysis,TiO₂,Nb₂O₅,NbO and ZrO₂ are generated in 3.5%NaCl solution during the wear test of Ti₄₈Zr₂₀Nb₁₂Cu₅Be_15.（3）The average friction coefficient of Ti₄₈Zr₂₀V₁₂Cu₅Be₁₅ obtains the maximum value in deionized water.In three different conditions,the wear rate of Ti₄₈Zr₂₀V₁₂Cu₅Be₁₅ increases with the increase of normal load,and reaches the maximum when the load is 15 N.In dry condition,the main wear mechanism of Ti₄₈Zr₂₀V₁₂Cu₅Be₁₅ is abrasive wear and adhesive wear.In deionized water,the main wear mechanism is abrasive,and the main wear mechanism in 3.5%NaCl solution is abrasive and adhesive.By XPS analysis,Ti O₂,ZrO₂ and V₂O₃ are generated in 3.5%NaCl solution during the wear test of Ti₄₈Zr₂₀V₁₂Cu₅Be_15.（4）The wear resistance of Ti₄₈Zr₂₀V₁₂Cu₅Be₁₅ is significantly better than that of Ti₄₈Zr₂₀Nb₁₂Cu₅Be₁₅.At the same time,the corrosion resistance of these composites is similar.Therefore,Ti₄₈Zr₂₀V₁₂Cu₅Be₁₅ is more suitable for wear-resisting material in seawater environment.