Experimental Study On Femtosecond Laser Processing Of Medical Bulk Metallic Glass

Compared with commonly used implant materials such as medical stainless steel,titanium and their alloys,medical bulk metallic glass have the excellent properties of bioglass and biometallic materials,including excellent mechanical properties,corrosion resistance and biocompatibility.It has great potential in the field of biomedicine.At present,the commonly used medical materials have the problems of biological inertia and low binding degree,and usually need complex surface treatment to improve their biocompatibility.Amorphous alloys are in metastable structure.the common surface treatment methods will destroy their unique structure and affect their physical and chemical properties.Femtosecond laser processing has very short pulse width,high temporal and spatial resolution,minimal impact on the matrix,and great advantages in material surface treatment.Therefore,it is of great significance to develop a new generation of femtosecond laser processing for medical bulk amorphous alloy.In order to achieve high efficiency and high quality surface treatment of amorphous alloy,based on relevant theories and experimental studies,Zr₆₁Ti₂Cu₂₅Al₁₂ medical bulk amorphous alloy material was selected.The single point ablation,marking and large area structure preparation experiments were carried out by femtosecond laser,the ablation threshold of the material was calculated,and the microstructure,elemental composition and wettability of the processed surface were detected and analyzed.The main research contents are as follows:?1?The ablation thresholds of Zr₆₁Ti₂Cu₂₅Al₁₂ amorphous alloy under different pulses were studied.Based on the laser ablation threshold theory,single point ablation test was carried out by designing different energy and pulse number.The relationship between the ablation hole diameter,morphology size and laser parameters was established by using the optical profilograph,and the ablation threshold value under different pulse number was obtained.?2?The single-point ablation test and groove marking test of femtosecond laser under different parameters were studied.The morphology and element composition of femtosecond laser processing under multi-parameters were analyzed by SEM and EDS.The results show that femtosecond laser machining can oxidize the material surface.With the increase of laser power or pulse number,deep hole ablation zone and micro-nano structure modification zone appear in the amorphous alloy.When grooving is carried out,low speed will lead to more surface deposits.With the continuous increase of laser speed,material removal decreases.Under impact pressure,ablation products can be effectively removed,and the surface quality gradually improves.At the same time,it was found that the accumulation of energy at low speed may"clean"the oxide layer on both sides of the tank.?3?The surface wettability of amorphous alloy after femtosecond laser processing was studied.The surface before and after femtosecond laser processing was measured by a contact angle measuring instrument and compared with another measurement three months later.The results show that Zr₆₁Ti₂Cu₂₅Al₁₂2 amorphous alloy itself has hydrophilic properties,and the contact angles of different structure surfaces prepared by femtosecond laser are significantly reduced,showing excellent hydrophilic properties.At the same time,it is also found that after sitting in the air for three months,the contact angle of the unmachined surface decreases,the contact angle of the machined surface increases,and the hydrophilic characteristics decrease.?4?The surface chemical composition of the raw amorphous alloy and the surface after three months of processing were studied.The element composition and possible compounds on the surface of the two groups were analyzed by XPS.The results show that the passivation layer composed mainly of zirconia is formed in the air.The reason of weak hydrophilicity was also analyzed from the point of view of hydrophobic groups on the surface.The research results of this subject can provide technical support and reference for femtosecond laser precision machining of medical amorphous alloy,preparation of hydrophilic surface and surface treatment of implant.