| As one of the most widely used titanium alloys,Ti-6Al-4V(TC4)has perfect mechanical properties,corrosion resistance and processing properties and it's usually used in aviation engines,the pipelines and hulls of submarine.these application fields all have higher requirements for material damping performance in order to weaken vibration and use up energy.However,the current TC4 alloy has poor damping performance,which goes against its application of related fields.At present,there is little research that has been done on the improvement of damping properties of TC4 alloy.In this paper,the internal friction characteristics of TC4 alloy will be improved by the combination of anodic oxidation and heat treatment,and the damping mechanism,mechanical properties and corrosion resistance of TC4 alloy will be studied in order to explore a treatment process which can improve the damping properties of TC4,which also has excellent mechanical and corrosion resistance.In this paper,first of all,the influence of anodic oxidation process on TC4 damping performance is studied,and secondly,the influence of heat treatment process on TC4 damping performance is studied.In the last,the influence of composite treatment process(heat treatment + anodic oxidation)on TC4 damping performance is studied.At the same time,the effects of different processes on the mechanical properties and corrosion resistance of TC4 were also studied in this paper.The following results were obtained:(1)The optimum process of TC4 damping performance was obtained by adjusting the process parameters of anodic oxidation:E=30V;t=300S;T=25?;L=30mm.the internal consumption is 0.0183.The experimental results are 5.3 times of the original TC4 internal friction value.Through the heat treatment process parameters debugging,the optimal process for damping the TC4 is obtained:850? Solid solution and water quenching,the internal consumption is 0.0129,which is 3.2 times higher than the original TC4 value.The optimal process for damping the TC4 is obtained by the compound process(heat treatment +anodization)parameter debugging.The optimal process parameters are as follows: E=30V,t=300S,T=25?,L=30mm and 850?solution treatment + water quenching.Its internal consumption is 0.0290,which is 8.2 times higher than the original TC4 value.(2)The main reasons for the anodizing treatment to improve the internal friction of TC4 are as follows: the thermal expansion coefficient of the oxide film and the TC4 metal matrix is greatly different,which leads to stress concentration at the interface,which exceeds the TC4 yield limit,resulting in micro plastic deformation,which in turn induces dislocation generation.Under the action of external force,these G-L dislocations will reciprocate and consume energy,which increases the internal friction of TC4 sample.The mechanism of heat treatment to improve the internal friction of TC4 is mainly due to the soft phase after solid solution water quenching in phase ?? +.Micro plastic deformation occurs under external force and viscoelastic behavior occurs at the interface,which in turn consumes energy to improve TC4 damping performance.The mechanism of the composite treatment process(heat treatment + anodization)to improve the damping properties of TC4 is the superposition of heat treatment and anodizing treatment: G-L dislocation damping mechanism and soft phase micro plastic deformation and viscoelastic behavior at the interface of oxide-metal matrix.(3)The damping properties of TC4 samples obtained by anodizing and heat treatment all show obvious frequency response characteristics,which is closely related to its damping mechanism;temperature changes in the environment will increase the internal friction value and cause damping peak effect.The damping peak generated by anodizing TC4 is mainly related to the heat activation effect,while the damping peak generated by heat treatment TC4 may be related to stress release and tissue change.(4)After anodizing or compounding treatment,the corrosion resistance of TC4 samples has been significantly improved,which is mainly attributed to the protective effect of oxide film.This improvement is closely related to the change of oxidation voltage.The higher oxidation voltage will increase the thickness of oxide film the density,thereby enhancing its corrosion resistance.(5)The yielding strength and micro-hardness of TC4 samples decrease when quenched in phase zone.The micro-hardness and yield strength of TC4 samples are 292.60 HV and 768.19 MPa respectively after quenched at 850?for 30 minutes,while those of untreated TC4 samples are 337.08 HV and 925 MPa,which are mainly due to the existence of softer phases. |
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