| Ti6Al4V alloy is used in many fields such as military industry and people's livelihood because of its good comprehensive performance.And solution-aged Ti6Al4 V alloy occupies a large market share.Solid solution and aging treatment improves the strength and hardness of Ti6Al4 V alloy,but it is very limited for improving the inherent poor friction and wear properties of Ti6Al4 V alloy.Surface modification technology can indeed improve the friction and wear resistance of solution-aged Ti6Al4 V alloy,which also increases industrial production cost,process complexity and quality control difficulty.Therefore,it is necessary to determine the wear safety condition in which surface modification is considered to be redundant.In this paper,the friction and wear properties of solution-aged Ti6Al4 V alloy were studied,and the wear behavior and mild-severe wear transition mechanism of solution-aged Ti6Al4 V alloy were analyzed,aiming to determine the wear safety zone and provide reference for engineering application.In this paper,the friction and wear behaviors of Ti6Al4 V alloy treated by solution and aging at 970 °C in dual-phase region and at 1020 °C in single-phase region were comprehensively and systematically described at 20–200 °C and 10–240 N.At each ambient temperature,wear rates and friction coefficients were expressed as functions of the applied load.Combined with the test results of surface composition and surface morphology,the surface wear mechanism was analyzed to determine the mild wear safety zone.Then the mechanism of mild-severe wear transition was explored by analyzing the microstructure and hardness change of worn subsurface.Finally,the influence of two different solution and aging treatment processes on the wear properties of Ti6Al4 V alloy was analyzed by mathematical model.The main research results are as follows :(1)The two kinds of solution-aged Ti6Al4 V alloys were found to have a mild wear stage and a severe wear stage.At a mild wear stage,the wear rate curves increased slowly with the increase of load;at a severe wear stage,the wear rate curves increased rapidly with the increase of load.With the increase of ambient temperature,the mildsevere wear transition load gradually decreased.The mild-severe wear transition load point of 970 ? dual-phase solution-aged Ti6Al4 V alloy decreased from 130 N at 20 °C to 75 N at 200 °C,and the mild-severe wear transition load of 1020 ? single-phase solution-aged Ti6Al4 V alloy decreased from 130 N at 20 °C to 75 N at 200 °C.(2)At a mild wear stage,the main wear mechanisms of worn surface were spall of oxide layer,slight plastic deformation and adhesion.At a severe wear stage,the main wear mechanisms of worn surface were severe plastic deformation and adhesion.Severe surface plastic deformation was the main feature of severe wear.By drawing the wear mechanism diagrams,the load–temperature ranges of two solution-aged Ti6Al4 V alloys were determined for their safe use.Compared with dual-phase solution-aged Ti6Al4 V alloy,the spall of oxide layer of single-phase solution-aged Ti6Al4 V alloy would remain in a larger temperature-load range,which helped to slow down the increase rate of wear rate during a mild wear stage.(3)At a mild wear stage,the friction-affected zone of worn subsurface of solutionaged Ti6Al4 V alloy was mainly plastic deformation zone,and the increase of ? phase caused by thermomechanical effect decreased the hardness of plastic deformation microstructure.At a severe wear stage,the friction-affected zone included plastic deformation zone and microstructure refinement layer.The hardness of the alloy in plastic deformation zone decreased due to the increase of ? phase.In the microstructure refinement layer closest to the worn surface,the dynamic recrystallization(DRX)transformation made worn surfaces soften sharply.DRX was the root cause of severe wear.(4)It was found that the mild-severe wear transition load of Ti6Al4 V alloy decreased linearly with ambient temperature regardless of whether it was treated by solid solution and aging treatment.It indicated that the mild-severe wear transition followed the surface DRX temperature criterion.Through the calculation model of mild-severe wear transition load,it could be deduced that corresponding to mild-severe wear transition,the DRX temperature of the original annealed Ti6Al4 V alloy was558.11 °C,the DRX temperature of 970 ? dual-phase solution-aged Ti6Al4 V alloy was 446.09 °C,and the DRX temperature of 1020 ? single-phase solution-aged Ti6Al4 V alloy was 413.19 °C.The solution and aging treatment reduced the critical DRX temperature of Ti6Al4 V alloy corresponding to mild-severe wear transition. |
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