| Titanium alloy has become one of the key supporting material of modern aerospaceand national defense industry by virtue of its comprehensive mechanical properties, lowdensity, excellent corrosion resistance, outstanding high-heat tensile strength, creepstrength and high-temperature stability. However, mechanics properties, such as the bigcutting force, high cutting temperature and small modulus of elasticity, together with theuneven distribution of initial residual stress make the distortion issue due to millingprocess for monolithic component of titanium alloy complicated, which have a seriousinfluence on producing efficiency and product accuracy of monolithic component oftitanium alloy. Currently, study on distortion due to milling process of monolithiccomponent solely take macrostress into consideration without considering microstress,which is short of dependable theory basis in resolving the distortion issue. This paper isbased on study of the distortion reasons and research status overseas and domestic,takes microstress into consideration in the distortion due to milling process by using thecombination of theory and experiment method, which research systematically theinfluence rules of distortion due to milling process of monolithic component of titaniumalloy by virtue of microstress, and announce the essence mechanism of distortion due tomilling process of monolithic component of titanium alloy based on considering therecombination action of macrostress and microstress.Above all, the formation characteristics and laws of dislocation and stacking faultduring machining deformation of titanium alloy monolithic component are studied byexperiment in this paper. The observation and analysis on SADP, TEM BFI and HREMIare carried out to make clear the main characteristics of dislocation and stacking faultduring machining deformation. Results show that the inner dislocation of TC4has adrastic movement because of the difference on titanium alloy materials, stacking faultsare hardly found in all HREMI, the influence of stacking faults can be ignored in thesubsequent study, and this experiment is the base of further study towards thecalculation of microstress.Then, the related basic theory based on X-ray stress test experiment are studied, based on which all factors causing diffracted ray width effect are analyzedcomprehensively. After ruling out the influence of stacking faults towards diffracted rayby virtue of the TEM experiment results, the crystal block size which is hard toseparated is discussed significantly. The calculation method of microstress elaboratedparticularly, that is deconvolution between the crystal block size and microstress withthe X-ray width effect of microstress, which is the research foundation of influencerules what microstess to distortion due to milling process for monolithic component oftitanium alloy.At last, based on the above research, the experiment of milling and X-ray stresstest are carried out. Microstress produced by milling process is calculated by thecalculation method of microstress, the distortion rules, macrostress rules andmicrostress rules in different distortion stages are obtained. Meanwhile, the essencemechanism of distortion due to milling process of monolithic component of titaniumalloy is studied comprehensively combined with the function of macrostress,conclusions can be draw: macrostress released rapidly and balanced in a short time afterfinishing the milling process and taking off clamping, which makes the rapid distortionhappen, subsequently, microstress which released slowly lead to the subsequent slowdistortion. The recombination action of macrostress and microstress created the birthand transformation of distortion of monolithic component. |
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