| Titanium alloy is extensively applied in the fields of energy-chemical industry,marine engineering,aerospace,motor industry and so on because of its excellent performance.TC4 titanium alloy is diffusely used in core components in these fields due to its corrosion resistance,light weight and obdurability.Non isothermal forging is a common processing method of titanium alloy.However,the forged titanium alloy often forms rough and non-uniform microstructure,which has a great influence on the service performance of components.Hence,heat treatment is needed for strengthening.For titanium alloy,solution aging treatment is one of the important means to improve its mechanical properties and strengthen its service properties.Although solution aging improves the strength of titanium alloy forgings,it also brings large residual stress,which will extremely affect the fatigue life,dimensional stability and material strength of forgings.Therefore,quantifying and predicting the residual stress introduced in the solid solution aging process and adjusting it reasonably can further meet the needs of high reliability and long life of titanium alloy forgings.Taking TC4 titanium alloy non-isothermal forgings as the research object,the mapping relationship between process parameters and residual stress of forgings during solution aging was revealed by combining experimental research,numerical simulation and theoretical analysis.The main research contents are as follows1.According to the engineering practice and combined with the properties of TC4 titanium alloy,the key solution aging process parameters were selected,and the reasonable solution aging experiment,residual stress and mechanical performance test were formulated.Based on the numerical simulation of non-isothermal forging,the finite element model of solution aging of TC4 titanium alloy forgings was established and modified with the experimental results,which lays a foundation for the subsequent analysis of the influence of process parameters on residual stress.2.Based on the revised finite element model,the internal residual stress distribution of TC4 titanium alloy forgings was analyzed.The changes of temperature field and stress field,which are the key factors for forming residual stress during solution aging of forgings,were studied.The effects of solution temperature,solution time,aging temperature and aging time on the distribution of residual stress in longitudinal and transverse directions of forgings were investigated respectively.3.Using the modified simulation data as sample,the primary and secondary relationship of the influence of solution aging process parameters on the residual stress of forging was analyzed by orthogonal experiment method,and the optimal process parameter group of residual stress was determined.Combined with regression analysis and BP neural network,the prediction models of residual stress of forgings after solution aging were established respectively.Finally,the two models were compared and analyzed,and the one with higher accuracy was used as the prediction model of residual stress of the forging.The results of this paper clarify the influence law of solution aging process parameters on residual stress of TC4 titanium alloy non-isothermal forgings,which has important engineering guiding significance for reducing the residual stress of TC4 titanium alloy forgings after solution aging and optimizing process parameters. |
