| Titanium and titanium alloy has been applied in different industrial areas because of its exceptional corrosion resistance,abrasion resistance,higher specific strength and other excellent performance.As the processing deformation temperature range is wide,and the forming load force is large,titanium alloy is prone to grain coarsening,local overheating and other issues.In order to identify the corresponding structure and forming performance of titanium alloy under different deformation conditions,improve the production efficiency and product quality.It is necessary to analyze the intrinsic workability of the titanium alloy.In this paper,the constitutive relationship and processing maps of Ti-6Al-4V-0.1Ru titanium alloy are set as objectives.The relationship between the flow stress and deformation temperature,strain rate and strain is discussed.The constitutive equation across-phase transformation and optimal combination of process parameters were obtained by observing the microstructural evolution under different deformation conditions.Which provides a strong reference for the actual processing of Ti-6Al-4V-0.1Ru titanium alloy.A series of isothermal compression tests in a wide temperature range of 1023-1323 K and strain rate range of 0.01-10 s-1 with a fixed height reduction of 60% were conducted on a Gleeble-3500 thermo-mechanical simulator.The true stress-strain curves were obtained,and the variation of flow stress with deformation temperature and strain rate was analyzed.Based on the experimental data,the orthogonal experiment was designed to distinguish the effects of different deformation parameters on the stress.The constitutive relation of Ti-6Al-4V-0.1Ru titanium alloy were established by using two constitutive models of Arrhenius and BP-ANN,the prediction results were compared with each other.Then the stress data outside of the experimental conditions were expanded according to the established BP-ANN constitutive model,and the reliability of the extended data is verified by finite element simulation.The strain of 0.1,0.3,0.5,0.7 are selected to make the thermal processing map under each strain condition,and the microstructural evolution of the unstable and safe area were analyzed to determine the best combination of process parameters.Finally,select the strain 0.6,to make the processing map of experimental data and the extended data of BP-ANN constitutive model,verified the reliability of the extended data again.The main contents of this paper are as follows:(1)The compression test of Ti-6Al-4V-0.1Ru titanium alloy was carried out to obtain the stress and strain data.The orthogonal test was used to analyze the influence order of each deformation parameter on the stress.(2)Using the Arrhenius constitutive equation,the constitutive relationship of Ti-6Al-4V-0.1Ru titanium alloy was described by the multiple linear regression and polynomial fitting,and the flow stress under different deformation conditions was predicted.(3)Based on the BP-ANN artificial neural network constitutive model,the modified trainbr algorithm is used to establish the constitutive equation of Ti-6Al-4V-0.1Ru titanium alloy.Comparing the results with the results of Arrhenius constitutive equation,it is proved that BP-ANN has higher precision and stronger prediction ability.Then the experimental data were expanded according to the established BP-ANN constitutive model,the reliability of the extended data was verified by finite element simulation,and a new empirical formula was used to describe the variation of stress before the peak stress.(4)Based on the machining chart theory of dynamic material model(DMM),the thermal processing graphs under different strain conditions were plotted against the experimental data,BP-ANN prediction data and extended data,and the microstructures of the unstable and safe areas were described. |
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