Simulational Research On The Portevin-le Chatelier Effect Of 5086 Aluminum-Magnesium Alloy Based On EKMC Model

Portevin-Le Chatelier(PLC)effect will occur during machining or service process of Al-Mg alloy,which will roughen the surface of alloy and lead to rapid reduction of its plasticity and toughness,even cause premature failure and affect service life of materials and structures.Numerical simulation is one of the important ways to study PLC effect of Al-Mg alloy,and it is an importent work to establish the constitutive model which can correctly characterize dynamic response of Al-Mg alloys in plastic stage.Focusing on plastic instability problem of 5086 Al-Mg alloy,the selection and improvement of material constitutive model,as well as characteristics of PLC effect aspects have been studied.The main works obtained are as follows:(1)EKMC constitutive model and application.Firstly,according to PLC effect mechanism of 5086 Al-Mg alloy,the EKMC constitutive model and its corresponding constitutive form are selecteded.Then,on the basis of determined model parameters and solve process,stress-strain curves of 5086 Al-Mg alloy specimens are simulated,and the limitations of EKMC constitutive model are analyzed by means of comparing simulations and experiences.(2)Improved and verified EKMC constitutive model.Firstly,according to the limitation of EKMC constitutive model,the improved method and form of EKMC constitutive model are proposed.Then,the improved model parameters and negative strain rate sensitivity are studied.Lastly,stress-strain curves of 5086 Al-Mg alloy specimense are simulated and the validities of the improved model are verified by simulational and experimental results.(3)Numerical simulations of PLC effect.Based on the modified EKMC constitutive model,numerical simulations of 5086 Al-Mg alloy PLC effect under three different loading strain rates are carried out;Then,the propagation laws and microscopic mechanisms of different types of PLC belts through stress sawtooth and temperature,as well as strain are studied.Finally,the influences of initial conditions on PLC effect preliminarily are discussed.