Study On The Effect Of Thermal Field And Pre-torsion Strain On Mechanical Properties Of Magnesium Alloys

Mechanical Properties of Magnesium AlloysMagnesium alloy is one of the most commonly used and lightest metal structural materials.It has the advantages of low density,high specific strength and specific stiffness,good damping,noise reduction and recyclability.It is widely used in cylinder head cover and variable speed.Aerospace military products such as box casings,clutch pedals,and other aerospace military products such as aircraft wings,aircraft engines,and motor casings.Among them,as an engine and the like,the magnesium alloy usually works in a high temperature environment.The plasticity of magnesium alloy is poor at room temperature.High temperature conditions can greatly improve the plasticity of magnesium alloys.Pre-torsion strain can increase the tensile strength of magnesium alloys.The variation of flow stress and the effect of torsional rate and pre-twist on the mechanical properties of magnesium alloys are studied.The study of mechanical properties under service conditions is of great significance for improving the practical application value of materials engineering.The main research work carried out in this paper is as follows:(1)Based on the research status at home and abroad in related fields,this paper conducts debugging and calibration research on the multi-load multi-physics material micro-mechanical performance in-situ test instrument independently researched and developed by the research group.The calculation of the rack compliance is carried out by the rate method.The tensile calibration test was carried out on 45 steel,7075 aluminum alloy,7050 aluminum alloy and TA2 material,and the error of the elastic modulus caused by the special composite fixture of the test instrument was calibrated,and the elastic modulus and the true elastic modulus of the material were calculated.(2)In this paper,the tensile and torsion tests of AZ80 magnesium alloy were carried out by using the modified calibration instrument to obtain the yield strength,tensile strength,elongation after fracture and the modulus of elasticity after calibration.At the same time,the AZ80 magnesium alloy was subjected to different rates.Tensile test to rule out the effect of different stretching rates on the test results.(3)In this paper,high temperature tensile,torsion test,pre-torsional tensile test and high temperature-pre-torsional tensile test were carried out on AZ80 magnesium alloy material.On the one hand,the function of the test instrument in the tensile-twist composite load and high temperature test was verified.In combination with the normal temperature tensile and torsion tests to study the effects of high temperature and pretorsion strain on the mechanical properties of AZ80 magnesium alloy,three conclusions are obtained: as the temperature increases,the strength of AZ80 magnesium alloy decreases but the shaping performance is very large.The AZ80 magnesium alloy exhibits high hot workability when the torsion rate is 10 and the temperature is 400 °C.When the pre-torsional is 0-60°,the strength of the AZ80 magnesium alloy increases with the increase of the pre-twist angle.As the pre-torsional angle continues to increase,the elastic deformation properties of AZ80 magnesium alloy are greatly reduced,and the plastic deformation changes little.Under the joint action of high temperature and pre-torsion strain,the strength of AZ80 magnesium alloy and the plasticity of the material can be guaranteed.performance.(4)In this paper,the constitutive relation model of typical materials is briefly introduced.It is found that the J-C constitutive model is suitable for thermal coupling analysis and easy to solve.By fitting the stress-strain curve of the AZ80 magnesium alloy at room temperature and quasi-static tensile test,the relevant parameters of the JC constitutive model are obtained.The ABAQUS simulation analysis of the AZ80 magnesium alloy is carried out to supplement the high temperature conditions that cannot be achieved by the test,and the pre-torsional is supplemented.The strain value is further refined to analyze its effect on the mechanical properties of the material.