Modelling On Yield Strength Prediction Of ZL205A Aluminum During Quenching-Aging Process For Aerospace Components

Rocket is an important way for human beings to explore the universe.It has been increasingly evaluated by many countries and has become an important symbol for measuring the comprehensive national strength of a country.Nowadays,as humans accelerate the speed of exploring the universe,the demand for rockets is also increasing,so the requirements of low-cost and high efficiency are put forward for the rockets.ZL205A aluminum-copper alloy is a heat treatable alloy,which has been widely used in the manufacture process of large-scale components of rockets.Its mechanical properties mainly depend on heat treatment conditions,including solid solution,quenching and aging treatment.The Quenching Factor Analysis Method(QFA)has been widely used to describe the effects of continuous quenching on the properties of materials,especially for analysis aluminum alloys and steels.The model is based on Time-Temperature-Property(TTP)curves or Time-Temperature-Transformation(TTT)curves and is calculated by the quenching process based on quenching rate curves.The amount of loss of performance is used to predict the properties of the material,but the material TTT curve is difficult to obtain accurately from the experiment.The TTP curve is widely used to overcome this issue,because the curve is drawn at the same time according to different quenching rates.The material's yield strength value has been got,but the model can only predict the yield strength of the material at different quenching rates for a certain period of time.The precipitation strengthening model(PS Model)focuses on the influence of the evolution process of the physical parameters of the precipitates on the material properties during the aging treatment process.The model can predict the evolution of the material's yield strength throughout the aging process,while the amount of loss of precipitates after quenching is required as input parameter.Based on the above two analytical models,this paper proposes the concept of equivalent iso-thermal temperature(EIQT): At a certain quenching rate,the amount of precipitates in the quenching process is equal to the amount of precipitates in a certain temperature iso-thermal process.This is because the precipitates in the quenching process are mainly stable ? phase,which is consistent with the precipitates in the iso-thermal process.If the amount of precipitates in this part is equal under these two processes,then in the subsequent aging process,the evolution of the ?' phase is also consistent,so the evolution of yield strength would be consistent.The phase diagram of ZL205 A alloy can be used in combination with the PS Model to calculate the yield strength evolution of the alloy under different temperature iso-thermal.When the QFA calculates a certain aging time point yield strength,the calculated yield strength is consistent with the yield strength evolution of a quenching rate calculated by the QFA model at this iso-thermal temperature.In this way,the EIQT model is established to couple the above two models to predict the evolution of yield strength of the alloy during quenching-aging.The influence of Cd atoms on the precipitation process of ZL205 A aluminum alloy was analyzed by first-principles calculation.The calculation results show that the Cd atom can significantly reduce the interfacial energy of the ?' phase and promote the formation of the ?' phase,thus affecting the precipitation process of the alloy.Based on the existing five-stage precipitation model,the boundary of the five-stage precipitation process is divided from the perspective of free energy change,and the validity of the five-stage model is verified by TEM and EDS experiments.Through various tests of yield strength under different quenching rates and different aging time,most of the yield strength evolution of the alloy is consistent with the predicted results of the coupling model.The coupling model was embedded in the UMAT subroutine by ABAQUS simulation software and the evolution of yield strength of the large-scale component during heat treatment was calculated.