Effect Of Heat Treatment Process And Deformation On Structure And Properties Of Al-0.2wt.%Zr Alloy

Zirconium has been widely used in production as a trace additive element that can improve the overall performance of aluminum alloys.Zirconium can be added to industrial pure aluminum instead of expensive bismuth to increase heat resistance and inhibit recrystallization,applied to aluminum alloy wires.Zirconium can play a role mainly related to the precipitation of Al3Zr phase.Related studies have shown that the factors affecting the existence of zirconium in aluminum are mainly the addition amount of zirconium,solidification conditions,heat treatment system and plastic deformation.The first two have some research results,but the latter two have little research.Therefore,this paper aims to systematically study the effect of heat treatment system and cold rolling deformation on the precipitation behavior of Al3Zr phase,and then the influence on the microstructure and properties of the material.This paper is mainly carried out from the following contents:(1)Effect of heat treatment process on microstructure and properties of Al-0.2wt.%Zr ingot:comparative analysis of industrial pure aluminum and Al-0.2wt.%Zr ingot in 200-400℃ insulation process The change of conductivity and hardness in the middle and the scanning results were investigated to investigate the effect of low temperature heat treatment on the precipitation behavior of Al3Zr phase.(2)Effect of heat treatment process on microstructure and properties of Al-0.2wt.%Zr sheet:The deformation of the sheet was 71.4%and 92.8%,and the sheet was subjected to the same heat treatment as the ingot after cold rolling,through metallographic,SEM,conductivity,Hardness and other detection analysis,to study the effect of cold deformation on the precipitation behavior of Al3Zr phase.The results of the as-cast samples show that the conductivity and hardness of Al-0.2wt.%Zr alloy ingots are very small during 200℃ and 300℃ insulation,and when the temperature is kept to 100h,the conductivity changes within 1%IACS,and the hardness varies within 2HV.,respectively,and no Al3Zr phase was observed in the aluminum matrix.In the process of heat preservation at 400℃,it was observed that a small amount of Al3Zr phase with small size and uneven distribution was observed when the temperature was kept for 48 hours.The amount of precipitated phase increased with the increase of holding time,and the electrical conductivity and hardness increased continuously.The research on cold-deformed sheet specimens shows that after cold deformation,the grain morphology gradually changes from irregular polygon to long strip shape,and finally becomes fibrous structure.After cold deformation,the conductivity of the sample decreases slightly and the hardness increases remarkably.The addition of Zr element can significantly increase the recrystallization temperature of the aluminum alloy.The industrial pure aluminum plate is completely recrystallized at 300℃ for 4h,while the Al-0.2wt.%Zr plate recrystallizes at 400℃.After 71.4%cold-rolling treatment,8mm thick Al-0.2wt.%Zr plate can be observed at 300℃ and 400℃ for 8h,and the precipitation of Al3Zr phase can be observed.The number of precipitated phases increases with the holding time.However,when the temperature is 400℃,the size of the precipitated phase is finer and higher density due to the influence of recrystallization.The conductivity is constantly increasing at both temperatures.After the cold rolling treatment of 92.8%,the 2mm thick Al-0.2wt.%Zr plate can be observed for a very small amount of Al3Zr phase after being kept at 300℃ and 400℃for 4hwith the deformation amount and holding time.As the number increases,the number of precipitated phases increases gradually,increasing the amount of cold deformation,and the rate of change in conductivity and hardness is faster.