The Research On The Influence Of Scandium On The Microstructure And Mechanical Properties Of Al-6Zn-2Mg-2.5Cu Alloy

Al-Zn-Mg-Cu alloy is widely used in the modern industry, because of its highstrength, high hardness, high toughness and corrosion resistence. The traditionalplastic mold material-die steel is facing production of difference, long processing timeand high cost problems, so it is very necessary to develop a new plastic mold materialwhich could replace the die steel.The mian research of this paper is the influence ofscandium on the mircostructure and mechanical properties at room temperature ofAl-6Zn-2Mg-2.5Cu alloys, and explore the optimization of composition and heattreatment process. In addition, we hope to provide theoretical support to thedevelopment of new aluminium plastic mold material.In order to research on the influence of the rare earth element-scandium on themircostructure and mechanical properties at room temperature of Al-6Zn-2Mg-2.5Cualloys, we would study this alloy on cast, solution and age.In this paper, we observe, detect and analyze the mircostructure, mechanicalproperties at room temperature, phase composition and distribution of the castAl-6Zn-2Mg-2.5Cu alloys whose content of scandium are0,0.1%,0.2%,0.3%and0.4%, and the change of the mircostructure, mechanical properties at roomtemperature, phase composition and distribution of those alloys with the content ofscandium increasing are compared to find outthe effect of scandium on the themircostructure and mechanical properties at room temperatureof the castAl-6Zn-2Mg-2.5Cu alloys. In addition, we research on the instrinsic relationshipbetween its mechanical properties and the change of its mircostructure, and analyzeits influence mechanism. Experimental results show that scandium have a obviouseffect on grain refinement of the cast Al-6Zn-2Mg-2.5Cu alloys, and make its grainfrom dendrite to equiaxed grain; in addition, increasing the content of scandium affectthe distribution of those eutectic phaseand change the their phase composition.Therare earth element scandium affect the size and type of the grain, composition anddistribution of eutectic phase to influence mechanical properties at room temperatureof the cast Al-6Zn-2Mg-2.5Cu alloys. In this paper, in order to study the effect of scandium on the solution treatmentmircostructure of Al-6Zn-2Mg-2.5Cu alloys, we observe distribution of the insoluableprecipitated phase with different scandium content of alloys, and we detect thechemical composition of them by EDS. Experimental results show that most ofinsoluable precipitated phase gradually reduce, even completely disappear with thecontent of scandium increasing.For studying the influence of scandium on the agetreatment mircostructure and mechanical properties at the room temperature ofAl-6Zn-2Mg-2.5Cu alloys,the paper is not only that observes, detectes and analyzesthe effect of increasing content of scandium on the mircostructure and mechanicalproperties at the room temperature, but also compares mechanical properties at theroom temperature of the alloys which is treated by age treatment with differentheating temperature and holding time, and analyzes the influence of age treatment onthe mircostructure to find out the best heating treatment process. Experimental resultsshow that increasing the content of scandium have a obvious effect on precipitatedphase particles in the grain and microsegregation area which make a greatcontribution to the mechanical properties at the room temperature of age treated alloys.In addition, when the content of scandium in alloy is0.2%, and we take120℃-24hage heating treatment process to treat the alloy, the comprehensive mechanicalproperties at the room temperature of Al-6Zn-2Mg-2.5Cu alloys is the best.