| Aluminum alloy,as an important engineering material,has been widely used in various industrial fields.With the development of modern industry,the demand for aluminum alloy is increasing,and the demand for mechanical properties of aluminum alloy is increasing.However,the traditional aluminum alloy has the problem of coarse grain size after casting and solidification,and the defects such as composition segregation,crack and shrinkage hole are often caused by coarse grain size.All those defects seriously affect the mechanical properties of aluminum alloy.Therefore,it has become the research focus of aluminum alloy workers to refine the grain and optimize the microstructure of aluminum alloy.In modern industry,adding grain refiner to aluminum melt has become the most simple and effective method to refine aluminum alloy grain and improve the mechanical properties of aluminum alloy.The development of aluminum alloy industry calls for the development of new and efficient refiners.At present,the research on the refinement of aluminum alloys mostly focuses on the theoretical mechanism of grain refinement,refinement process,refiner,type and amount of modifier.Moreover,the mechanical behavior of aluminum detection is too simple.It is common to study the basic mechanical properties under static and quasi-static conditions,and the study on the influence of the addition of refiner on the mechanical behavior of aluminum alloy dynamic load is seldom seen.The macroscopic mechanical properties and behaviors exhibited by the materials are closely related to their internal microstructures,but there is still no in-depth regularity study on the relationship between the two.Based on the above background,the refining agent Al-Ti-Mg-Ce was firstly prepared,and the microstructure of aluminum alloy under the action of new refiner was studied.The synergistic refinement mechanism of Al-Ti and Mg-Ce was analyzed to study the refinement effect.Secondly,the basic mechanical properties of aluminum alloy under static load were tested,and the microscopic mechanism of mechanical properties change was analyzed.The mechanical properties of Al-Si alloy under dynamic load were tested by experiment and finite element simulation.The strain rate effect of Al-Si alloy prepared in this paper was analyzed The main research contents of this paper were as follows:(1)The refiner of Al-5Ti-xCe and Al-5Ti-x(Mg-30%Ce)was prepared to study the refinement effect of Ce and Mg-Ce on Al-5Ti middle alloy.The refining effect was most obvious when the amount of rare earth Ce was 0.6%.Compared with the refining effect of Ce,the refining effect of Mg-Ce on TiAl3 in Al-5Ti was more prominent,this was because Ce in the Mg-30%Ce alloy mainly existed in MgCe10.3.When Mg-30%Ce was added to Al-5Ti melt,MgCe10.3 phase was melted,and rich magnesium was formed at the interface between TiAl3 phase and Al,promoting TiAl3 phase size reduction and improving rare earth refining effect.(2)Al-7Si-(Al-5Ti-xCe)and Al-7Si-(Al-5Ti-x(Mg-30%Ce))alloy was prepared to study the effect of rare earth refining agent Al-5Ti-xCe?Al-5Ti-x(Mg-30%Ce)on microstructure of Al-Si alloy.The refining effect was most obvious when Ce added in finisher was 0.6%.The refining effect of Al-5Ti-x(Mg-30%Ce)was better than that of Al-5Ti-xCe.It was speculated that Mg element stimulates the refining effect of rare earth Ce,which was consistent with the rule of grain size change in the refiner.(3)The basic mechanical properties of aluminum silicon alloy after refining were studied,and it was found that the refiners Al-5Ti-xCe?Al-5Ti-x(Mg-30%Ce)had significant influences on the mechanical properties of aluminum alloy.Besides,it could significantly improve the tensile properties,hardness,impact toughness and yield strength of aluminum alloy under dynamic load.The mechanics performance change trend was consistent with the refiner refining effect.The microscopic mechanism of mechanical properties was analyzed,the result showed not only the grain size decreased but also grain boundary increased and and eutectic silicon structure was improved after adding the refiner Al-5Ti-xCe and Al-5Ti-x(Mg-30%Ce).All of these could provide dislocation resistance,hindering the further development of dislocation,and thus improving the macroscopic mechanical properties.(4)Three kinds of Al-Si alloys were selected to carry out SHPB tests,including Al-7Si-(Al-5Ti)?Al-7Si-(Al-5Ti-0.6Ce)?Al-7Si-(Al-5Ti-2(Mg-30%Ce)).The results showed that the strain rate sensitivity of Al-Si alloy prepared in this paper was significant under high strain rate conditions(above 2.0×103s-1).With the same bullet velocity,the anti-impact properties of Al-7Si-(Al-5Ti-2(Mg-30%Ce))specimens were the best.(5)The SHPB simulation analysis of Al-7Si-(Al-5Ti)and Al-7Si-(Al-5Ti-2(Mg-30%Ce))samples was carried out by finite element method.The numerical simulation was in good agreement with the experimental results.It further verified that the Al-7Si alloy prepared in this paper was a rate-related material The impact resistance of Al-7Si-(Al-5Ti-2(Mg-30%Ce))was superior than that of Al-7Si-(Al-5Ti),which was consistent with the experimental results of microstructure and mechanical properties of Al-Si alloy.In this paper,the microstructure of refiner and aluminum silicon alloy after refining was observed,and the refining effect and mechanism were analyzed.The mechanical properties of aluminum silicon alloy were studied systematically and the microscopic mechanism of mechanical behavior was analyzed.The research results of this paper will provide new reference for the production efficiency,stable and offers cost of refining agent,and provide a theoretical reference and application basis for the further development of high performance aluminum alloy research. |
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