Basic Research On Secondary Foaming Of Continuous Casting Of Endogenous Submicron TiB 2 /ZL111 Composite Foam

Aluminum foam possess these properties as light weight,high specific strength,absorption impact energy,damping,sound absorption.It has a wide range application prospects in the construction,aerospace,automobile production and so on.However,the continuous preparation of aluminum foam has not yet been achieved,which limits the large-scale application of aluminum foam.This paper focuses on stability control of low-viscosity aluminum melt foam,in-situ TiB2/ZL111 composite foam was successfully prepared by mixed salt reaction(LSM)and the two steps foaming method.The relevant problems of continuous preparation of TiB2/ZL111 composites were studied,such as the preparation of composite matrix and composite matrix foam,the fluidity of composite melt and the stability of composite foam.The main results are as follows:(1)In-situ TiB2/ZL111 composites prepared by method of mixed salt reaction in ZL111 alloy,most of the TiB2 particle size is less than 0.5μm reaching the submicron level.In-situ TiB2 can refine the grains of the a-A1 and the eutectic Si in ZL111 alloy.With the TiB2 content ’increase,ZL111 grain reduced,the uniformity of microstructures also increased.(2)In-situ TiB2/ZL111 composite foam was successfully prepared by the two steps foaming method.The optimal parameters were as follows:content of TiB22wt%;melting and heat preservation temperature of alloy 615 ℃;content of M g 1%;stirring time 4min;content of foaming agent 0.5%;dispersion time 100s;pressure 60t;foaming temperature 620 ℃;foaming time 10min.(3)The higher the casting temperature,the better the flowability of TiB2/ZL111;the higher the TiB2 content,the worse the flowability of TiB2/ZL111;Compared with ZL111 alloy with 2wt%Ca,the fluidity of 2 wt%TiB2/ZLl 11 is 20.4%higher.In the,the effect of casting temperature(T)on 2wt%in-situ TiB2/ZL111 fluidity(LT)and content of TiB2(X)on in-situ TiB2/ZL111 fluidity(Lx)can be described by exponential damping model。(4)The influence factors of melt stability are viscosity、second phase and surface tension.The TiB2 particles are mainly distributed in the cell walls.TiB2 network,which hinders the flow of the melt,effectively reduce the interfacial tension of gas-liquid and improves the melt stability;Adding 1%of Mg,can effectively reduce the surface tension,improve melt stability.