Study Of Al-TiO₂-C Refiners On ZL101 Refining Performance

Due to their excellent castability and lower density,ZL101 alloys are the most important and most widely used aluminum alloy in aerospace,automotive,ship and other fields.However,a unmodified alloy structure contains large needle eutectic silicon which greatly aggravate the comprehensive mechanical properties.Refiner is the most simple and effective method to refine and modify ZL101 alloy.At present,the application technology and development of refiner is immature and imperfection,as a consequence,it is necessary to further study in the preparation process and mechanism of refiner.Al-TiO₂-C refiners were synthesized by the in-situ exothermic dispersion method.In the grain refiner performance test,the refiners were added to ZL101 alloys.Effect of pressure,adding amount,sintering temperature,Ti:C and rare earth on refining performance were discussed.The microstructure and phase structure under different conditions was investigated by OM,SEM,EDS analysis as well as XRD,furthermore,the effect of refiners on grain size of ZL101 alloy and eutectic Si nucleation and growth was analyzed by thermal analysis,the results as follow.Al-TiO₂-C refiners are composed of Al₃Ti,Al₂O₃ and TiC,in addition to the three phases,there are a small amount of Ti2 Al20 La phase in rare earth,this phase promotes refining and modifying effect of the Al-TiO₂-C refiners on ZL101 alloy;Al₃Ti,TiC and Al₂O₃ can be used as heterogeneous nucleation to refine ZL101 al oy.When the pressure is 90 kN,the sintering reaction is more complete,the TiC,Al₂O₃ and Al₃Ti phases are massive and the microstructure is distributed uniformly.Compared with the ZL101 alloy without the refiner,the average grain diameter of the ZL101 alloy is reduced from 105.7?m to 66?m,the Al-TiO₂-C refiners have a better refining effect.When the adding amount is 0.3wt.%,the effective nucleation core in the unit melt is saturated,so the best addition amount of the refiner is 0.3wt.%.When the sintering temperature is 1250?,Al₃Ti is round block,and the number of Al₂O₃ and TiC phases is the maximum.The average grain diameter of the ZL101 alloy refined is 73.3 ?m,the Al-TiO₂-C refiners have a better refining effect.When Ti:C is 10:1,the number of Al₃Ti is the most,Al₃Ti is round block,TiC and Al₂O₃ are distribution in grain boundary.The average grain diameter of ZL101 alloy is 71.3?m,the characteristic value ?T1 is 0.4?,?TE is 14.4?,The Al-TiO₂-C refiners possess good refinement effect and ideal modifying effect.When the Pressure is 90 kN,sintering temperature is 1250?,Ti:C is 10:1,the content of La₂O₃ was 0.3wt.%,the grain size reduced to 64.5?m,eutectic silicon became smaller that morphology present rod or granular,the characteristic value ?T1 is 0.3?,?TE is 16.8?,this refiner has the best refining and modifying effect.