Research On The Segregation Behavior Of Liquid Forging Workpiece Of Aluminium Alloy

The workpiece were produced by the method including direct liquid forging and indirect liquid forging to analyze the regional effects of element segregation in order to study the mechanism of element segregation for liquid forging parts;helix sample were produced to study the flow effect of element segregation;the effect of rare-earth element on the element segregation were studied.The orthogonal experiment was adopted to study the effects of process parameters of liquid die forging such as pouring temperature,squeeze pressure,squeeze speed and cooling rate on the segregation of Si,Mg,Cu,Fe,and research the interaction effects of process parameters on the segregation.The following conclusions were obtained:In the hot spot zone of indirect liquid forging,the pouring temperature is the most significant factor for Si and Mg segregation;the cooling rate is the most significant factor for Cu and Fe segregation;the interaction effect between process parameters on the element segregation is smaller.With increasing the pouring temperature,the mass fraction of elements increases,the degree of segregation decreases;with increasing the squeeze pressure,the mass fraction of elements decreases,the degree of segregation increases;with increasing the squeeze rate,the mass fraction of elements increases,the degree of segregation decreases;with increasing the cooling rate,the mass fraction of elements decreases,the degree of segregation decreases.Chilled zone was divided into a upper chilled zone and a lower chilled zone.In the upper chilled zone,the squeeze pressure is the most significant factor for the Si segregation;the pouring temperature is the most significant factor for Mg segregation,the squeeze speed is the most significant factor for Cu segregation;The interaction effect of squeeze pressure and cooling rate is the most significant factor for Fe segregation.In the lower chilled zone,the squeeze pressure is the most significant factor for Si segregation;the interaction of squeeze speed and cooling rate is the most significant factor for Mg segregation;the pouring temperature is the most significant factor for Cu ang Fe segregation.The main factors affecting the segregation of different solute elements are different.The reason is caused by the cooling condition,the element content and the alloy flowing.In the hot spot zone of direct liquid forging,the cooling rate is the significant factor for Si,Mg,and Cu segregation.The interaction effect of the squeeze pressure and the cooling rate is the most significant factor for Fe segregation.With increasing the squeeze speed,the mass fraction of element increases;with increasing the cooling rate,the mass fraction of elements decreases.For the Si and Cu,with increasing the squeeze pressure,the mass fraction of elements decreases;the degree of segregation increases,while the Mg and Cu elements are opposite.The change of microstructure and element segregation along the flow length under directe liquid forging was studied.The positive segregation and the negative segregation appear in the unblocked sample at the pouring temperature 710? for Si and Mg;the type of segregation is positive in the begin and the end of the sample;the type of segregation is negative in the middle of sample.The type of segregation is negative in the blocked sample.The distribution trends of element in the blocked sample is similar as in the unblocked sample.The mass fraction of element is high in the begin the blocked sample;with increasing the length of flowing,the mass fraction of elements decreases.The type of segregation is negative in the whole length in the unblocked sample at the pouring temperature 670? for Si and Mg;with increasing the length of flowing,the mass fraction of element decreases.In the blocked sample,with increasing the length of flowing,first the mass fraction of element increases and then decreases.The degree of superheat has a great influence on the element segregation in the flowing length.In the high degree of superheat,the element segregation have more waves along the flowing length.In the low degree of superheat,the element segregation have less waves along the flowing length.In the unblocked sample,there is no close relationship between the distribution of the element segregation and the flowing length.The effect of the rare-earth Er on the element segregation was studied.The results showe that:Adding Er in Al-Mg-Si alloy can change the equilibrium partition coefficient and the type of segregation of Si and Mg,and change the type and degree of segregation in the last solidification zone.In the hot spot zone,with increasing the content of adding Er,the segregation type of Mg and Si will change to positive segregation from negative,but adding Er have little effect on Cu and Fe segregation.In the hot spot zone,with increasing the content of adding Er,the negative segregation of Si,Cu and Mg gradually increases,but the mass fraction of Fe first decreases and then increases.In the chilling zone,with the increasing the content of adding Er,the negative segregation increases.