含Fe过共晶Al-Si合金半固态熔体的表观粘度

Apparent Viscosity of Semi-solid Hypereutectic Al-Si Alloy Melt Containing Iron

对半固态Al-17Si-xFe(x=2,3,4)的流变性能进行了研究。测出了Al-17Si-xFe在液相线以上100℃、50℃和液相线以下10℃和40℃的粘度,及连续冷却过程中的粘度-温度曲线,4种温度下Al-17Si-2Fe合金熔体的粘度分别为0.7451、0.7878、0.9224、1.0829Pa·s。当Fe含量从2%增加到4%时,Al-17Si-xFe的定温粘度增大。但Fe含量较高时,在液相线以下40℃随着保温时间的增加,Fe相的析出和沉降也较严重,会一定程度上减小熔体的表观粘度。随着剪切时间的增加,Al-17Si-xFe合金熔体在液相线以下40℃的表观粘度先减小后增大;在连续冷却的过程中,随着温度的连续降低,熔体的固相率逐渐增大,熔体的表观粘度随之增大,但增加比较缓慢;当温度降低到固相线附近的时候,Al-17Si-xFe熔体表观粘度会急剧增大。另外,在相同剪切速率下,达到相同的固相率时,冷却速度越快,熔体表观粘度就越大。

With a help of a viscometer, the rheological properties of semi-solid Al-17Si-xFe（x----2,3,4, weight percentage,%） prepared were analyzed. The viscosity of Al-17Si-xFe in the constant tempera- tures of 100 ℃,50℃ above the liquidus and 10 ℃,40 ℃ below the liquidus, respectively, was meas- ured, and the viscosity - temperature curve in the continuous cooling process was presented. The results show that the viscosities in the previous temperatures reaches 0. 745 1,0. 787 8,0. 922 4,1. 082 9 Pa · s , respectively, which show with the temperature decreases, the viscosity is increased. With the iron con- tent increasing from 2% to 4%, the viscosity of the alloys is increased too. However, with a higher iron content, the precipitation and sedimentation of the iron phases becomes serious in the temperature of 40 ℃ below the liquidus with increasing in the holding time, which results in the decrease of the apparent viscosity of the melt to some extent. With increasing in the shearing time, the apparent viscosity of the alloys in the temperature of 40 ℃ below the liquidus is decreased firstly and then increased. In the con- tinuous cooling process, with the continuous decrease of the temperature, the solid fraction of the melt is gradually increased, and the apparent viscosity of the melt is increased slowly. When the temperature is reduced to some temperature near the solidus, the apparent viscosity of Al-17Si-xFe alloys is increased rapidly. In addition, at the same shear rate and to achieve the same solid fraction, the apparent viscosity of the melt in increased with the increase of cooling rate.