Study On Apparent Viscosity Of High Silicon Aluminum Alloy Semi-solid Slurry

High silica aluminum alloy has a low coefficient of thermal expansion,good wear resistance,heat resistance and other characteristics,to replace the car engine cast iron,cast steel piston,cylinder liner ideal material.The conventional primary structure of the alloy in the form of coarse plate or needle-like form,seriously affected the mechanical properties of the alloy,limiting its industrial applications.In order to improve this phenomenon,the semi-solid slurry preparation technology was used to treat the alloy melt in the early stage,and the semi-solid slurry of the alloy was obtained.And then for high-quality alloy semi-solid slurry extrusion casting,forming pipe parts,the study found that the primary phase along the wall from the outside to the inside and outside the gradient was increasing trend distribution.At the same time,the researchers found that the gradient distribution was similar to that of the centrifugal casting process,The gradient structure obtained by semi-solid extrusion casting is caused by the rheological properties unique to the semi-solid slurry filling process,which leads to the different degree of response in the solid-liquid two-phase filling process.The apparent viscosity is a very important rheological parameter to reveal the mechanism of hydrodynamics and dynamics in the process of semi-solid metal formation.Therefore,this paper studies the apparent viscosity of high silicon aluminum alloy melt.In this paper,high silicon aluminum alloy semi-solid slurry was prepared by rotating rod-induced nucleation method.The high temperature rotary viscometer was designed and fabricated for the apparent viscosity measurement of semi-solid slurry.The effects of the shear rate on the apparent viscosity of the semi-solid slurry were measured and analyzed.The influence of the shear rate on the apparent viscosity of the semi-solid slurry was investigated.The results show that the nucleation of the primary silicon and the iron-rich phase in the Al-25Si-2Fe alloy has obvious refinement effect.With the increase of the rotation speed of the rod,the refinement effect and uniformity of the primary phase in the alloy slurry showed a tendency to weaken after the first strengthening.When the pouring temperature is 780 ? the rotation speed is 600 r/min,the primary phase with the size of 40?50?m can be obtained,the distribution is more uniform.In this paper,the apparent viscosities of Al-25Si,Al-25Si-2Fe,Al-25Si-2Fe-2Mn three kinds of high silicon aluminum alloys were studied.The results show that In the case of natural cooling,with the melt temperature decreases,the apparent viscosity increases,The apparent viscosity increase of Al-25Si-2Fe-2Mn alloy is the largest,and the increase of apparent viscosity of Al-25Si alloy is the smallest.Compared with the same kind of alloy melt,the apparent viscosity of the melt is the slowest in the furnace cooling condition,the fastest growth rate in the case of air cooling.At the same time,the apparent viscosities of the three kinds of semi-solid slurry at 100? to 500 r/min were studied.The results show that the apparent viscosity of the semi-solid slurry decreases with the increase of the shear rate,and the shear thinning phenomenon occurs.The apparent viscosity of Al-25Si alloy semi-solid slurry is reduced from 0.439 Pa·s to 0.277 Pa·s,and the apparent viscosity of Al-25Si-2Fe alloy semi-solid slurry is reduced from 0.508 Pa·s to 0.305 Pa·s,The apparent viscosity of the Al-25Si-2Fe-2Mn alloy semi-solid slurry is reduced from 0.608 Pa s to 0.317 Pa·s.Under the same shear rate,the apparent viscosity of Al-25Si-2Fe-2Mn alloy semi-solid slurry is the highest.