Porosity severely deteriorates the mechanical properties of aluminum alloys. Large-sized and aggregated porosity often occurs in the center of Direct-Chill (DC) cast ingot. The variation of the temperature field in the sump affects the formation of porosity. In the present work, high shear technology was introduced into the DC casting process and the rotation speed and position of the high shear device were precisely controlled based on the measured temperature fields of conventional DC casting to realize the control of the temperature field and study its effects on the microstructure and mechanical properties of DC cast ingot. The results showed that when the temperature of the melt near the shear site (T_S) was close to the temperature of the melt near the center of ingot and at starting position of the slow cooling zone of conventional DC casting (T_G), forced convection can affect the cooling zone which is below the graphite ring in the sump, resulting in uniform microstructure of the ingot. If T_S was above the liquidus and close to T_G (temperature field II), the microstructure shows rod grains with fine secondary dendrite arms, refined porosity and second phase particles. For the lower T_S which is below the liquidus and close to T_G, (temperature field III), the mixed microstructure of spherical grains and small equiaxed was formed. And the increase of size and content of porosity can decrease of mechanical properties of the ingot. The concomitant relationship between floating/spherical grains and porosity was also discovered and discussed.

孔隙率严重恶化了铝合金的机械性能。直冷（DC）铸锭的中心经常出现大尺寸和聚集的气孔。贮槽内温度场的变化影响孔隙的形成。本工作将高剪切技术引入直流铸造工艺中，根据常规直流铸造的实测温度场，精确控制高剪切装置的转速和位置，实现温度场的控制，并对其进行研究。对直流铸锭组织和力学性能的影响。结果表明，当剪切点附近的熔体温度（T _S) 接近铸锭中心附近的熔体温度，在常规直流铸造的缓冷区 (T _G ) 的起始位置，强制对流会影响油底壳中石墨环下方的冷却区，导致在铸锭的均匀微观结构中。如果 T _S高于液相线并接近 T _G（温度场 II），则显微组织显示棒状晶粒，具有细小的二次枝晶臂、细化的孔隙和第二相颗粒。对于低于液相线并接近 T _{G的下 T S}, (温度场 III), 形成了球状晶粒和小等轴晶的混合显微组织。并且孔隙率的尺寸和含量的增加会降低铸锭的力学性能。还发现并讨论了浮动/球形晶粒与孔隙度之间的伴随关系。