铸造速度和混合稀土对Al-23%Si合金组织和性能的影响

研究了半连续铸造过程中不同铸造速度及铈镧混合稀土对Al-23%Si合金微观组织和力学性能的影响.结果表明:当铸造速度从100 mm/min提高到250 mm/min时,Al-23%Si合金初晶硅的偏析现象得到有效改善,铸锭从内部到外部初晶硅的分布都较为均匀,初晶硅的平均尺寸从71.4μm下降到40.9μm,同时减轻了共晶硅的偏析.加入0.5%的铈镧混合稀土后,Al-23%Si合金的共晶组织产生了明显变化,稀土元素细化了合金的共晶组织,并使共晶硅相由层片状转变为短杆状.提高铸造速度和添加混合稀土可提高合金硬度和抗拉强度.

Effects of Casting Speed and Mischmetal on Microstructure and Mechanical Properties of Al-23%Si Alloy

The effects of different direct chilling casting speed and mischmetal (i.e.，Ce and La elements) addition on microstructure and mechanical properties of Al-23%Si were investigated. The results showed that when the casting speed increases from 100mm/min to 250mm/min， the segregation of primary Si is restricted effectively， the distribution of primary Si becomes more uniform in different positions of the ingot， the size of primary Si is greatly decreased from 71.4μm to 40.9μm and the segregation of eutectic Si is also reduced. With an addition of 0.5% mischmetal， the size of eutectic Si refines and its morphology changes from flake-like shape to short rod-like one. Both hardness and tensile strength increase with the increase of DC casting speed and the addition of mischmetal.