液锻压力对亚共晶Al-Si合金吊架的组织与性能影响

Effect of liquid forging pressure on microstructure and properties of hypoeutectic Al-Si alloy hanger

研究了液态模锻工艺下,亚共晶Al-Si合金吊架在不同液锻压力下的成形质量、力学性能及不同位置处的微观组织。结果表明,随着压力的增加,铸件的成形质量逐渐提高,液锻压力为128 MPa时,抗拉强度为250.7 MPa,断后伸长率为9.7%,力学性能最好,较0 MPa下的抗拉强化及断后伸长率分别增加了14.5%和547%,之后再增加压力,对吊架的力学性能无明显强化效果。此外,随着压力的增加,晶粒得到细化,Si相逐渐球化,且高压力下团聚现象明显,二次枝晶臂间距(SDAS)先减小后基本保持不变,在154 MPa时取得最小值16.3μm,SDAS仅为0 MPa时的54.2%,比50 MPa液锻压力下SDAS减少24.5%,共晶团尺寸则是先减小再增大,共晶团尺寸为308μm时对基体产生割裂作用,从而影响力学性能。

The forming quality,mechanical properties,and microstructure at different positions of hypoeutectic Al-Si alloy hangers under different liquid forging pressures,with the liquid forging process,were studied.The results show that with the increase of pressure,the forming quality of castings is gradually improved.When the liquid forging pressure is 128MPa,the tensile strength is 250.7MPa,the elongation after fracture is 9.7%,and the mechanical properties are the best.Compared with 0MPa,the tensile strengthening and elongation after fracture of metal mold casting are increased by14.5%and 547%respectively.After that,increasing the pressure has no obvious strengthening effect on the mechanical properties of the hanger.In addition,with the increase of pressure,the grain is refined,the Si phase is gradually spheroidized,and the agglomeration phenomenon is obvious under high pressure.The distance between the secondary dendrite arms(SDAS)decreases at first and then remains almost unchanged,reaching the minimum value of 16.3μm at 154MPa.And the distance between SDAS is only 54.2%of that at 0MPa,which is 24.5%lower than that at 50MPa liquid forging pressure.The eutectic cluster size decreases first and then increases.When the eutectic cell size is 308μm,it will split the matrix,thus affecting the mechanical properties.