稀土Ce对ADC12铝合金铸态微观组织与性能的影响

Effect of Rare Earth Ce on As-Cast Microstructure and Properties of ADC12 Aluminum Alloy

摘要: 采用重力铸造制备了ADC12-xCe (x = 0~1.92)合金铸态试样，利用光学显微镜(OM)、扫描电子显微镜(SEM)和X射线衍射仪(XRD)分析了其微观组织和相组成，测试了其流动性能和室温拉伸力学性能。结果表明，ADC12合金中添加Ce后，铸态组织得到明显细化，初生α-Al从粗大的树枝晶转变为细小的等轴晶和胞状晶，针状的共晶硅转变为细小的颗粒状，同时析出丝状和条状的新相Al₄Ce，大多数第二相趋于以条状和纤维状存在。随着Ce含量的增加，铸态综合性能先提高后降低。ADC12合金流动长度、抗拉强度和伸长率分别为1287 mm、188 MPa和1.5%，流动性能最佳的ADC12-0.66Ce合金流动长度达到1340 mm，拉伸力学性能最佳的ADC12-1.07Ce合金抗拉强度和伸长率分别提高至196 MPa和2.5%。

Abstract: As-cast ADC12-xCe (x = 0 - 1.92) alloy samples were prepared by gravity casting. The microstruc-tures and phase compositions were studied by optical microscope (OM), scanning electron micro-scope (SEM) and X-ray diffraction (XRD). Meanwhile, the flow property and tensile mechanical properties at ambient temperature were tested. The results show that as-cast microstructure is refined significantly when Ce is added into ADC12 alloy. Primary α-Al changes from the coarse dendrites to fine equixed and cellular grains, and eutectic silicon does from acicular to fibrous or granular shapes. Meanwhile, the filamentous and strip new phase Al₄Ce is precipitated. Most of second phases tend to exist in the form of strip and fiber. With increasing the Ce content, as-cast comprehensive properties are first enhanced, and then reduced. The flow length, tensile strength and elongation of ADC12 alloy are 1287 mm, 188 MPa and 1.5%, respectively. The flow length of ADC12-0.66Ce alloy with best flow performance reaches 1340 mm. The tensile strength and elon-gation of ADC12-1.07Ce alloy with best tensile mechanical properties increase up to 196 MPa and 2.5%, respectively.