(1. 江西理工大学 材料科学与工程学院，赣州 341000；
2. 江西理工大学 机电工程学院，赣州 341000)
摘 要: 在双重梯度保温工艺下，研究Gd-Y-Nd-Ce四元稀土复合细化剂对半固态A356铝合金初生相产生多重细化效果。结果表明：共晶产物α(Al)的相对量为99%以上，是细化效率最高的有效形核基底，因此在A356铝合金液相线附近保证其较高的存活率对初生相的细化至关重要；另一共晶产物 RExAly不足1%，其在不同裸露晶面上存在不同的错配度(形核效率)。由于梯度保温对多元共晶产物存活率的调控，使得其在种类、尺寸、数量、错配度等方面展现出多样化。A356-RE铝合金在650 ℃浇注，并按照645 ℃/30 s，635 ℃/40 s，625 ℃/50 s，615 ℃/ 60 s进行梯度保温，水淬后，在优化方案下(0.5%Gd+0.4%Y+0.2%Nd+0.2%Ce，质量分数)，获得的初生相平均等积圆直径为85.118 μm，形状因子为0.786，细化效果最好。
关键字: 四元稀土；双重梯度保温；A356铝合金；半固态；初生相
（1. School of Materials Science and Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, China;
2. School of Mechanical and Electrical Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, China）
Abstract:The multiple refining effect of Gd-Y-Nd-Ce four rare earth composite refiner on the primary phase of semi-solid A356 alloy was studied under dual gradient isothermal holding technique. The results indicate that the eutectic product α(Al) of relative amount is more than 99%, which is the effective nucleation site. Thus ensuring its high survival rate in the near liquidus of A356 alloy was very important for the refinement of primary phase. The other eutectic product RExAly is less than 1%, which has different degree of mismatching (nucleation efficiency) in different exposed grain surfaces. Due to the regulation of multiple eutectic products’ survival efficiency by gradient thermal insulation, which makes them show the diversity in variety, size, quantity, mismatch degree and so on. In this test, A356-RE alloy is poured at 650 ℃, then gradient isothermal holding is carried according to 645 ℃/30 s, 635 ℃/40 s, 625 ℃/50 s, 615 ℃/60 s. After water quenching, under the optimal composition (0.5%Gd+0.4%Y+0.2%Nd+0.2%Ce, mass fraction), the primary phase of A356 alloy with equal-area circle diameter of 85.118μm and shape factor 0.786 is obtained, in which the refining effect is the best.
Key words: four rare earth; dual gradient isothermal holding; A356 alloy; semisolid; primary phase
