(1. 江西理工大學 材料科學與工程學院，贛州 341000；
2. 江西理工大學 機電工程學院，贛州 341000)
摘 要: 在雙重梯度保溫工藝下，研究Gd-Y-Nd-Ce四元稀土復(fù)合細化劑對半固態(tài)A356鋁合金初生相產(chǎn)生多重細化效果。結(jié)果表明：共晶產(chǎn)物α(Al)的相對量為99%以上，是細化效率最高的有效形核基底，因此在A356鋁合金液相線附近保證其較高的存活率對初生相的細化至關(guān)重要；另一共晶產(chǎn)物 RExAly不足1%，其在不同裸露晶面上存在不同的錯配度(形核效率)。由于梯度保溫對多元共晶產(chǎn)物存活率的調(diào)控，使得其在種類、尺寸、數(shù)量、錯配度等方面展現(xiàn)出多樣化。A356-RE鋁合金在650 ℃澆注，并按照645 ℃/30 s，635 ℃/40 s，625 ℃/50 s，615 ℃/ 60 s進行梯度保溫，水淬后，在優(yōu)化方案下(0.5%Gd+0.4%Y+0.2%Nd+0.2%Ce，質(zhì)量分數(shù))，獲得的初生相平均等積圓直徑為85.118 μm，形狀因子為0.786，細化效果最好。
關(guān)鍵字: 四元稀土；雙重梯度保溫；A356鋁合金；半固態(tài)；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
