(1. 上海交通大學(xué) 材料科學(xué)與工程學(xué)院，
上海 200030；
2. 南通工學(xué)院 機(jī)械工程系，南通 226007)
摘 要: 將含有稀土的熔劑JDN-Ⅰ用于覆蓋處理A356合金。實(shí)驗(yàn)結(jié)果表明，該稀土熔劑對(duì)A356合金的二次枝晶臂間距dDAS值有著較大的影響。無(wú)熔劑覆蓋時(shí)，水淬獲得的dDAS值比空冷下降30.8%；有JDN-Ⅰ熔劑覆蓋時(shí)，水淬獲得的dDAS值比空冷下降88.2%；水淬時(shí)，有熔劑覆蓋的dDAS 值比無(wú)熔劑覆蓋低77.7％；空冷時(shí)，有熔劑覆蓋的dDAS 值比無(wú)熔劑覆蓋高23.3％。分析認(rèn)為，存在2個(gè)臨界冷速v1和v2：當(dāng)冷速v<v1時(shí)，dDAS值由液相線斜率決定；當(dāng)v>v2時(shí)，dDAS值由JDN-Ⅰ熔劑中的稀土含量決定；當(dāng)v1＜v＜v2時(shí)，dDAS值由凝固時(shí)間稀土含量和液相線斜率三者共同決定。
關(guān)鍵字: 稀土熔劑；A356合金；二次枝晶臂間距
secondary dendrite arm spacing
of A356 alloy
JIANG Hai-yan1， DING Wen-jiang1
（1. School of Materials Science and Engineering，
Shanghai Jiaotong University， Shanghai 200030， China;
2. Department of Mechanical Engineering，
Nantong Institute of Technology，Nantong 226007，China）
Abstract:A rare earth flux—JDN-Ⅰ was used for A356 alloys by covering on the surface of the melt. The experimental results indicate that the rare earth flux affects the secondary dendritic arm spacing (dDAS) of A356 alloy. The dDAS obtained by water-quenching decreases by 30.8% in comparison with that by air-cooling without the covering of the flux，while the dDAS obtained by water-quenching decreases by 88.2% in comparison with that by air cooling with the covering of JDN-Ⅰ flux. It is suggested that there are two critical cooling rates，v1 and v2. If the cooling rate v<v1，the dDAS is primarily determined by slope of liquidus(/M/) which is determined by the compositions， diffusion coefficient of the alloy. If v>v2，the dDAS is determined by the ［RE］ of JDN-Ⅰ flux and solidification time tf. If v1＜v＜v2，the dDAS is determined by tf ，[RE］ and M together.
Key words: rare earth flux; A356 alloy; secondary dendritic arm spacing
