(1. 華南理工大學(xué) 材料科學(xué)與工程學(xué)院，廣州 510640;
2. 廣州鋼鐵企業(yè)集團(tuán)有限公司 有色金屬研究所，廣州 510340)
摘 要: 采用金相顯微鏡、SEM、EDS和差示掃描量熱法(DSC)等手段研究混合稀土(RE)合金添加量對Ti-B-Sr聯(lián)合細(xì)化變質(zhì)的A356 鋁合金顯微組織結(jié)構(gòu)的影響。結(jié)果表明：當(dāng)稀土添加量為0.1%~0.3%(質(zhì)量分?jǐn)?shù))時(shí)，隨著稀土含量的增加，初晶晶胞尺寸、硅相尺寸、二次枝晶臂間距減小，硅相圓整度提高(長徑比降低)；當(dāng)稀土添加量為0.3%時(shí)，初始α(Al)相的平均枝晶胞尺寸為76 mm，二次枝晶間距為11.3 mm，Si相長徑比為2.13；加入0.1%~0.3%的稀土降低了合金的共晶點(diǎn)溫度和初晶a(Al)的形核溫度，并減小組織熔化過程中共晶反應(yīng)的放熱量。
關(guān)鍵字: A356鋁合金；稀土； 混合稀土；晶粒細(xì)化；變質(zhì)處理； 微觀組織
microstructures of A356 alloy
（1. School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China;
2. Non-ferrous Metal Research Institute，Guangzhou Iron and Steel Enterprises Holding Co. Ltd., Guangzhou 510340, China）
Abstract:The effect of RE addition on the microstructures of A356 alloys refined and modified with Ti-B-Sr was investigated by optical microscopy, scanning electron microscopy, energy dispersive spectrometry and differential scanning calorimetry. With the increase of the RE mass fraction in the range of 0.1%−0.3%, the size of primary α(Al) cell, the size of silicon phase and the secondary dendrite arm spacing decrease, and the aspect ratio of silicon phase increases. When the mass fraction RE added is 0.3%, the average size of primary α(Al) cell, the secondary dendrite arm spacing and the aspect ratio of silicon phase are 76 μm, 11.3 μm and 2.13, respectively. 0.1%−0.3％ RE addition makes eutectic temperature and nucleation temperature of primary α(Al) fall down, and lowers the eutectic reaction releasing heat.
Key words: A356 Al alloy; rare earth; mischmetal; grain refining; modification; microstructure
