【摘要】 制作了含钼量分别为2.8%、3.3%、4.0%、5.5%和7.5%(质量分数)的IN718合金铸锭。采用金相显微镜、扫描电镜、能谱分析和电子探针研究了钼对IN718合金铸态组织和均匀化处理过程中Laves相溶解及其中元素扩散的影响。研究发现,随着钼含量的增加,合金枝晶干中铌的浓度逐渐降低。由此表明,钼促进铌的凝固偏析。钼明显降低铌、铁和镍在Laves相中的溶解度,因而显著促进Laves相析出,并使Laves相能吸收更多的剩余液体,减小Laves相周围偏析区的面积。高钼IN718合金Laves相中铌、铁和镍含量的降低有助于其连续长大成较大的颗粒状,相反,低钼IN718合金中Laves相则倾向于以Laves+γ共晶方式析出。钼能稍微提高Laves相的熔点,明显延长Laves相的溶解时间,明显延长铌元素在枝晶干和枝晶间扩散的时间,由此表明钼能阻碍铌元素扩散。更多还原

【Abstract】 Cast IN718 alloy ingots containing 2. 8%,3. 3%,4. 0%,5. 5%, and 7.5% Mo by mass were fabricated. The effect of molybdenum contents on the as-cast microstructure, dissolution of Laves phase and diffusion of the elements in IN718 alloy during homogenizing was investigated by OM, SEM, EDS and EPMA.From the results it was seen that with the increase in molybdenum content the concentration of niobium in dendritic trunk lowered because of molybdenum aggravating its segregation formed during solidification of the alloy. In addition, molybdenum rendered dissolubility of niobium, iron and nickel in the Laves phase much less, thus appreciably promoting precipitation of the Laves phase, and allowing it to absorb the more retained liquid, as well as lessening area of segregation zone around the Laves phase. The decrease in contents of niobium, iron and nickel in the Laves phase in the higher-molybdenum IN718 alloy will be beneficial to its continuous growth into larger particles. Conversely, the Laves phase in the lower-molybdenum IN718 alloy will be easy to precipitate in the form of eutectic crystal Laves +γ. Molybdenum may render melting point of the Laves phase slightly higher, and times required for the Laves phase to dissolve and for niobium element to diffuse in dendric trunk and among dendrites noticeably longer, which indicates that it is likely to impede diffusion of niobium.更多还原