(1. 西北工業(yè)大學(xué) 凝固技術(shù)國(guó)家重點(diǎn)實(shí)驗(yàn)室，西安 710072；
2. 南昌航空大學(xué) 輕合金加工科學(xué)與技術(shù)國(guó)防重點(diǎn)學(xué)科實(shí)驗(yàn)室，南昌 330063)
摘 要: 采用熔融玻璃凈化與循環(huán)過(guò)熱相結(jié)合手段，研究Co70Cu30和Co50Cu50亞穩(wěn)不混溶合金的非平衡凝固組織細(xì)化規(guī)律。結(jié)果表明：隨著過(guò)冷度的增加，不混溶合金的初生枝晶主干不斷細(xì)化，枝晶碎斷現(xiàn)象更加明顯。在未發(fā)生液相分離條件下，Co50Cu50合金由于具有更高的溶質(zhì)含量，溶質(zhì)過(guò)冷度增加，動(dòng)力學(xué)過(guò)冷度降低，枝晶細(xì)化更加明顯而易發(fā)生碎斷。在大過(guò)冷度條件下，合金不混溶效應(yīng)不斷增強(qiáng)，液相分離現(xiàn)象發(fā)生，凝固組織中分別出現(xiàn)富Co和富Cu區(qū)。對(duì)于Co70Cu30(ΔT=237 K)和Co50Cu50(ΔT=188 K)合金，溶質(zhì)含量對(duì)快速凝固過(guò)程中初生枝晶的影響程度減弱，非平衡凝固組織的晶粒尺寸及成分未發(fā)生明顯變化。Co50Cu50合金由于具有更低的臨界分離過(guò)冷度，不混溶階段經(jīng)歷的時(shí)間更長(zhǎng)，液相分離進(jìn)行得更徹底。
關(guān)鍵字: 不混溶合金；非平衡凝固；晶粒細(xì)化；相變動(dòng)力學(xué)
（1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University,
Xi’an 710072, China;
2. National Defence Key Discipline Laboratory of Light Alloy Processing Sc）
Abstract:Adopting molten glass purification combined with cycle superheating method, the effect of solute content on grain refinement regularity of Co70Cu30 and Co50Cu50 immiscible alloys was investigated under non-equilibrium condition. With the increase of initial undercooling, the trunk of primary dendrite decreases, which generates serious dendrite fragmentation. For samples without liquid separation, the solute undercooling of Co50Cu50 alloy increases because of its higher solute content. Consequently, the kinetics undercooling for growth is suppressed, which leads to refined and broken-up dendrite. With the further increase of undercooling, the immiscible effect is strengthened and liquid separation occurs, which forms Co-rich and Cu-rich regions. As for Co70Cu30 alloy undercooled by 237 K and Co50Cu50 alloy undercooled by 188 K, the influence of solute content on rapid solidified microstructure is weakened, which can be inferred from the almost same of the grain size and solute concentration. Moreover, liquid separation proceeds more completely for Co50Cu50 alloy due to the sufficient duration time for immiscible stage arising from the lower critical immiscible undercooling.
Key words: immiscible alloy; non-equilibrium solidification; grain refinement; phase transformation kinetics
