CAJ | 학술논문

在3～70μm/s的生长速度范围内对Ti-46Al-8Nb(摩尔分数,％)合金进行定向凝固实验,研究其微观组织演变和微观偏析形式.在该生长速度范围内,固-液界面表现为规则的枝晶生长,一次枝晶间距随着生长速度的加快而逐渐减小.在定向凝固过程中观察到典型的L+β→α包晶反应,最终得到具有α2/γ层片和B2相的微观组织.在各个晶粒中,层片与β相枝晶初始生长方向呈0或45°.包晶反应导致严重的成分偏析,在凝固过程中,铝富集在枝晶间,铌富集在枝晶心部.随着α相的形核和生长,铌的偏析程度逐渐增大,从而促进B2相的析出,而富集在枝晶间的铝在包晶反应发生后逐渐变得均匀、一致.
재3～70μm/s적생장속도범위내대Ti-46Al-8Nb(마이분수,％)합금진행정향응고실험,연구기미관조직연변화미관편석형식.재해생장속도범위내,고-액계면표현위규칙적지정생장,일차지정간거수착생장속도적가쾌이축점감소.재정향응고과정중관찰도전형적L+β→α포정반응,최종득도구유α2/γ층편화B2상적미관조직.재각개정립중,층편여β상지정초시생장방향정0혹45°.포정반응도치엄중적성분편석,재응고과정중,려부집재지정간,니부집재지정심부.수착α상적형핵화생장,니적편석정도축점증대,종이촉진B2상적석출,이부집재지정간적려재포정반응발생후축점변득균균、일치.
Directional solidification experiments were conducted for Ti-46Ak-8Nb alloy at the growth rates ranging from 3 to 70μm/s.The microstructure evolution and microsegregation pattern were investigated.In the range of growth rate,a regular dendritic structure appears and the primary dendrite spacing decreases with increasing growth rate.The peritectic reaction is observed during the solidification and the final microstructure is composed of α2/γlamellar structure and retained β(B2) after directional solidification.The lamellar orientation is found to be parallel and 45° to the primary growth direction ofβ dendrite.Peritectic reaction leads to significant chemical inhomogeneity,in which aluminum is rich in interdendritic liquid and niobium is rich in the core ofβ dendrite during the solidification.With the nucleation and growth of α phase,the segregation amplitude of niobium increases,which promotes the formation of B2 phase,while aluminum rich in the interdendritic becomes homogeneous gradually.