(1. 中南大學(xué) 輕合金研究院，長沙 410083； 2. 桂林航天工業(yè)學(xué)院，桂林 541004； 3. 中南大學(xué) 粉末冶金國家重點實驗室，長沙 410083； 4. 北京宇航系統(tǒng)工程研究所，北京100076)
摘 要: 采用超聲半連續(xù)鑄造方法制備了d 1250mm大規(guī)格2219鋁合金鑄錠，并通過光譜儀、OM、SEM、拉伸試驗等手段研究了大鑄錠成分偏析現(xiàn)象及多向鍛-固溶時效熱處理對鑄錠組織和性能的影響。結(jié)果表明，沿鑄錠徑向方向合金的凝固冷卻速度波動較大，導(dǎo)致主合金元素產(chǎn)生嚴(yán)重的宏觀偏析，從而促使中心部非平衡結(jié)晶相Al2Cu數(shù)量較多且枝晶粗大，愈往邊部非平衡結(jié)晶相數(shù)量逐漸減少，枝晶也呈減薄趨勢。經(jīng)多級均勻化和多向鍛-固溶時效熱處理后，(2/3~5/6)半徑處綜合性能最優(yōu)，軸向和徑向性能基本一致，強度分別為420 MPa、323 MPa，伸長率為8.7%，切向強度分別為448 MPa、343 MPa，伸長率為11.0%。從邊部到中心部，2219合金的拉伸斷裂由韌性斷裂為主逐漸過渡到以脆性斷裂為主。可見，由于凝固速度造成的大鑄錠的偏析現(xiàn)象可以通過多向鍛-固溶時效熱處理手段加以改善。
關(guān)鍵字: 大規(guī)格鑄錠；2219合金；成分偏析；多向鍛-固溶時效熱處理；組織演變；力學(xué)性能
（1. Light Alloy Research Institute, Central South University, Changsha 410083, China; 2. Guilin University of Aerospace Technology, Guilin 541104, China; 3. State Key Laboratory of Powder Metallurgy，Central South University, Changsha 410083, China; 4. Beijing Institute of Astronautical Systems Engineering, Beijing 100076, China）
Abstract:The composition segregation behavior of 2219 aluminum alloy produced by ultrasonic semi-continuous ingot with diameter of 1250 mm and the effect of multi-axial forging and solution-aging on microstructure and mechanical properties of 2219 aluminum alloy were investigated by spectrograph, optical microscopy, scanning electron microscopy and tensile testing. The results show that the main alloy element along the radial of casting has serious segregation under the volatile cooling rate, which impels non-uniform distribution of non-equilibrium crystallization phase Al2Cu. The billet core has higher numbers of Al2Cu phase and dendrites are coarse. The non-equilibrium crystallization phase reduces gradually and the dendrites refines obviously from the core to the edge. After being treated by multi-stage homogenization and multidirectional forging-solution and aging treatment, the area between 2/3 and 5/6 of ingot radius has the best comprehensive mechanical properties with the tensile strength of 420 MPa (axial and radial directions) and 448 MPa (tangent direction), the yield strength of 323 MPa (axial and radial directions) and 343 MPa (tangent direction), and the elongation of 8.70% (axial and radial directions) and 11.0% (tangent direction). The main fracture mechanisms of 2219 alloy will make the transition from ductile fracture to brittle fracture along the radial of casting. Therefore, multidirectional forging-solution and aging treatment is an effective means to weaken the macro-segregation.
Key words: large-scale ingot; 2219 alloy; composition segregation; multidirectional forging-solution and aging treatment; microstructure evolution; mechanical properties
