冷坩埚定向凝固TiAl基合金高温持久性能研究  

High Temperature Stress-Rupture Properties of TiAl Base Alloy Directionally Solidified by Cold Crucible Method

作　　者：丁宏升[1] 李金韬 王强[1] 耿洪滨[2] 陈瑞润[1] 郭景杰[1] 傅恒志[1] 

机构地区：[1]哈尔滨工业大学金属精密热加工国家级重点实验室,哈尔滨150001 [2]哈尔滨工业大学空间环境材料行为与评价技术国家级重点实验室,哈尔滨150001

出　　处：《航空制造技术》2016年第23期34-41,47,共9页Aeronautical Manufacturing Technology

基　　金：国家自然科学基金项目(51171053,51471062);国家重点基础研究发展计划(973)项目(2011CB605504)

摘　　要：采用电磁冷坩埚定向凝固技术制备了成分为Ti-47Al-2Cr-2Nb的合金铸锭，定向凝固后的显微组织为α2＋γ全片层结构。在0．4-1．2mm／min的抽拉速率范围内，随着抽拉速率的增加，片层间距减小，柱状晶与生长方向的夹角增大。随着温度升高，合金的拉伸强度有所下降，但由于细化片层界面对切变应力变形的阻碍作用，合金的高温拉伸强度会随着抽拉速率的增加而提高。通过对抽拉速率为1．0mm／min试样的拉伸强度与温度的拟合，得到了拉伸强度和温度之间的函数关系。随着抽拉速率的增加，Ti-47Al-2Cr-2Nb合金的持久寿命明显升高，对于抽拉速率为1．2mm／min试样的持久性能测试表明，其持久寿命最长，达到了48h。持久试样的断口形貌表明，其断裂的主要方式是伴随着少量延性断裂的脆性解理断裂。最后根据时间一温度模型，分别采用Larson-Miller和Manson—Haferd参数法建立了定向凝固Ti-47Al-2Cr-2Nb合金的持久强度预测函数模型，预测的理论值与试验结果吻合度较高。In this paper, TiAI based alloy with composition of Ti-47Al-2Cr-2Nb has been successfully prepared by electromagnetic cold crucible directional solidification. The microstructure of the directionally solidified alloy consisted of alternatively arranged lamellae which were composed of α2＋γ laths. The inter-lamellar spacing was influenced by with- drawal rate and thinner inter-lamellar spacing was achieved at higher withdrawal rate. The included angels between colum- nar crystal orientation and the growth direction increase with the increasing withdrawal rate. The high temperature tensile properties were tested from 600℃ to 8000℃ and the fracture strength of the alloy decreased with the increasing test tem- perature. Inter-lamellar spacing was a significant influence factor on the high temperature tensile strength and the alloy pre- pared at withdrawal rate of 1.2ram/rain showed the highest strength （470MPa） at 800℃ . The α2＋γ interfaces in the fully la- mellar structure could act as obstacles to shearing. Higher density of interfaces existed in the matrix of the alloy with higher withdrawal rates and greater applied stress was essential for further deformation in case of thinner inter-lamellar spacing. A function of tensile strength and test temperature was created according to the values of alloy prepared at withdrawal rate of 1.0 mm/min from 600℃ to 800℃ . The effect of withdrawal rate on the stress rupture-properties was investigated at 200MPa/6500℃. The results showed that finer inter-lamellar spacing could enhance the high temperature stress rupture- properties. Under the same test conditions, the alloy prepared at withdrawal rate of 1.2mm/min held the highest creep- rupture life （48h）. The improvement effect of thinner lamellar structure on creep-rupture life decreased with the increasing test temperature and applied stress. The fracture morphology of the stress-rupture samples indicated the Ti-47Al-2Cr-2Nb behaved in brittle cleavage fracture companied with a small amount of duct

关 键 词：TIAL基合金 定向凝固 冷坩埚 高温拉伸性能 持久性能 

分 类 号：V252[一般工业技术—材料科学与工程]