High Temperature Stress-Rupture Properties of TiAl Base Alloy Directionally Solidified by Cold Crucible Method
DING Hongsheng1, LI Jintao1, WANG Qiang1, GENG Hongbin2, CHEN Ruirun1,GUO Jingjie1, FU Hengzhi1
(1. National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001, China;
2. National Defense Science and Technology Key Lab for Space Materials Behavior and Evaluation,
Harbin Institute of Technology, Harbin 150001, China)
Abstract：In this paper, TiAl 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 withdrawal
rate and thinner inter-lamellar spacing was achieved at higher withdrawal rate. The included angels between columnar
crystal orientation and the growth direction increase with the increasing withdrawal rate. The high temperature tensile
properties were tested from 600℃ to 800℃ and the fracture strength of the alloy decreased with the increasing test temperature.
Inter-lamellar spacing was a significant influence factor on the high temperature tensile strength and the alloy prepared
at withdrawal rate of 1.2mm/min showed the highest strength (470MPa) at 800℃ . The α2/γ interfaces in the fully lamellar
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/650℃ . The results showed that finer inter-lamellar spacing could enhance the high temperature stress ruptureproperties.
Under the same test conditions, the alloy prepared at withdrawal rate of 1.2mm/min held the highest creeprupture
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 ductile fracture. The predication model of the stressrupture
was set up through Larson-Miller and Manson-Haferd parametric method. The predication function is an accurate
model confirmed by little difference existing between theoretical and experimental values.
丁宏升，李金韬，王 强，耿洪滨，陈瑞润，郭景杰，傅恒志. 冷坩埚定向凝固TiAl基合金高温持久性能研究*[J]. 航空制造技术, 2016, 59(23/24): 36-41.
DING Hongsheng1, LI Jintao1, WANG Qiang1, GENG Hongbin2, CHEN Ruirun1,GUO Jingjie1, FU Hengzhi1. High Temperature Stress-Rupture Properties of TiAl Base Alloy Directionally Solidified by Cold Crucible Method. Aeronautical Manufacturing Technology, 2016, 59(23/24): 36-41.
2016, 
