Ti/Al比对GH984G合金长期时效过程中γ′沉淀相粗化行为及拉伸性能的影响
谭梅林, 女, 1988年生, 硕士生
收稿日期: 2014-03-24
修回日期: 2014-03-24
录用日期: 2014-08-19
网络出版日期: 2014-10-28
基金资助
* 国家高技术研究发展计划项目 2012AA03A501, 国家自然科学基金项目 51301171, 国家能源局项目 NY20110102-1和中国科学院-四川省成果转化项目资助
INFLUENCE OF Ti/Al RATIOS ON γ′ COARSENING BEHAVIOR AND TENSILE PROPERTIES OF GH984G ALLOY DURING LONG-TERM THERMAL EXPOSURE
Received date: 2014-03-24
Revised date: 2014-03-24
Accepted date: 2014-08-19
Online published: 2014-10-28
Supported by
Supported by National High Technology Research and Development Program of China (No.2012AA03A501), National Natural Science Foundation of China (No.51301171), National Energy Administration Program of China (No.NY20110102-1) and Chinese Academy of Sciences and Sichuan Province Cooperation Program
研究了2种Ti/Al比对新型Ni-Fe-Cr基合金GH984G在长达上万小时高温时效过程中γ′淀相的粗化行为及其拉伸性能的影响规律. 结果表明: 随时效温度从700 ℃升高至800 ℃, 球形γ′沉淀相的粗化速率明显增大. 在700和750 ℃长期时效过程中, 高Ti/Al比和低Ti/Al比合金γ′沉淀相的粗化行为均符合Lifshitz-Slyozof-Wagner (LSW) 理论, 受扩散过程控制, 高Ti/Al比合金中γ′沉淀相的粗化速率较高. 800 ℃长期时效过程中, 2种Ti/Al比合金γ′沉淀相的粗化行为偏离LSW理论. 此外, 时效时间小于3×103 h时, 高Ti/Al比合金的γ′沉淀相长大较快, 进一步延长时效时间, 低Ti/Al比合金的γ′沉淀相长大速率较快. Ti/Al比对合金标准热处理态和700~800 ℃时效10480 h后合金的700 ℃拉伸性能无明显影响. 通过选取合适的Ti/Al比, 可以控制γ′沉淀相的粗化行为, 增强合金组织稳定性.
关键词： Ni-Fe-Cr基合金; 长期时效; γ′沉淀相; 粗化行为; 拉伸性能
谭梅林 , 王常帅 , 郭永安 , 郭建亭 , 周兰章 . Ti/Al比对GH984G合金长期时效过程中γ′沉淀相粗化行为及拉伸性能的影响[J]. 金属学报, 2014 , 50(10) : 1260 -1268 . DOI: 10.11900/0412.1961.2014.00137
GH984G is a new Ni-Fe-Cr base alloy which has been designed for use as superheater, reheater and header materials for boilers in 700 ℃ advanced ultra-supercritical (A-USC) coal-fired power plants. Compared with the CCA617, Nimonic 263 and IN 740 alloys, the GH984G is an economic alloy due to the elimination of Co and it containing more than 20%Fe. As a precipitation hardened alloy, the size of γ′ precipitates has great influence on the tensile properties. The γ′ precipitates become coarse during long-term thermal exposure. The coarsening behavior of γ′ precipitates is closely related with Ti/Al ratio. However, there are few investigations about the influence of Ti/Al ratio on the coarsening behavior of γ′ precipitates of GH984G alloy. Therefore, in this work, the coarsening behavior of γ′ precipitates and its influence on tensile properties of GH984G alloy with two Ti/Al ratios was investigated during long-term thermal exposure. The results show that the growth kinetic of the γ′ precipitates can be explained by Lifshitz-Slyozov-Wagner's theory of element diffusion controlled coarsening during long-term thermal exposure at 700 and 750 ℃. The rate of γ′ precipitates growth of the alloy with high Ti/Al ratio is higher. At 800 ℃, the rate of γ′ precipitates growth decreases with increasing the thermal exposure time. The coarsening behavior does not follow the Lifshitz-Slyozov-Wagner's theory. The reasons are attributed to the effect of elastic interaction energy and the depletion of γ′-forming elements in γ matrix. The Ti/Al ratio has no obvious influence on 700 ℃ tensile properties during long-term thermal exposure between 700 and 800 ℃. The 700 ℃ yield strength has no obviously decreases even if after thermal exposure at 700 ℃ for 10480 h. The ductility increases after thermal exposure at 800 ℃. The variation of strength and ductility is attributed to the coarsening of γ′ precipitation. The deformation mechanism is the moving dislocations shear γ′ precipitates and the stacking faults form in γ′ precipitates. The fracture mode is the mixture fracture mode. The Ti/Al ratio has no significance influence on the deformation mechanism and the fracture mode.
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