摘要
研究了镍基GH738高温合金经两种热处理后分别在550、750、800和850℃下,时效0～4500 h后γ'强化相形貌与硬度性能之间的关联性。结果表明,在长期时效过程中,经两种热处理后,γ'强化相随温度升高和时间延长而长大,但温度比时间影响更明显;γ'相粗化速率随着时效温度的升高和γ'相初始尺寸的增大而增大;γ'相的粗化符合L-S-W熟化理论;长期时效中γ'相的长大初期粗化速率较高;经过550℃长期时效后组织及性能几乎没有变化,表明合金在该温度下具有良好的组织稳定性;同时获得两种热处理后长期时效γ'相长大激活能;两种热处理制度下,时效硬度随温度变化大致呈下降趋势,亚固溶热处理后合金时效硬度明显高于过固溶热处理后的硬度;同时发现在750、800和850℃温度下,随着温度升高合金强化相的数量逐渐降低,从而导致合金强化相体积分数的降低。
Influence of temperature and time on microstructure of GH738 superalloy after long time ageing was investigated. The alloy was subjected to aging heat treatment at four different temperatures ranging from 550 ℃ to 850 ℃ for different time ranging from 0-4500 h after supersolvus and subsolvus heat treatment. The microstructure evolution was characterized by optical microscopy and field emission scanning electron microscopy. The results show that strengthening γ＇ phase grows up with in creasing temperature and time, and the effect of aging temperature is more obvious than aging time for the growth rate of γ＇ phase. The coarsening rate of γ＇ phase gradually increases with the increasing of temperature and initial γ＇ phase size, which obeys L-S-W aging theory. The growth rate of γ＇ phase in the early stages is higher than that in later stage. Mierostructure and properties of the alloy after long-time aging at 550 ℃ exhibit little changes, indicating that GH738 superalloy has excellent structure stability at 550 ℃. The primary and secondary γ＇ phases coarsening activation energies for supersolvus and subsolvus heat treatment could be calculated, and hardness after long time aging for subsolvus heat treatment is obviously higher than that for superaolvus heat treatment and hardness after long time aging decreases with increasing temperature for both supersolvus and subsolvus heat treatment. Besides, the results show that volume fraction of γ＇ phase is decreased when ageing temperature increases from 750 ℃ to 850 ℃.
出处
《材料热处理学报》
EI
CAS
CSCD
北大核心
2013年第1期31-37,共7页
Transactions of Materials and Heat Treatment
基金
国家自然科学基金(51071017)
