时效处理对20%冷变形15Cr-15Ni含Ti奥氏体不锈钢组织和高温力学性能的影响

Influence of Aging Treatment on the Microstructure and High Temperature Mechanical Properties for 15Cr-15Ni Titanium-modified Austenitic Stainless Steel in 20% Cold-worked Condition

摘要:

针对钠冷快堆包壳管用15Cr-15Ni含Ti的奥氏体不锈钢,研究了550-750℃时效处理336h对20%冷变形合金组织和650℃拉伸性能的影响。结果表明：在550℃时效336h后,合金发生回复,组织中位错移动产生大量退火孪晶。当在650℃和750℃时效时,合金进一步回复,孪晶数量明显减少,且在组织中发现有Sigma相析出。随时效温度的升高,sigma相数量和尺寸增加。与20%冷变形合金650℃拉伸性能相比,550℃时效态样品拉伸时,合金屈服和抗拉强度略有增加；随着时效温度的升高,合金屈服和抗拉强度显著降低。与拉伸强度相比,时效态合金的延伸率变化趋势与之相反,时效温度升高,合金的延伸率提高。

Abstract:

Titanium-stabilized 15Cr-15Ni austenitic stainless steel in 20% cold-worked condition has been considered as a promising candidate high temperature structural material for core components in liquid metal-cooled fast reactors (LMFR). Microstructure and high temperature mechanical properties of as cold-worked and different aging treatments alloys were investigated by using metallographic microscope, scanning and transmission electron microscope, and tensile testing machine. The results demonstrate that the recovery took place when the alloys were aged at 550℃ for 336h. The emergence abundant of twins was attributed to dislocations movement. When aging temperature increasing to 650℃ and 750℃, the amount of twins reduced because of alloy′s further recover. Sigma phase precipitated from austenitic matrix along grain boundaries when alloys were aged at 650-750℃ for 336h. The amount and size of sigma phase increased with the aging temperature and time increasing. Because of the grain boundary strengthening, alloys aged at 550℃ had slightly higher yield strength and ultimate tensile strength than those of as-cold worked alloy. The high temperature yield strength and ultimate tensile strength decreased significantly, while plasticity increased observably when aging temperature increasing to 650℃ and 750℃.