退火对热老化308L不锈钢焊材显微结构的影响
Effect of Annealing on Microstructure of Thermally Aged 308L Stainless Steel Weld Metal
查看参考文献54篇
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文摘
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对410℃下热老化7000h的308L不锈钢焊材进行了550 ℃、1h的退火处理,利用TEM和三维原子探针研究了退火对热老化焊材显微结构的影响,并与未热老化试样进行比较,评价退火回复效果。结果表明,退火后奥氏体无明显变化,而δ铁素体内由热老化导致的调幅分解完全消失,且G相显著减少。此外,热老化导致Ni、Mn、C在δ铁素体/奥氏体相界处发生偏聚,而对相界处Cr、Si、P元素的含量无明显影响。退火后相界处所有元素均无偏聚,但会导致Ni、Mn在靠近相界的奥氏体一侧发生富集。退火后308L不锈钢焊材的显微结构接近于未热老化状态,表明退火回复效果显著。 |
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其他语种文摘
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Austenitic stainless steel weld metal has been widely used as nozzle/safe-end joint and inner surface cladding of reactor pressure vessel, due to its good mechanical property and corrosion resistance. However, long-term thermal ageing at the service temperature (280-330℃) could induce hardening and embrittlement of the weld metal. To recover the thermal ageing embrittlement, the annealing treatment has been proposed since the annealing could affect the ageing-induced microstructural changes such as spinodal decomposition and G-phase precipitation in ferrite. However, there is still an incomplete understanding as well as a lack of nanoscale investigation about the annealing effect on the microstructural change of the weld metal. In this work, 308L stainless steel weld metal was thermally aged at 410 ℃for 7000 h, followed by an annealing treatment at 550 ℃ for 1 h. Since the weld metal has a dual-phase structure of austenite and δ-ferrite, the phase transformation of austenite and δ-ferrite as well as the ele ment segregation at the δ-ferrite/austenite phase boundary were investigated by TEM and atom probe tomography. The results revealed that austenite was unaffected by annealing while the ageing-induced spinodal decomposition of δ-ferrite was completely recovered. In addition, the number density of G phase in δ-ferrite was significantly reduced following annealing. This indicates that austenite has a higher stability compared with δ-ferrite. As for the δ-ferrite/austenite phase boundary, thermal ageing induced the segregation of Ni, Mn and C at the phase boundary, while the contents of Cr, Si and P remained almost unchanged. Following the annealing treatment, the segregation of all elements was eliminated. Further, only a small quantity of Ni and Mn was enriched in austenite near the phase boundary. The results suggested that the microstructure of the annealed specimen was similar to that of the unaged specimen, indicating a good recovery of the microstructure by annealing. |
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来源
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金属学报
,2019,55(5):555-565 【核心库】
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DOI
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10.11900/0412.1961.2018.00365
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关键词
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不锈钢焊材
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热老化
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退火
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调幅分解
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G相析出
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相界偏聚
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地址
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1.
中国科学院金属研究所, 中国科学院核用材料与安全性评价重点实验室, 沈阳, 110016
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中国科学技术大学材料科学与工程学院, 沈阳, 110016
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苏州热工研究院有限公司, 苏州, 215004
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语种
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中文 |
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文献类型
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研究性论文 |
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ISSN
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0412-1961 |
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学科
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金属学与金属工艺 |
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基金
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国家自然科学基金项目
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文献收藏号
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CSCD:6488959
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