Effect of Ce addition on secondary phase transformation and mechanical properties of 27Cr–7Ni hyper duplex stainless steels
Effect of Ce addition on secondary phase transformation and mechanical properties of 27Cr–7Ni hyper duplex stainless steels
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DOI：
10.1016/j.msea.2013.02.044
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发表时间：
2013-06
期刊：
影响因子：
6.4
通讯作者：
Sun Mi Kim;Ji Soo Kim;K. Kim;Kyung-Tae Park;C. Lee
中科院分区：
文献类型：
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作者：
Sun Mi Kim;Ji Soo Kim;K. Kim;Kyung-Tae Park;C. Lee
研究了Ce对27 Cr-7 Ni-2.5Mo-3.3W超双相不锈钢σ、χ第二相转变行为及力学性能的影响。对四种不同Ce含量（0、55、110和450 ppm）的钢进行固溶热处理，然后在873- 1273 K温度范围内等温退火1- 1000 min。在固溶热处理钢中，第二相没有形成，抗拉强度略有增加，在Ce添加试样，但夏比冲击韧性变化取决于夹杂物的尺寸和体积分数。随后的等温退火导致所有钢中第二相的析出。当Ce的加入量为55和110 ppm时，由于Ce的均匀分布，沉淀过程明显延迟。另一方面，在高Ce含量（450 ppm）的钢中，形成富Ce颗粒，导致基体中的Ce浓度极低，这不能阻止第二相的析出。σ相（1%）或χ相（0.5%）析出的时间-温度转变图与钢的50%韧性下降曲线吻合较好。得出的结论是，最佳的Ce浓度与其在基体中的均匀分布是最有效的，在延迟形成的第二相，因此，以防止机械性能的退化。
This study aims to investigate the effects of Ce addition on the transformation behavior of σ and χ secondary phases and corresponding mechanical properties of 27Cr–7Ni–2.5Mo-3.3W hyper duplex stainless steels. Four different steels containing various Ce content (0, 55, 110 and 450ppm) were subjected to solid-solution heat treatment and subsequent isothermal annealing at temperature range of 873–1273K for 1–1000min. In the solid-solution heat-treated steels where secondary phases were not formed, tensile strength was slightly increased in the Ce added specimens, but Charpy impact toughness varied depending on the size and volume fraction of inclusion. Subsequent isothermal annealing resulted in the precipitation of secondary phases in all steels. However, when a small amount (55 and 110ppm) of Ce was added, precipitation was considerably delayed which was attributed to the homogeneous distribution of Ce. On the other hand, in the high (450ppm) Ce content steel, Ce-rich particles were formed resulting in extremely low Ce concentration in the matrix, which could not retard the precipitation of secondary phases. Time–temperature transformation diagram for the precipitation of either σ (1%) or χ phase (0.5%) was well matched with the 50% toughness reduction curve of the steel. It was concluded that optimum Ce concentration with its homogeneous distribution in the matrix is the most effective at retarding the formation of secondary phases and therefore to prevent the degradation of mechanical properties.