Grain Boundary Engineering for Control of Fatigue Fracture in 316L Austenitic Stainless Steel
Grain Boundary Engineering for Control of Fatigue Fracture in 316L Austenitic Stainless Steel
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DOI：
10.2320/matertrans.mb201804
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发表时间：
2019-01-01
影响因子：
1.2
通讯作者：
Tsurekawa, Sadahiro
中科院分区：
文献类型：
--
作者：
Kobayashi, Shigeaki;Ogou, Satoshi;Tsurekawa, Sadahiro
研究了晶界在316L奥氏体不锈钢疲劳裂纹形核和扩展中的作用，为控制高周疲劳断裂的晶界工程提供了线索。当低应力幅值小于160 Mpa时，疲劳裂纹优先在晶界形核。特别是，82%的裂纹晶界是随机晶界。疲劳裂纹在随机边界上的形核与晶界面应力轴的几何构型以及相邻晶界上的持久滑移带(PSB)无关。虽然疲劳裂纹即使在退火孪晶界，即{111}/Sigma3重合点阵晶界也有形核，但只有当Sigma3CSL晶界的表面轨迹平行于相邻晶内的PSB时，才会发生裂纹形核。此外，对疲劳裂纹扩展的现场观察表明，晶界起着裂纹路径、裂纹偏转位置和裂纹扩展障碍的重要作用，这取决于晶界的性质。特别是，虽然Sigma 3 CSL边界成为裂纹扩展路径，但当裂纹沿Sigma 3 CSL边界扩展时，裂纹扩展速率局部降低。另一方面，当裂纹沿随机边界扩展时，裂纹扩展速率显著增加。论证了晶界工程在控制高周疲劳断裂中的作用。316L不锈钢中CSL晶界含量越高，疲劳强度越高，疲劳寿命越长。
Roles of grain boundaries in fatigue crack nucleation and propagation in 316L austenitic stainless steel were investigated to obtain a clue to the grain boundary engineering for control of high-cycle fatigue fracture. The fatigue crack nucleation preferentially occurred at grain boundaries at the low-stress amplitude conditions less than about 160 MPa. In particular, the 82% of cracked grain boundaries were random boundaries. The fatigue crack nucleation at the random boundaries occurred irrespective of the geometrical configuration of grain boundary plane to the stress axis and the persistent slip bands (PSBs) in the neighboring grains. Although the fatigue cracks nucleated even at the annealing twin boundaries, namely the {111}/Sigma 3 coincidence site lattice (CSL) boundaries the crack nucleation occurred only when the surface trace of the Sigma 3 CSL boundaries was parallel to the PSBs in the neighboring grains. Moreover, in-situ observations of the fatigue crack propagation revealed that the grain boundaries played important roles as crack path, crack deflection sites and barrier of crack propagation, depending their character. In particular, although the Sigma 3 CSL boundaries became crack propagation path, the crack propagation rate locally decreased when the crack propagated along the Sigma 3 CSL boundaries. On the other hand, the crack propagation rate considerably increased when the crack propagated along random boundaries. The usefulness of grain boundary engineering for control of high-cycle fatigue fracture was demonstrated. The higher fraction of CSL boundaries achieved higher fatigue strength and longer fatigue life in 316L stainless steel.