Zr-4合金中氢化物析出长大的透射电镜原位研究

用透射电子显微镜拉伸试样台原位研究了应力、电子束辐照以及第二相对Zr-4合金中氢化物析出和长大的影响。结果表明,在拉应力作用下,裂纹易于沿氢化物扩展,并在裂尖垂直于拉应力方向析出新的氢化物。氢化物在拉应力诱发下的析出、开裂、再析出·····过程,导致了氢致延迟开裂。在较强的会聚电子束辐照下,Zr-4合金中的氢化物会分解,新的氢化物会围绕着附近的Zr(Fe,Cr)2第二相粒子析出,新析出的氢化物为面心立方结构的δ相。

In Situ Investigation of Hydride Precipitation and Growth in Zircaloy-4 by Transmission Electron Microscopy

The effects of stress,electron beam irradiation and second phase particles on zirconium hydride precipitation and growth in Zircaloy-4 were investigated using in-situ transmission electron microscope observation.Results show that with the tensile stress the cracks are likely to propagate along hydrides and new hydrides are formed at the crack tip along the vertical direction of the applied stress.A process of precipitation,cracking,re-precipitation and so on,induced by tensile stress,causes delayed hydride cracking (DHC).Under the high irradiation of converged electron beam,the hydrides decompose in the Zircaloy-4,and new hydrides prefer to precipitate around the unoxidized Zr(Fe,Cr)2 particles,and the re-precipitated hydrides are fcc-structure δ phase.