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徐 平光; Yin, J*; Zhang, S. Y.*
Acta Metallurgica Sinica, 51(11), p.1297 - 1305, 2015/11
The tensile deformation behavior of 1250 MPa ultra-high strength steels with and without hydrogen charging was comparably investigated using neutron diffraction together with the fracture morphology and microstructure observation. Before tensile loading, the (110) lattice spacing of hydrogen charged steel was found larger than that of non-charged sample while the (200) lattice spacing of the former was smaller than that of the latter, suggesting that the hydrogen atoms occupied the tetrahedral center promoted the increment of lattice plane spacing of (110) crystal planes while the balanced internal stress resulted in the proper decrement of (200) lattice plane spacing. In the non-charged sample, the non-linear elastic deformation was observed at 700 MPa in (200) planes, and then at 800 MPa in (110) planes. In the hydrogen charged sample, the non-linear elastic deformation was observed at 300 MPa in (110) planes, and then at 400 MPa in (200) planes. The microstructure observation confirmed the cleavage crack propagation and local crystal rotation in the hydrogen charged sample. Here, a concept about crystallographic orientation dependent micro-yielding was proposed, i.e. the hydrogen charging promoted the (110) preferable micro-yielding rather than (200) preferable micro-yielding, and resulted into a special deformation characteristics.
倉田 有司; 内海 宏和*
Acta Metallurgica Sinica (English Letters), 11(6), p.397 - 404, 1998/12
Ni-18.5Cr合金の正常型クリープ曲線及びNi-18.5Cr-16W合金の3次クリープ支配型クリープ曲線に対して、次のようなクリープ構成式の適用性を検討した。(1)修正法、(2)修正法、(3)投影法、(4)3次クリープのみの2法、(5)法。この研究で新しく提案したのは、(1)、(2)及び(4)である。(1)では1次クリープを指数項、3次クリープを対数項で表し、(2)ではクリープ曲線を2つの対数項の和で表している。修正法、修正法、投影法では正常型及び3次クリープ支配型のクリープ曲線を記述できた。また、900CのNi-18.5Cr-16W合金のクリープ曲線は、2法及び法によっても記述された。修正法及び修正法は、破断までのクリープ曲線や破断寿命をより精度よくかつ保守的に予測できるため、定荷重クリープ曲線に対しては、この2つの方法の適用性が高い。