TENSILE DEFORMATION BEHAVIOR OF HYDROGEN CHARGED ULTRAHIGH STRENGTH STEEL STUDIED BY IN SITU NEUTRON DIFFRACTION

Abstract

The tensile deformation behavior and the axial lattice strain response of 1250 MPa ultrahigh strength steels with and without hydrogen charging were comparably investigated using time-of-flight neutron diffraction together with the fracture morphology and microstructure observation. Before tensile loading, the axial (110) lattice plane spacing of hydrogen charged specimen was found larger than that of noncharged specimen while the axial (200) lattice plane spacing of the former was smaller than that of the latter, suggesting that the hydrogen atoms occupied the tetrahedral site promoted the increment of axial (110) lattice plane spacing while the balanced internal stress resulted in the proper decrement of axial (200) lattice plane spacing. The necking and ductile fracture after approaching the 1250 MPa tensile strength occurred in the non-charged specimen, while the brittle *收到初稿日期: 2014-09-30,收到修改稿日期: 2015-07-18 作者简介:徐平光,男, 1973年生,研究副主干,博士 DOI: 10.11900/0412.1961.2014.00541 第1297-1305页 pp.1297-1305