Subsequently, fracture surfaces and helium bubble evolution were studied in detail by SEM and TEM observations, respectively. In addition, post He-implantation creep tests were conducted at 650 ☌ as well. The average temperature was controlled to 650 ☌ within ☒ ☌. Helium ions of energies varying from 0 to 25 MeV were implanted at a rate of 6 × 10 −3 appm/s (corresponding to a displacement dose rate of 1.5 × 10 −6 dpa/s). In-situ creep was performed in an in-beam creep device under uniaxial tensile stresses from 350 to 370 MPa during homogeneous helium implantation. In the present paper, the effects of helium on creep properties of Fe–14CrWTi ODS steel were studied by in-beam and post He-implantation creep tests. The energy dispersive X-ray spectrometry elemental and high resolution transmission electron microscopy analysis suggest that the stabilizing mechanisms of the Y 2O 3 particles involve both the segregation of Ti atoms to the surface layers of large Y 2O 3 particles and dissolution of Ti atoms into small Y 2O 3 particles to form complex particles. The different microstructural features of the two extruded samples lead to distinctively different mechanical behaviors and electrical conductivities. However, a heterogeneous Cu matrix microstructure, consisting of elongated micrometer-scale Cu grains and equiaxed ultrafine Cu grains, is observed in the Ti-free sample due to significant coarsening of the Y 2O 3 particles. It is found that the addition of a small amount of 0.4 wt.%Ti effectively suppresses the coarsening of Y 2O 3 particles during material fabrication, which produces smaller and more uniform oxide particles distributed in a homogeneous ultrafine grained Cu matrix. In this work, high volume fraction Y 2O 3 dispersion strengthened Ti-free and Ti-doped Cu samples were prepared by mechanical alloying, high temperature heat treatment and powder compact extrusion to study the role of alloying Ti element on microstructures, mechanical properties and electrical conductivity of the extruded samples.
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