Papers by Author: Tao Yu

Abstract: The optimal geometries and mechanical properties of a kink with P are studied by applying density functional theory to the ½[111](1¯10) edge dislocation in bcc iron. The calculated impurity segregation energy shows that the P atom can be potentially trapped by the kink, and the doping P preferably segregates to the core region of the ½[111](1¯10) edge dislocation rather than to the <100>(010) edge dislocation. The analysis of the electronic structure indicates that the sideward motion of the kink is impeded owing to strong a interaction between P and neighboring Fe atoms. That is, the P induces a pinning effect on the ½[111](1¯10) edge dislocation. The hybridizations between P and Fe come from P 3p and Fe 3d4s4p. The p and d states have an obvious orientation, which may not be favorable to the toughness of iron. The localized effect of the P-kink complex distinctly affects the electronic structure as well as the energy of the system.

Abstract: Ultrafine-grained treatment (multiple forging and heat treatment) were carried out on FGH4096 alloy to get ultrafine grain with grain being of 1-5μm. OM, SEM, TEM and tensile test were used to study the action of ultrafine-grained treatment on improving structure and properties. The tensile properties of the alloy processed under ultrafine-grained treated have shown quite satisfactory levels, which ultimate strength (UTS) reach 1730Mpa and yield strength (YS) values reach 1470Mpa at room temperature. The apperance of advanced strength has originated chiefly form not only the persence of fine grains, but also structure of grain boundaries and diaperce pricipitations of secondary phase. A better combination of mechanical properties achieved by use of ultrafine-grained treatment makes it possible to explore the dual property turbine disc to its maximum potential for FGH 4096 alloy.