This study investigated the effect of thermal cycles on Cu-modified Ti64 thin-walled components deposited using the wire-arc directed energy deposition(wire-arc DED)process.For the samples before and after experiencin...This study investigated the effect of thermal cycles on Cu-modified Ti64 thin-walled components deposited using the wire-arc directed energy deposition(wire-arc DED)process.For the samples before and after experiencing thermal cycles,it was found that both microstructures consisted of priorβ,grain boundaryα(GBα),and basketweave structures containingα+βlamellae.Thermal cycles realized the refinement ofαlaths,the coarsening of priorβgrains andβlaths,while the size and morphology of continuously distributed GBαremained unchanged.The residualβcontent was increased after thermal cycles.Compared with the heat-treated sample with nanoscale Ti2Cu formed,short residence time in high temperature caused by the rapid cooling rate of thermal cycles restricted Ti2Cu formation.No formation of brittle Ti2Cu means that only grain refinement strengthening and solid-solution strengthening matter.The yield strength increased from 809.9 to 910.85 MPa(12.46%increase).Among them,the main contribution from solid solution strengthening(~51 MPa)was due to the elemental redistribution effect betweenαandβphases caused by thermal cycles through quantitative analysis.The ultimate tensile strength increased from 918.5 to 974.22 MPa(6.1%increase),while fracture elongation increased from 6.78 to 10.66%(57.23%increase).Grain refinement ofαlaths,the promotedα′martensite decomposition,decreased aspect ratio,decreased Schmid factor,and local misorientation change ofαlaths are the main factors in improved ductility.Additionally,although the fracture modes of the samples in the top and middle regions are both brittle-ductile mixed fracture mode,the thermal cycles still contributed to an improvement in tensile ductility.展开更多
Massive fracturing fluid injection in reservoir stimulation can alter the fluid pressure field,potentially inducing the faults to slip in an aseismic or seismic phenomenon.In this work,laboratory friction experiments ...Massive fracturing fluid injection in reservoir stimulation can alter the fluid pressure field,potentially inducing the faults to slip in an aseismic or seismic phenomenon.In this work,laboratory friction experiments were performed on split-cutting granite fracture to investigate the effect of fluid pressure on injection-induced slip behavior.The injection experiments spanned a fluid pressure range of 1-20 MPa,which was up to half of the confining pressure.The laboratory results demonstrated that an increase in confining pressure led to a marginal reduction in the friction coefficient,decreasing from a range of 0.70-0.80 at 10 MPa to 0.71-0.75 at 40 MPa.Friction constitutive parameters in experiments with fluid pressure above 10 MPa exhibited a transition from velocity-strengthening to velocity-weakening behavior,while remaining consistently velocity-strengthening below this threshold.Similarly,measurements of dilatancy and critical slip distance exhibited a similar evolution,first increasing and then becoming approximately constant,independent of fluid pressure.The observed microstructural evolution of the split-cutting fractures during slip testing supported these mechanical responses.Post-shear slip,a decrease in the fracture roughness and asperity distribution of the split-cutting fracture was noted,with the decrease in amplitude being more pronounced at high confining pressure.Research may provide a prospect on slip-on faults with fluid pressure.展开更多
基金sponsored by the National Key Laboratory Foundation of Science and Technology on Materials under Shock and Impact 2021ZX52002222019the Natural Science Foundation of China(NSFC No.U2141216)the Chongqing Technology Innovation and Application Special Program.
文摘This study investigated the effect of thermal cycles on Cu-modified Ti64 thin-walled components deposited using the wire-arc directed energy deposition(wire-arc DED)process.For the samples before and after experiencing thermal cycles,it was found that both microstructures consisted of priorβ,grain boundaryα(GBα),and basketweave structures containingα+βlamellae.Thermal cycles realized the refinement ofαlaths,the coarsening of priorβgrains andβlaths,while the size and morphology of continuously distributed GBαremained unchanged.The residualβcontent was increased after thermal cycles.Compared with the heat-treated sample with nanoscale Ti2Cu formed,short residence time in high temperature caused by the rapid cooling rate of thermal cycles restricted Ti2Cu formation.No formation of brittle Ti2Cu means that only grain refinement strengthening and solid-solution strengthening matter.The yield strength increased from 809.9 to 910.85 MPa(12.46%increase).Among them,the main contribution from solid solution strengthening(~51 MPa)was due to the elemental redistribution effect betweenαandβphases caused by thermal cycles through quantitative analysis.The ultimate tensile strength increased from 918.5 to 974.22 MPa(6.1%increase),while fracture elongation increased from 6.78 to 10.66%(57.23%increase).Grain refinement ofαlaths,the promotedα′martensite decomposition,decreased aspect ratio,decreased Schmid factor,and local misorientation change ofαlaths are the main factors in improved ductility.Additionally,although the fracture modes of the samples in the top and middle regions are both brittle-ductile mixed fracture mode,the thermal cycles still contributed to an improvement in tensile ductility.
基金funded by the National Key Research and Development Program of China(Grant No.2023YFC3804205)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX24_2706)the Graduate Innovation Program of China University of Mining and Technology(Grant No.2024WLKXJ203).
文摘Massive fracturing fluid injection in reservoir stimulation can alter the fluid pressure field,potentially inducing the faults to slip in an aseismic or seismic phenomenon.In this work,laboratory friction experiments were performed on split-cutting granite fracture to investigate the effect of fluid pressure on injection-induced slip behavior.The injection experiments spanned a fluid pressure range of 1-20 MPa,which was up to half of the confining pressure.The laboratory results demonstrated that an increase in confining pressure led to a marginal reduction in the friction coefficient,decreasing from a range of 0.70-0.80 at 10 MPa to 0.71-0.75 at 40 MPa.Friction constitutive parameters in experiments with fluid pressure above 10 MPa exhibited a transition from velocity-strengthening to velocity-weakening behavior,while remaining consistently velocity-strengthening below this threshold.Similarly,measurements of dilatancy and critical slip distance exhibited a similar evolution,first increasing and then becoming approximately constant,independent of fluid pressure.The observed microstructural evolution of the split-cutting fractures during slip testing supported these mechanical responses.Post-shear slip,a decrease in the fracture roughness and asperity distribution of the split-cutting fracture was noted,with the decrease in amplitude being more pronounced at high confining pressure.Research may provide a prospect on slip-on faults with fluid pressure.
