The fundamental mechanism of the cracking formation was investigated for the as-cast GH4151 superalloy.By analyzing the characteristics of cracking,the cracking mechanism was determined to be the cold crack formed dur...The fundamental mechanism of the cracking formation was investigated for the as-cast GH4151 superalloy.By analyzing the characteristics of cracking,the cracking mechanism was determined to be the cold crack formed during the cooling process.And cold cracking is closely related to severe segregation,complex precipitates and uneven γ'phase distribution.During cooling process,cracks were generated around the precipitates due to their different linear shrinkage coefficients.The annealing treatment process controlling the residual stress,the size and morphology of γ'phase was proposed.The annealing treatment plays a role in reducing residual stress through decreasing the thermal gradient and controlling the size distribution of γ'phase to reduce the strain concentration around the precipitate phases.展开更多
The phase precipitation behavior and tensile properties of an as-cast Ni-based alloy,IN617B alloy,after solution heat treatment and long-term aging treatment were investigated.Ti(C,N),M6C and M23C6 are the primary pre...The phase precipitation behavior and tensile properties of an as-cast Ni-based alloy,IN617B alloy,after solution heat treatment and long-term aging treatment were investigated.Ti(C,N),M6C and M23C6 are the primary precipitates in as-cast microstructure.After solution heat treatment,most of carbides dissolve into the matrix except a few fine Ti(C,N)within grains.During long-term aging at 700°C,the phase precipitation behaviors of the alloy are characterized as follows:(1)M23C6 carbides at grain boundaries(GBs)transform from film-like shape to cellular shape and gradually coarsen due to the decrease of the surface energy and element aggregation to GBs;(2)M23C6 carbides within grains have a bar-like morphology with a preferential growth direction[110]and have a cube-on-cube coherent orientation relationship with the matrixγ;(3)γ?particles inhibit the coarsening of M23C6 within grains by constraining the diffusion of formation elements.Furthermore,the tensile strength of the alloy obviously increases,but the ductility significantly decreases after the aging for 5000 h.The alloy has a relatively stable microstructure which guarantees the excellent tensile properties during long-term aging.展开更多
The dislocation structure of directionally solidified(DS)Rene 80 superalloy during tensile and creep deformation has been studied by TEM.In tensile deformation,γ'shearing occurs by slip of APB-coupled(1/2)<110...The dislocation structure of directionally solidified(DS)Rene 80 superalloy during tensile and creep deformation has been studied by TEM.In tensile deformation,γ'shearing occurs by slip of APB-coupled(1/2)<110>dislocation pairs on{111}planes at temperatures below 760℃.and by slip of SISF-seperated(1/3)<112>superpartials which have dissociated on {111}planes into a(1/2)<110>screw superpartial and a(1/6)<112>edge superpartial with an APB in between at temperatures equal to or above 760℃.In creep deformation,γ'shearing occurs again by slip of SISF-seperated(1/3)<112>superpartials which have not dissociated on{111}planes and by diffusive slip of APB-coupled(1/2) <110>dislocation pairs at 760℃,618 MPa.However,no γ'shearing occurs at 980℃,190 MPa.During secondary creep at 760℃,618 MPa or at 980℃,190 MPa,2-dimensional net- works have formed at γ/γ'interfaces,and the strain is mainly the result of diffusion control- led climb of dislocation networks at γ/γ'interfaces.The dependence of secondary creep rate ε upon size a and volume fraction v_■ of cubic γ' has been found to be ■∝α/v_f^(2/3).展开更多
基金Project(50974016)supported by the National Natural Science Foundation of China。
文摘The fundamental mechanism of the cracking formation was investigated for the as-cast GH4151 superalloy.By analyzing the characteristics of cracking,the cracking mechanism was determined to be the cold crack formed during the cooling process.And cold cracking is closely related to severe segregation,complex precipitates and uneven γ'phase distribution.During cooling process,cracks were generated around the precipitates due to their different linear shrinkage coefficients.The annealing treatment process controlling the residual stress,the size and morphology of γ'phase was proposed.The annealing treatment plays a role in reducing residual stress through decreasing the thermal gradient and controlling the size distribution of γ'phase to reduce the strain concentration around the precipitate phases.
基金the financial support from the National Science and Technology Major Project of China (No. J2019-VI-0004-0117)National Natural Science Foundation of China (No. 51905301)。
基金Project(51571191)supported by the National Natural Science Foundation of ChinaProject(NY 20150102)supported by the National Energy Administration Program of China
文摘The phase precipitation behavior and tensile properties of an as-cast Ni-based alloy,IN617B alloy,after solution heat treatment and long-term aging treatment were investigated.Ti(C,N),M6C and M23C6 are the primary precipitates in as-cast microstructure.After solution heat treatment,most of carbides dissolve into the matrix except a few fine Ti(C,N)within grains.During long-term aging at 700°C,the phase precipitation behaviors of the alloy are characterized as follows:(1)M23C6 carbides at grain boundaries(GBs)transform from film-like shape to cellular shape and gradually coarsen due to the decrease of the surface energy and element aggregation to GBs;(2)M23C6 carbides within grains have a bar-like morphology with a preferential growth direction[110]and have a cube-on-cube coherent orientation relationship with the matrixγ;(3)γ?particles inhibit the coarsening of M23C6 within grains by constraining the diffusion of formation elements.Furthermore,the tensile strength of the alloy obviously increases,but the ductility significantly decreases after the aging for 5000 h.The alloy has a relatively stable microstructure which guarantees the excellent tensile properties during long-term aging.
文摘The dislocation structure of directionally solidified(DS)Rene 80 superalloy during tensile and creep deformation has been studied by TEM.In tensile deformation,γ'shearing occurs by slip of APB-coupled(1/2)<110>dislocation pairs on{111}planes at temperatures below 760℃.and by slip of SISF-seperated(1/3)<112>superpartials which have dissociated on {111}planes into a(1/2)<110>screw superpartial and a(1/6)<112>edge superpartial with an APB in between at temperatures equal to or above 760℃.In creep deformation,γ'shearing occurs again by slip of SISF-seperated(1/3)<112>superpartials which have not dissociated on{111}planes and by diffusive slip of APB-coupled(1/2) <110>dislocation pairs at 760℃,618 MPa.However,no γ'shearing occurs at 980℃,190 MPa.During secondary creep at 760℃,618 MPa or at 980℃,190 MPa,2-dimensional net- works have formed at γ/γ'interfaces,and the strain is mainly the result of diffusion control- led climb of dislocation networks at γ/γ'interfaces.The dependence of secondary creep rate ε upon size a and volume fraction v_■ of cubic γ' has been found to be ■∝α/v_f^(2/3).
