The precipitating regulation and mechanism of TCP phase (μ phase and σ phase) are studied, using electron hole number (EHN) theory, phase analysis technology and TEM observation. The results indicate that the EHN in...The precipitating regulation and mechanism of TCP phase (μ phase and σ phase) are studied, using electron hole number (EHN) theory, phase analysis technology and TEM observation. The results indicate that the EHN in studied alloy is 2.311-2.348 which is higher than that of critical EHN of μ phase precipitate (2.30), so μ phase could precipitate if there is enough thermo-exposition. In contrast, the calculated EHN is less than that of critical EHN of σ phase precipitate (2.52). However the σ phase is also observed by TEM. Enrich of Cr and Mo around γ phase after γ′phase precipitated leads to σ phase precipitated.展开更多
The microstructure of nickel-based single-crystal(SC) superalloys has a pivotal influence on their creep properties. The addition of the Re element not only enhances the long-term creep properties of nickel-based SC s...The microstructure of nickel-based single-crystal(SC) superalloys has a pivotal influence on their creep properties. The addition of the Re element not only enhances the long-term creep properties of nickel-based SC superalloys, but also results in the formation of a topologically close-packed(TCP) phase which is a harmful and brittle hard phase. Here, high-temperature creep interruption tests of a nickel-based SC superalloy that contains4.8 wt% Re were performed under various temperatures and stress conditions, and the evolution of microstructure during creep was observed by scanning electron microscopy(SEM). The volume fraction of the TCP phase was also extracted to explore the mechanism that controls the impacts of the TCP phase on the creep properties.According to the microstructure evolution mechanism, the influence of the TCP phase was attributed to the initial damage and critical shear stress of the material. A creep performance prediction model for nickel-based SC superalloys considering the precipitation of the TCP phase that is based on the crystal plasticity theory and a modified creep damage model was established. The simulation curves fit well with the experimental results and the errors between prediction creep life with test results are within 5%.展开更多
The volume fraction and morphology of the TCP-phase formed in two kinds of Ni-Mo-Cr-Re superalloys under different heat treatment conditions were investigated in this paper. In Re-5% alloy, with increasing of the heat...The volume fraction and morphology of the TCP-phase formed in two kinds of Ni-Mo-Cr-Re superalloys under different heat treatment conditions were investigated in this paper. In Re-5% alloy, with increasing of the heat treatment temperature and prolonging the holding time, the volume fraction of TCP-phase decreased and the TCP-phase size increased. At relatively lower temperature, the TCP-phase prefers to present in the dendrite cores. In Re-10% alloy, the volume fraction and size have the same change tendency as that of in Re-5% alloy, but the morphology will change from needle-like and block-like to sphere when the temperature increases. The TCP-phases formed in these two Ni-Mo-Cr-Re alloys are σ and P phase.展开更多
The application and component designs of single crystal superalloys are restricted by the precipitation of topologically closed packed(TCP)phases,which can deteriorate the microstructural stability of the alloys sever...The application and component designs of single crystal superalloys are restricted by the precipitation of topologically closed packed(TCP)phases,which can deteriorate the microstructural stability of the alloys severely.Limited researches concerning the type and morphology evolution of TCP phases under elevated temperature conditions have been reported previously.In the present work,three Re-containing single crystal alloys were designed to investigate TCP phase evolution via long term isothermal exposure tests at 1120℃while the effects of Re on the microstructural characteristic and elements segregation were also clarified.The results showed that the addition of Re increased the instability of the alloys and the volume fraction of the TCP phases exceeded 5 vol%when the Re content reached 3 wt%.The increasing Re content had also raised the precipitation temperature of TCP phases but it did not change the type of them after long term aging;all the TCP particles were identified asμphase in this study.Moreover,the elements segregation became considerably serious as Re addition increased constantly,which brought about various morphologies of theμphase in the experimental alloys.In particular,the rod-like and needle-likeμphases demonstrated the typical orientation withinγmatrix while the blockyμphase was dispersedly distributed in the space.No specific orientation relationship could be observed in theμphase when the addition of Re exceeded certain threshold value.展开更多
通过对两种成分单晶镍基合金进行蠕变曲线测定,长期时效处理及组织形貌观察,研究了元素W含量对单晶合金组织与性能的影响。结果表明:在N i-A l-Cr-Ta-Co-x%W-5.5%Mo系单晶合金中,4wt%W合金在982℃,200MPa条件下,具有较长的蠕变寿命,随W...通过对两种成分单晶镍基合金进行蠕变曲线测定,长期时效处理及组织形貌观察,研究了元素W含量对单晶合金组织与性能的影响。结果表明:在N i-A l-Cr-Ta-Co-x%W-5.5%Mo系单晶合金中,4wt%W合金在982℃,200MPa条件下,具有较长的蠕变寿命,随W含量增加到6wt%,合金的蠕变寿命明显降低。高W合金在有/无应力时效期间,析出针状μ相,使合金基体出现难溶元素的贫化区,是导致合金蠕变寿命降低的主要原因。其中μ相在(001)晶面沿<110>方向呈相互平行、或垂直的针状形貌析出,沿{111}晶面呈片状方式生长,且与γ′相相邻。展开更多
文摘The precipitating regulation and mechanism of TCP phase (μ phase and σ phase) are studied, using electron hole number (EHN) theory, phase analysis technology and TEM observation. The results indicate that the EHN in studied alloy is 2.311-2.348 which is higher than that of critical EHN of μ phase precipitate (2.30), so μ phase could precipitate if there is enough thermo-exposition. In contrast, the calculated EHN is less than that of critical EHN of σ phase precipitate (2.52). However the σ phase is also observed by TEM. Enrich of Cr and Mo around γ phase after γ′phase precipitated leads to σ phase precipitated.
基金financially supported by the National Natural Science Foundation of China(No.51875462)the Fundamental Research Funds for the Central Universities(No.3102019PY001)+1 种基金the Seed Foundation of Innovation and Creation for Graduate Students in Northwestern Polytechnical University(Nos.ZZ2019015 and ZZ2019017)the National Science and Technology Major Project(Nos.2017-IV-0003-0040 and 2017-V-00030052)。
文摘The microstructure of nickel-based single-crystal(SC) superalloys has a pivotal influence on their creep properties. The addition of the Re element not only enhances the long-term creep properties of nickel-based SC superalloys, but also results in the formation of a topologically close-packed(TCP) phase which is a harmful and brittle hard phase. Here, high-temperature creep interruption tests of a nickel-based SC superalloy that contains4.8 wt% Re were performed under various temperatures and stress conditions, and the evolution of microstructure during creep was observed by scanning electron microscopy(SEM). The volume fraction of the TCP phase was also extracted to explore the mechanism that controls the impacts of the TCP phase on the creep properties.According to the microstructure evolution mechanism, the influence of the TCP phase was attributed to the initial damage and critical shear stress of the material. A creep performance prediction model for nickel-based SC superalloys considering the precipitation of the TCP phase that is based on the crystal plasticity theory and a modified creep damage model was established. The simulation curves fit well with the experimental results and the errors between prediction creep life with test results are within 5%.
基金the financial support from the National High Magnetic Field Laboratory under NSF DMR-0084173
文摘The volume fraction and morphology of the TCP-phase formed in two kinds of Ni-Mo-Cr-Re superalloys under different heat treatment conditions were investigated in this paper. In Re-5% alloy, with increasing of the heat treatment temperature and prolonging the holding time, the volume fraction of TCP-phase decreased and the TCP-phase size increased. At relatively lower temperature, the TCP-phase prefers to present in the dendrite cores. In Re-10% alloy, the volume fraction and size have the same change tendency as that of in Re-5% alloy, but the morphology will change from needle-like and block-like to sphere when the temperature increases. The TCP-phases formed in these two Ni-Mo-Cr-Re alloys are σ and P phase.
基金financially supported by the State Key Lab of Advanced Metals and Materials Open Fund under Grant No.2018-Z07the National Science and Technology Major Project under Grant No.2017-VI-0002-0072+2 种基金the National Key R&D Program of China under Grant No.2017YFA0700704the National Natural Science Foundation of China(NSFC)under Grant Nos.51601192,51671188the Youth Innovation Promotion Association,Chinese Academy of Sciences
文摘The application and component designs of single crystal superalloys are restricted by the precipitation of topologically closed packed(TCP)phases,which can deteriorate the microstructural stability of the alloys severely.Limited researches concerning the type and morphology evolution of TCP phases under elevated temperature conditions have been reported previously.In the present work,three Re-containing single crystal alloys were designed to investigate TCP phase evolution via long term isothermal exposure tests at 1120℃while the effects of Re on the microstructural characteristic and elements segregation were also clarified.The results showed that the addition of Re increased the instability of the alloys and the volume fraction of the TCP phases exceeded 5 vol%when the Re content reached 3 wt%.The increasing Re content had also raised the precipitation temperature of TCP phases but it did not change the type of them after long term aging;all the TCP particles were identified asμphase in this study.Moreover,the elements segregation became considerably serious as Re addition increased constantly,which brought about various morphologies of theμphase in the experimental alloys.In particular,the rod-like and needle-likeμphases demonstrated the typical orientation withinγmatrix while the blockyμphase was dispersedly distributed in the space.No specific orientation relationship could be observed in theμphase when the addition of Re exceeded certain threshold value.
文摘通过对两种成分单晶镍基合金进行蠕变曲线测定,长期时效处理及组织形貌观察,研究了元素W含量对单晶合金组织与性能的影响。结果表明:在N i-A l-Cr-Ta-Co-x%W-5.5%Mo系单晶合金中,4wt%W合金在982℃,200MPa条件下,具有较长的蠕变寿命,随W含量增加到6wt%,合金的蠕变寿命明显降低。高W合金在有/无应力时效期间,析出针状μ相,使合金基体出现难溶元素的贫化区,是导致合金蠕变寿命降低的主要原因。其中μ相在(001)晶面沿<110>方向呈相互平行、或垂直的针状形貌析出,沿{111}晶面呈片状方式生长,且与γ′相相邻。
