采用透射电镜(TEM)和扫描电镜(SEM)分析了不同时效热处理制度下镍基GH99高温合金中γ'相的尺寸、形貌变化,采用维氏硬度计测试不同时效热处理制度下的合金硬度。结果表明:γ'相随着时效温度的升高和保温时间的延长而明显粗化,...采用透射电镜(TEM)和扫描电镜(SEM)分析了不同时效热处理制度下镍基GH99高温合金中γ'相的尺寸、形貌变化,采用维氏硬度计测试不同时效热处理制度下的合金硬度。结果表明:γ'相随着时效温度的升高和保温时间的延长而明显粗化,其粗化符合沉淀相粗化理论(LSW理论);随着γ'相的不断长大,部分γ'相的形貌由球形转变为立方形。经计算得到γ'相长大激活能约为248.8 k J/mol。此外发现硬度随γ'相尺寸的增大而逐渐增大,但当γ'相尺寸超过37.2 nm时,硬度随γ'相长大呈下降趋势,在750℃时得到合金的最大硬度为395.16 HV。展开更多
A novel graphene reinforced BNi-2 composite filler was developed for brazing GH99 superalloy. The interracial microstructure of brazed joints was analyzed by field emission scanning electron microscope and a transmiss...A novel graphene reinforced BNi-2 composite filler was developed for brazing GH99 superalloy. The interracial microstructure of brazed joints was analyzed by field emission scanning electron microscope and a transmission electron microscope. The effects of graphene addition on the microstructure evolu-tion and mechanical properties of brazed joints were investigated, and the strengthening mechanism of graphene was analyzed. The results revealed that due to the addition of graphene, M23（C,B）6 compounds were synthesized in the y solid solution and brittle boride precipitates near the brazing seam decreased. Graphene was effective in retarding solute atoms diffusion thus impeding the precipitation of borides. Furthermore, the low coefficient of thermal expansion （CTE） of graphene was conducive to relieve stress concentration of the brazed joints during the cooling process. The shear strengths of brazed joints were significantly improved by exerting the strengthening effect of graphene. The maximum shear strengths of the brazed joints were 410.4 MPa and 329.7 MPa at room temperature and 800 ℃, respectively.展开更多
Superalloy thin-walled structures are achieved mainly by brazing,but the deformation process of brazed joints is non-uniform,making it a challenging research task.This paper records a thorough investigation of the eff...Superalloy thin-walled structures are achieved mainly by brazing,but the deformation process of brazed joints is non-uniform,making it a challenging research task.This paper records a thorough investigation of the effect of brazing parameters on the microstructure of joints and its mechanical properties,which mainly inquires into the deformation and fracture mechanisms in the shearing process of GH99/BNi-5a/GH99 joints.The macroscopic-microscopic deformation mechanism of the brazing interface during shearing was studied by Crystal Plasticity(CP)and Molecular Dynamics(MD)on the basis of the optimal brazing parameters.The experimental results show that the brazing interface is mainly formed by(Ni,Cr,Co)(s,s)and possesses a shear strength of approximately 546 MPa.The shearing fracture of the brazed joint occurs along the brazing seam,displaying the characteristics of intergranular fracture.MD simulations show that dislocations disassociate and transform into fine twinning with increased strain.CP simulated the shear deformation process of the brazed joint.The multiscale simulation results are consistent with the experimental results.The mechanical properties of thin-walled materials for brazing are predicted using MD and CP methods.展开更多
The dissimilar brazing of Nb521 niobium alloy to GH99 superalloy was achieved successfully using Ti–35Ni brazing filler under vacuum.The effects of brazing temperature and holding time were systematically analyzed on...The dissimilar brazing of Nb521 niobium alloy to GH99 superalloy was achieved successfully using Ti–35Ni brazing filler under vacuum.The effects of brazing temperature and holding time were systematically analyzed on the interfacial microstructure evolution and mechanical properties of joints.The joints brazed at 1120℃ for 10 min exhibited a typical interfacial structure composed of Nb521/β-(Nb,Ti)+TiNi/TiNi+Ti_(2)Ni/TiNi+TiNi_(3)/Cr-rich TiNi/Ti-rich(Ni,Cr)_(ss)/(Ni,Cr)_(ss)/GH99.The findings indicated that as the brazing temperature or holding time increased,the presence of brittle Ti_(2)Ni compounds decreased while the formation of TiNi_(3) gradually increased and tended to coarsen.The shear strength of joints exhibited variations corresponding to changes in interfacial brittle compound,and reached the highest value of 121 MPa at 1120℃ for 10 min.In the context of shear testing,all joints displayed clear brittle fracture patterns,with fractures predominantly occurring at the brittle compounds,namely,Ti_(2)Ni and TiNi_(3) phases.展开更多
文摘采用透射电镜(TEM)和扫描电镜(SEM)分析了不同时效热处理制度下镍基GH99高温合金中γ'相的尺寸、形貌变化,采用维氏硬度计测试不同时效热处理制度下的合金硬度。结果表明:γ'相随着时效温度的升高和保温时间的延长而明显粗化,其粗化符合沉淀相粗化理论(LSW理论);随着γ'相的不断长大,部分γ'相的形貌由球形转变为立方形。经计算得到γ'相长大激活能约为248.8 k J/mol。此外发现硬度随γ'相尺寸的增大而逐渐增大,但当γ'相尺寸超过37.2 nm时,硬度随γ'相长大呈下降趋势,在750℃时得到合金的最大硬度为395.16 HV。
基金supported financially by the National Natural Science Foundation of China(Nos.51505105,51775138 and U1537206)the International Science&Technology Cooperation Program of China(No.2015DFA50470)the Key Research&Development program of Shandong Province(No.2017GGX40103)
文摘A novel graphene reinforced BNi-2 composite filler was developed for brazing GH99 superalloy. The interracial microstructure of brazed joints was analyzed by field emission scanning electron microscope and a transmission electron microscope. The effects of graphene addition on the microstructure evolu-tion and mechanical properties of brazed joints were investigated, and the strengthening mechanism of graphene was analyzed. The results revealed that due to the addition of graphene, M23（C,B）6 compounds were synthesized in the y solid solution and brittle boride precipitates near the brazing seam decreased. Graphene was effective in retarding solute atoms diffusion thus impeding the precipitation of borides. Furthermore, the low coefficient of thermal expansion （CTE） of graphene was conducive to relieve stress concentration of the brazed joints during the cooling process. The shear strengths of brazed joints were significantly improved by exerting the strengthening effect of graphene. The maximum shear strengths of the brazed joints were 410.4 MPa and 329.7 MPa at room temperature and 800 ℃, respectively.
基金support from the National Natural Science Foundation of China(Grant Nos.52175307)the Taishan Scholars Foundation of Shandong Province(No.tsqn201812128)+1 种基金the Natural Science Foundation of Shandong Province(No.ZR2023JQ021No.ZR2020QE175).
文摘Superalloy thin-walled structures are achieved mainly by brazing,but the deformation process of brazed joints is non-uniform,making it a challenging research task.This paper records a thorough investigation of the effect of brazing parameters on the microstructure of joints and its mechanical properties,which mainly inquires into the deformation and fracture mechanisms in the shearing process of GH99/BNi-5a/GH99 joints.The macroscopic-microscopic deformation mechanism of the brazing interface during shearing was studied by Crystal Plasticity(CP)and Molecular Dynamics(MD)on the basis of the optimal brazing parameters.The experimental results show that the brazing interface is mainly formed by(Ni,Cr,Co)(s,s)and possesses a shear strength of approximately 546 MPa.The shearing fracture of the brazed joint occurs along the brazing seam,displaying the characteristics of intergranular fracture.MD simulations show that dislocations disassociate and transform into fine twinning with increased strain.CP simulated the shear deformation process of the brazed joint.The multiscale simulation results are consistent with the experimental results.The mechanical properties of thin-walled materials for brazing are predicted using MD and CP methods.
基金the National Natural Science Foundation of China(Grant No.52175307)Shandong Natural Science Foundation(Grant No.ZR2023JQ021).
文摘The dissimilar brazing of Nb521 niobium alloy to GH99 superalloy was achieved successfully using Ti–35Ni brazing filler under vacuum.The effects of brazing temperature and holding time were systematically analyzed on the interfacial microstructure evolution and mechanical properties of joints.The joints brazed at 1120℃ for 10 min exhibited a typical interfacial structure composed of Nb521/β-(Nb,Ti)+TiNi/TiNi+Ti_(2)Ni/TiNi+TiNi_(3)/Cr-rich TiNi/Ti-rich(Ni,Cr)_(ss)/(Ni,Cr)_(ss)/GH99.The findings indicated that as the brazing temperature or holding time increased,the presence of brittle Ti_(2)Ni compounds decreased while the formation of TiNi_(3) gradually increased and tended to coarsen.The shear strength of joints exhibited variations corresponding to changes in interfacial brittle compound,and reached the highest value of 121 MPa at 1120℃ for 10 min.In the context of shear testing,all joints displayed clear brittle fracture patterns,with fractures predominantly occurring at the brittle compounds,namely,Ti_(2)Ni and TiNi_(3) phases.
