The pre-compressed CT technique was used to quantitatively investigate the formation of stress relaxation cracks under different tensile residual stresses and aging time in Super304H austenitic stainless steel weld me...The pre-compressed CT technique was used to quantitatively investigate the formation of stress relaxation cracks under different tensile residual stresses and aging time in Super304H austenitic stainless steel weld metal.The statistical results revealed that intergranular cracks could occur within 2000 h under 650℃ when the residual stress was applied with greater than 18 KN pre-compression force.Detailed grain interior and boundary analyses showed that the growth of intragranular Cu-rich particles could induce a strong grain interior,and the intergranular Nb(C,N)carbides were one of the causes to crack under short-term aging time.For long-term aging time conditions,the intergranular M_(23)C_(6)carbides were more susceptible to crack than intergranular Nb(C,N)carbides.Finally,the mechanism responsible for stress relaxation cracking formation was carefully illustrated for the weld metals after short-term aging and long-term aging,respectively.展开更多
Creep behavior of Super304H austenitic steel has been investigated at elevated temperatures of 923-973 K and at applied stress of 190-210 MPa. The results show that the apparent stress exponent and activation energy i...Creep behavior of Super304H austenitic steel has been investigated at elevated temperatures of 923-973 K and at applied stress of 190-210 MPa. The results show that the apparent stress exponent and activation energy in the creep deformation range from 16.2 to 27.4 and from 602.1 to 769.3 kJ/mol at different temperatures, respectively. These high values imply the presence of a threshold stress due to an interaction between the dislocations and Cu-rich precipitates during creep deformation. The creep mechanism is associated with the dislocation climbing governed by the matrix lattice diffusion. The origin of the threshold stress is mainly attributed to the coherency strain induced in the matrix by Cu-rich precipitates. The theoretically estimated threshold stresses from Cu-rich precipitates agree reasonably with the experi- mental results.展开更多
基金supported by the Shenyang National Laboratory for Materials Science Innovation Projects L2019R35。
文摘The pre-compressed CT technique was used to quantitatively investigate the formation of stress relaxation cracks under different tensile residual stresses and aging time in Super304H austenitic stainless steel weld metal.The statistical results revealed that intergranular cracks could occur within 2000 h under 650℃ when the residual stress was applied with greater than 18 KN pre-compression force.Detailed grain interior and boundary analyses showed that the growth of intragranular Cu-rich particles could induce a strong grain interior,and the intergranular Nb(C,N)carbides were one of the causes to crack under short-term aging time.For long-term aging time conditions,the intergranular M_(23)C_(6)carbides were more susceptible to crack than intergranular Nb(C,N)carbides.Finally,the mechanism responsible for stress relaxation cracking formation was carefully illustrated for the weld metals after short-term aging and long-term aging,respectively.
基金financially supported by the National Natural Science Foundation of China(No.50931003)the Shanghai Science and Technology Committee(No.13dz2260300)
文摘Creep behavior of Super304H austenitic steel has been investigated at elevated temperatures of 923-973 K and at applied stress of 190-210 MPa. The results show that the apparent stress exponent and activation energy in the creep deformation range from 16.2 to 27.4 and from 602.1 to 769.3 kJ/mol at different temperatures, respectively. These high values imply the presence of a threshold stress due to an interaction between the dislocations and Cu-rich precipitates during creep deformation. The creep mechanism is associated with the dislocation climbing governed by the matrix lattice diffusion. The origin of the threshold stress is mainly attributed to the coherency strain induced in the matrix by Cu-rich precipitates. The theoretically estimated threshold stresses from Cu-rich precipitates agree reasonably with the experi- mental results.
