Low cycle fatigue (LCF)tests under different total strain amplitudes have been conducted in order to ascertain the effect of precipitate sizes on LCF behavior of 8090 Al-Li alloy. A constant strain rate of 3×10-3...Low cycle fatigue (LCF)tests under different total strain amplitudes have been conducted in order to ascertain the effect of precipitate sizes on LCF behavior of 8090 Al-Li alloy. A constant strain rate of 3×10-3s-1 and symmetrical triangular waveform were employed for all tests. It is found that the cyclic stress response of the alloy varied with the precipitate sizes and strain amplitudes. The materials in all conditions cyclically handen at first and the higher the strain amplitude, the greater the amount of hardening. The low cyclic flow stress is the highest in the peakaged condition. TEM and SEM observations demonstrated that cyclic stress-strain behavior and fracture mode of Al-Li alloy are closely related to an increase in the dislocation density and interaction between the precipitates and dislocations, sizes of δ particles and pricipitate free zone (PFZ) at grain boundaries.展开更多
The creep and fracture behavior of the cast K417 and forged GH4049 nickel-based superalloys were investigated in the temperature range of 700-900℃ C. Within the ranges of stress and temperature studied, the steady st...The creep and fracture behavior of the cast K417 and forged GH4049 nickel-based superalloys were investigated in the temperature range of 700-900℃ C. Within the ranges of stress and temperature studied, the steady state creep rates exhibited a power law relationship with the applied stress and temperature. The time to rupture is inversely proportional to the steady state creep rate. Under all testing conditions, the creep fracture process was mainly controled by crack initiation and growth of the intergranular oxidation. Casting porosities, pores and carbides were also prefecentral locations of creep crack initiation in the cast K417 alloy. In addition, the intergranular fracture feature in the forged GH4049 alloy was apparently associated with the formation and coalescence of the cavitations on the grain boundaries.展开更多
文摘Low cycle fatigue (LCF)tests under different total strain amplitudes have been conducted in order to ascertain the effect of precipitate sizes on LCF behavior of 8090 Al-Li alloy. A constant strain rate of 3×10-3s-1 and symmetrical triangular waveform were employed for all tests. It is found that the cyclic stress response of the alloy varied with the precipitate sizes and strain amplitudes. The materials in all conditions cyclically handen at first and the higher the strain amplitude, the greater the amount of hardening. The low cyclic flow stress is the highest in the peakaged condition. TEM and SEM observations demonstrated that cyclic stress-strain behavior and fracture mode of Al-Li alloy are closely related to an increase in the dislocation density and interaction between the precipitates and dislocations, sizes of δ particles and pricipitate free zone (PFZ) at grain boundaries.
文摘The creep and fracture behavior of the cast K417 and forged GH4049 nickel-based superalloys were investigated in the temperature range of 700-900℃ C. Within the ranges of stress and temperature studied, the steady state creep rates exhibited a power law relationship with the applied stress and temperature. The time to rupture is inversely proportional to the steady state creep rate. Under all testing conditions, the creep fracture process was mainly controled by crack initiation and growth of the intergranular oxidation. Casting porosities, pores and carbides were also prefecentral locations of creep crack initiation in the cast K417 alloy. In addition, the intergranular fracture feature in the forged GH4049 alloy was apparently associated with the formation and coalescence of the cavitations on the grain boundaries.
