Effect Of Microstructure On Creep Crack Growth Behavior Of 2219 Aluminum Alloy

2219 aluminum alloy has a wide range of applications in the field of aerospace.As a representative of heat-resistant aluminum alloy,the research on its high temperature fracture performance is rarely reported.In this paper,the effects of load and grain size on the creep crack propagation performance of 2219 aluminum alloy were investigated by means of experimental analysis.Firstly,in order to observe the variation of grain size and microhardness with annealing temperature,the 2219 aluminum alloy in the solid solution state were cold rolled to 50% and 75% deformation amount and then recrystallization annealing at between 400-540 degree Celsius was performed.Results indicated that,the average grain size of experimental materials with different deformation amount decreased first and then increased with the solid solution temperature increasing when kept for 1h.The minimum grain size was obtained at 480 degree Celsius,and the complete equiaxed grains were obtained at 520 degree Celsius.Under the same recrystallization annealing condition,the more deformation amount was,the smaller and more uniform grain can be got.Microhardness increased with the increasing recrystallization annealing temperature.The average equiaxed grain size of experimental material after cold rolled to 50% deformation amount and then annealed at 540 degree Celsius for 1h was 33.20?m,and the average equiaxed grain size of experimental material after cold rolled to 75% deformation amount and then annealed at 520 degree Celsius for 1h was 19.39?m.Secondly,in order to study the variation of second phase and grain size with aging time,the above two kinds of materials with equiaxial grains were selected as experimental materials for aging at 310 degree Celsius at different time.Results showed that the microstructures of both group experimental materials reached a steady state after aged for 16 h and the grain size didn't change throughout the aging process.What's more,the creep crack growth(CCG)experiments of aged material with equiaxial grains under different load and at 300 degree Celsius were carried out to study the effect of load on material's CCG performance.Results showed that CCG rate increases with increasing load.It can be seen from the relationship curve of CCG rate with different fracture mechanic parameters such as stress intensity factor ,net section stressnet? and modified J-integral(9)C that there is significant correlationship between and CCG rate.At last,in order to study the effect of microstructure on the CCG property of the material,the CCG experiments of materials with different microstructure under the same conditions show that the smaller grain size was,the weaker creep crack growth resistance material performed.Creep fracture morphology analysis showed that the fracture mode changed gradually from intergranular brittle fracture to transgranular ductile fracture with creep crack length and growth rate increaseing.