多轴锻造与T852热处理对Al-Cu-Li合金组织及力学性能的影响

Effects of multi-axial forging and T852 heat treatment on microstructure and mechanical properties of Al-Cu-Li alloy

采用SEM、EBSD、TEM和拉伸试验等方法,研究不同道次多轴锻造及T852热处理对Al-Cu-Li合金显微组织和力学性能的影响。结果表明,Al-Cu-Li合金经多道次多轴锻造后晶粒被显著细化,晶粒尺寸由均匀化退火态的450μm减小至6道次的5μm,晶粒细化机制以连续动态再结晶为主,且伴随不连续动态再结晶;6道次锻造合金经T852热处理后,晶界析出相呈不连续分布,晶内析出大量板条状T_(1)相及少量θ′相,与均匀化退火态粗化T_(1)相相比,时效析出T_(1)相发生了明显细化;6道次锻造且T852热处理后,合金的抗拉强度、屈服强度及伸长率分别高达544 MPa、462 MPa和8.6%,依次为均匀化退火态的2.0、2.4及4.1倍,而且相应的断裂模式由脆性断裂转变为韧性断裂。

Effect of multi-axial forging with different passes and T852 heat treatment on microstructure and mechanical properties of Al-Cu-Li alloy was studied by means of SEM,EBSD,TEM and tensile test.The results show that the grain structure of the Al-Cu-Li alloy is significantly refined after multi-pass multi-axial forging,and the grain size is reduced from 450μm in as-homogenized state to 5μm in as-forged state with six passes.The grain refinement mechanism is mainly continuous dynamic recrystallization,accompanied by discontinuous dynamic recrystallization.After T852 heat treatment,the precipitates on grain boundary of the as-forged alloy with six passes present discontinuous distribution,and a large number of lath-shaped T_(1) phases and a small amount ofθ′phases are precipitated in the grains.Compared with the coarsened T_(1) phase in as-homogenized state,the T_(1) phase in as-aged state is obviously refined.After 6 passes forging and T852 heat treatment,the tensile strength,yield strength and elongation of the alloy are 544 MPa,462 MPa and 8.6%,respectively,which are 2.0,2.4 and 4.1 times of those in as-homogenized state,and the corresponding fracture mode changes from brittle fracture to ductile fracture.