铸造Be-37.6Al-0.4Sc合金的力学性能及断裂行为研究

Mechanical Properties and Fracture Behaviors of Cast Be-37.6Al-0.4Sc Alloy

采用纳米压痕和拉伸试验对铸造Be-37.6Al-0.4Sc合金的力学性能进行表征,结合微观组织及断口形貌,分析研究Sc合金化对铸造铍铝合金组织性能和断裂行为的影响。结果发现,Sc合金化使粗大的铍柱状树枝晶转变为尺寸均匀细小的等轴晶,提高合金强度但降低了塑性。含Sc第二相具有最大的弹性模量,为321.48 MPa,硬度为9.83GPa,最小塑性指数为0.803。铍/铝相界面处的第二相不是基体相的裂纹源,铍晶粒内多面形第二相诱发铍晶粒微裂纹的形成。合金拉伸断裂方式表现为铍相脆性解理断裂和铝相延性韧窝断裂的混合断裂模式。

The mechanical properties of cast Be-37.6Al-0.4Sc alloy were characterized by nano-indentation and tensile tests,and effects of Sc-alloying on the microstructure and fracture behaviors of the alloy were investigated via tensile fractography and optical metallography.With Sc alloying,the microstructure of the Be-Al alloy is converted from coarse columnar dendritics to uniform and fine equiaxed grain,which are responsible for improving strength and decreasing plasticity.The Sc-containing secondary phases presents the highest elastic modulus of 321.48 MPa,the highest hardness of 9.83 GPa and the lowest plasticity index of 0.803 compared with those of the matrix alloy.The secondary phases locating at the Be/Al interfaces is not acted as pre-existing micro-crack sources during the deformation,whereas the highly-faceted secondary phases within Be grains induced the formation of micro-cracks and resulted in the decrease of elongation.The failure mode of Be-37.6Al-0.4Sc alloy are characterized by brittle cleavage failure of Be regions and ductile dimple failure of Al regions compared with the Be-Al alloy.