Size effect of mechanical properties and fracture behavior of TA1 foil
Uniaxial tensile experiments were carried out on TA1 foils with thickness of 100 μm and different grain sizes to study the size effects of mechanical properties and fracture behavior,and the micro-scale constitutive equation based on the size effects was constructed.The results show that the tensile stress and strength of titanium foil increase with the increase of grain size,and the elongation decreases slowly to 25％at first,and then decreases rapidly.During tensile process,the necking stage and the gentle stage shorten continuously.Except for the sample with grain size of 56.88 μm,the fracture angle of the other samples is 50°-60°,which is typical shear fracture.When the grain size exceeds 21.08 μm,the number of tear edges and dimple on the fracture surface decreases continuously,and the frac-ture mode changes from plastic fracture to quasi-cleavage fracture.When the grain size exceeds 36.14 μm,the titanium foil matrix chan-ges from HCP-Ti structure to FCC-Ti structure,and the dislocation density decreases,and obvious cleavage fracture characteristics appear on the fracture surface.The fracture mode completely changes to cleavage fracture.Based on the surface layer model,the constitutive model considering the size effect can accurately predict the mechanical properties of micro-scale titanium foil during tensile process.
size effectTA1 foilmechanical propertyfracture behaviorconstitutive model
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