Damage evolution behavior and damage constitutive model of selective-laser-melted Ti6Al4V alloy under different heat treatment temperatures

ABSTRACT

To study the damage evolution behavior and damage constitutive model of selective-laser-melted (SLMed) Ti6Al4V alloy under different heat treatment temperatures, tensile tests were conducted. The effect of heat treatment temperature on microstructure and mechanical properties of SLMed Ti6Al4V alloy is discussed. Elastic modulus was selected to characterize damage, and the damage evolution law of SLMed Ti6Al4V alloy was quantitatively analyzed, establishing the damage evolution equation. Based on the theory of continuous damage mechanics, the Ramberg-Osgood model was introduced to establish the damage constitutive model of SLMed Ti6Al4V alloy under different heat treatment temperatures. The results show that with increasing heat treatment temperature, the acicular α′ phase in the microstructure of SLMed Ti6Al4V alloy is gradually transformed into α + β phase, the α phase is gradually coarsened, the volume fraction of β phase gradually increased. The microhardness and tensile strength of the SLMed Ti6Al4V alloy decreased from 376.44 HV and 1171.5 MPa to 317.31 HV and 790.9 MPa, while elongation increased from 6.6% to 13.6% and then decreased to 11.1%. The critical strain in the as-deposited sample is 0.009, entering the rapid damage accumulation stage first, whereas heat-treated samples lag significantly. The error between model and experimental results is within 7%.

Keywords:
Heat treatment; Selective-laser-melted Ti6Al4V alloy; Damage evolution; Damage constitutive model