Characterization of Titanium Alloys Produced by Electron Beam Directed Energy Deposition

Newman, John A ; Tayon, Wesley A ; Ruggles, Timothy J ; Yeratapally, Saikumar R ; Brice, Craig A ; Hochhalter, Jacob D ; Baughman, James M ; Claytor, Harold D

关键词: TITANIUM ALLOYS;    ELECTRON BEAMS;    ENERGY TRANSFER;    ADDITIVE MANUFACTURING;    CRACK PROPAGATION;    MICROSTRUCTURE;    CRYSTAL STRUCTURE;    TENSILE PROPERTIES;    GRAIN BOUNDARIES;    DISLOCATIONS (MATERIALS);   

RP-ID  :  NASA/TM-2018-220111,L-20975,NF1676L-31702

学科分类：金属与冶金

美国|英语

来源: NASA Technical Reports Server

【 摘 要 】

Functionally graded materials offer the potential to improve structural efficiency by allowing the material composition and/or microstructural features to spatially vary within a component. Additive manufacturing techniques enable the fabrication of such graded materials and structures. While examining several titanium alloys, this paper focuses on Ti-8Al-1Er as it has a unique microstructure that is only feasible when produced by rapid solidification methods like electron beam directed energy deposition, an additive manufacturing process. The results show that, when mixed, Ti-8Al-1Er and commercially-pure titanium uniformly mix at various ratios and the resultant static tensile properties of the mixed alloys behave according to rule-of-mixtures. At discontinuous interfaces between Ti-8Al-1Er and commercially-pure titanium, the crack growth behavior progresses smoothly across the discontinuity as the crack transitions from one crack growth regime into another. Studies on monolithic samples shows the mechanisms of damage in the Ti-8Al-1Er; specifically, that strain localization occurs near grain boundaries of high mis-orientation on the microscale and that twinning and dislocation density is concentrated near erbia-strengthening particles (Er2O3) on the nanoscale.