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Strain Rate Dependent Environment Assisted Cracking of /-Ti Alloys in Chloride Solution Pages: 24 Published: Jan 2000
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View License Agreement Source: STP1401-EB Abstract Environment assisted cracking (EAC) occurs in annealed-/ Ti-6A1-4V (ELI) and Ti-6Al-2Zr-2Sn-2Cr-2Mo in aqueous chloride solution, as evidenced by rising-displacement threshold stress intensity factors well below K and a mode transition from ductile fracture to transgranular cleavage of . The acicular-/ microstructure of Ti-6-2222 is susceptible to severe cracking in 3.5% NaCl compared to the equiaxed-/ structure of Ti-6-4. Thresholds and growth rates depend on loading rate, and appear most environment sensitive at intermediate crack tip strain rates. EAC is sustained to high loading rates (dK/dt = 0.3 MPam/s for Ti-6-4 and above 10 MPam/s for Ti-6-2222) and crack growth rates are rapid (10 m/s). The hydrogen environment embrittlement mechanism is consistent with such rapid cracking kinetics, but only if the process zone is within 0.001 to 1 m of the crack tip surface. A near-tip process zone may be promoted by high H produced electrochemically on active areas of the crack surface, or by a sharp crack tip.
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