Abstract and subjects
Zirconium transforms from the alpha+omega phase under high hydrostatic pressures. The critical transformation pressure is expected to be affected by internal stresses associated with defects. This study focuses on the effects of dis-locations and twins and their associated stress fields on the transformation. Samples are pre-loaded to seed dislocations or twins. In-situ high-hydrostatic-pressure X-ray synchrotron experiments are performed revealing that microstructures with pre-existing prismatic (a) dislocations and {101 over bar 2} twins promote the transformation more effectively than pyramidal (c + a) dislocations or {112 over bar 2} twins. Post-mortem electron backscatter diffraction further shows that pre-seeded defects stabilize the omega-phase at ambient conditions. In-situ stress-hold neutron diffraction experiments are also performed combining both hydrostatic and deviatoric stresses capturing the role of deviatoric stresses on phase transformation kinetics. These results support the findings of recent atomistic simulations indicating flow of prismatic (a) dislocations at an alpha-omega interface promotes the growth of the omega domain.