Abstract
Two complementary compressive creep experiments have been used to investigate potential transformation superplastic effects in polycrystalline ammonium nitrate (NH{sub 4}NO{sub 3}): a micro- deformation apparatus for in-situ observation during deformation under an optical microscope, and a bulk specimen creep apparatus for temperature gradient experiments. Results indicate that more than one experimental effect has been interpreted in the past as transformation superplasticity. We have isolated three effects that produce ``anomalous weakening`` that can be associated with both displacive and reconstructive transformations may operate. These multiple and possibly interdependent mechanisms suggests that transformation superplasticity operates according to a more complex constitutive flow law than has been recognized in the past.
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