Hydrogen-induced transformation superplasticity in zirconium

Commercially-pure zirconium is alloyed and dealloyed repeatedly with hydrogen at 810 °C, thereby cyclically triggering phase transformations between hydrogen-free α-Zr and hydrogen-alloyed β-Zr. Under an externally applied tensile stress, the internal mismatch stresses produced by the α-β transformations are biased, resulting in the accumulation of strain increments after each chemical cycle in the direction of the applied stress. Two key parameters, i.e., half-cycle time and applied stress, are examined to determine their effects on the strain increments. A tensile strain of 133% is achieved without fracture after multiple chemical cycles, demonstrating for the first time transformation superplasticity in zirconium induced by isothermal hydrogen cycling.