Effects of heating rates and alloying elements (Sn, Cu and Cr) on the α → α + β phase transformation of Zr-Sn-Nb-Fe-(Cu, Cr) alloys

In this investigation, differential scanning calorimetry (DSC) and metallographic experiments supplemented by back-scattered electron imaging (BSEI) and electron back-scattered diffraction (EBSD) techniques were performed to study the effects of heating rates and alloying elements on the α → α + β phase transformation of Zr-Sn-Nb-Fe-(Cu, Cr) alloys. Results show that the α → α + β phase transformation peaks shift to higher temperature with increasing heating rates, indicating that the reactions are thermally activated and kinetically controlled processes. The α → α + β phase transformation temperature (Tα→α+β) are affected by the solid solubility limit as well as the diffusivities of various elements in these alloys. For the zirconium alloys with low Nb contents, the Tα→α+β increases with an increase of Sn content. The addition of Cu in zirconium alloys decrease the Tα→α+β, while the addition of Cr increase it.