Effect of Heat Treatment on Tensile Properties and Microstructure of New Domestic Zirconium Alloys

The tensile properties of stress relieved（SR） and recrystallized（RX） alloys, with two different compositions, namely SZA4（Zr-0.8 Sn-0.25 Nb-0.35 Fe-0.1 Cr-0.05 Ge） and SZA6（Zr-0.5 Sn-0.5 Nb-0.3 Fe-0.015 Si） at room temperature（RT） and 385 ℃were studied by MTS material test machine, the fracture morphology of alloys was observed by scanning electron microscopy（SEM） and the microstructure was observed by transmission electronic microscopy（TEM）. The results showed that each alloy was excellent on mechanical properties, SZA4-450℃was the strongest while SZA4-560℃ and SZA6-560℃ had the best elongation.The fracture mode of alloys was ductile, according with lots of dimples in the fracture morphology, second phase particles（SPPs） which were also observed by SEM, distributing in the base uniformly and dispersely. There were two kinds of SPPs which were observed by TEM in SZA-4 alloy, one was Zr（Nb Fe Cr）2 with a smaller size and the other was Zr（Nb Fe Cr Ge）2 with a larger size, both of them had a HCP structure. In SZA-6,（Zr Nb）2 Fe SPPs with a FCC structure and Zr（Nb Fe）2 SPPs with a HCP structure was found. The effect of heat treatment and composition on alloys was analyzed, showing that the heat treatment played a dominant role.