Novel high-strength ternary Zr–Al–Sn alloys with martensite structure for nuclear applications

High strength is essential for the practical application of Zr alloys as structural materials. In this work, Zr–5Al–xSn (x = 2, 3, 4, 5 and 6) alloys have been designed and fabricated through arc melting in order to effectively improve the strength while retaining good ductility. Phase analysis results show that all the samples consist of single phase α-Zr. The variation trend of lattice constants as a function of Sn content has been analyzed. The microstructural analysis indicates that the Zr–5Al–xSn alloys mainly contain martensite structure. Mechanical tests show that these Zr–5Al–xSn alloys exhibit high compressive strength (1250–1450 MPa), high yield stress (800–1000 MPa), and favorable plastic strain of 18–23%. The fracture mode has been experimentally analyzed. Finally, both Zr–5Al–3Sn and Zr–5Al–5Sn are subjected to heat treatments for further study on the roles of Sn element and controlled heat treatment on the microstructure and mechanical properties of Zr alloys. Sn is found to promote the formation of ZrAl in the Zr–5Al–xSn alloys. Moreover, the martensite laths are observed to evolve into larger strip grains and fine equiaxed grains after heat treatment at 900 °C for 2 h. These factors strengthen the Zr–5Al–xSn alloys.