Microstructure And Mechanical Properties Of Zr-Cr Alloys

Zirconium(Zr) and Zr alloys were widely used in nuclear industry due to the excellent physical and chemical properties, such as low thermal neutron absorption area and density and good corrosion resistance, oxidation resistance and anti-irradiation. As study going on, researchers found that Zr alloys had a intensively application prospect in the structural materials. Equiaxed microstructure and bimodal structure rendered the alloys with a high strength and good ductility among four typical microstructures of Zr alloys. In this paper, equiaxed microstructure and bimodal structure were obtained by adjusting composition optimization, hot deformation and heat treatments, resulting in increasing the strength and the ductility of Zr-Cr alloys.A series of Zr-Cr alloys were prepared using a vacuum non-consumable electro-arc furnace and the relation of composition, microstructure and mechanical properties was investigated. The results showed that the strength of pure Zr was greatly increased by Cr addition. The strength of the Zr-Cr alloys increased with increasing Cr content,while the ductility of the alloys decreased at the same time. As the Cr content was 1.8 at%, the alloy had the ultimate tensile strength of 1058 MPa and the elongation of 9.6%. When the Cr content is 3 at%, the strength increased and the elongation obviously decreased to 6.2%.The microstructure and the mechanical properties of 1.8Cr alloy with solution and ageing treatment and annealing treatment were investigated. The results showed that the equiaxed microstructure was formed through 900℃ solution treatment, and the ultimate tensile strength and elongation increased to 1109 MPa and 10.9%, respectively. Then the strength decreased and elongation increased with ageing temperature increasing, while the elongation reached a maximum of 18.4% and the strength kept 818 MPa. The Cr content dissolved in solid solution with the Zr sharply decreased, resulting in lattice distortion decreasing, and the strength of 1.8Cr alloy decreased. The strength decreased and elongation increased processed by annealing. There existed a partly recrystallization processed by anneatling at 800℃ and a fully recrystallizaiton at 900℃.