Grain Equilization In Zirconium-aluminum Binary Alloys

Zirconium and zirconium alloys are used in nuclear industry and chemical industrydue to the excellent physic-chemical properties, such as good anti-irradiation, corrosionresistance, oxidation resistance, small thermal expansion coefficient, low density andsmall neutron absorption area. With the in-depth study, researchers have found thatzirconium alloys have excellent mechanical properties and are used in aerospace fieldgradually. However, zirconium alloys have low plasticity, which makes their applicationbe restricted. In this case, it is vital to find a method to improve the plasticity whilekeeping the high strength. In this paper, we select the Zr-Al binary alloy as the modelmaterial to make the grains or microstructure equiaxed by the methods such ascomposition adjustment, deformation and heat treatment, in order to improve the plasticityultimately.A series of alloys with different contents of aluminum were designed and ingots wereprepared by non-consumable arc melting furnace. Experimental results show the alloys’microstructure was mainly α phase when the content of aluminum is lower than12at%. Asthe content of aluminum increases, intermetallic compounds would appear in themicrostructure. Rolling of the alloys was then applied in the the two-phase region, and themicrostructure and properties were investigated, in which recrystallization occured withmany short bar-shaped grains in the samples. Accordingly, the properties of the alloyswere increased.After investigation of optimization of composition and property, two kinds of alloyswith different aluminum contents (9at%and12at%) were selected for further study ofgrain refinement and equalization, mainly by changing the temperature of rolling and thetemperatures of afterward heat treatments. The results showed that recrystallizationoccurred in the microstructure of samples. Aparrently the grains were nodularized.Because of the equi-axed grains, the elongation rate of the samples was significantlyimproved. By further optimizing experimental parameters, fine and equ-axialrecrystallized grains can be obtained for the alloys with9at%and12at%aluminum after rolling at870℃followed by water quenched, for which the mechanical properties werealso optimized.