Design Of Zr-Nb Alloys With Low Modulus And High Strength Based On Spinodal Decomposition And Optimization Of Their Microstructures And Mechanical Properties

Zirconium and zirconium alloys have excellent properties such as lower elastic modulus,higher specific strength,excellent biocompatibility,better bioadhesion,excellent corrosion resistance,and lower magnetization coefficient,which have promising applications in the field of biomedical materials such as human tissue and organ repair and replacement.Usually,the strengthening methods of β-bioalloys with body-centered cubic structure mainly include precipitation strengthening or finegrained strengthening,but these methods will lead to an increase in elastic modulus while improving the strength of the alloy.In contrast,spinodal decomposition has the advantages of fine and uniform precipitated phase organization,identical crystal structure and co-grid,which can substantially increase the strength of the alloy without increasing the elastic modulus.The existence of large miscibility gaps in the phase diagram of Zr-Nb binary alloys has been studied,which provides guidance for the design of Zr-Nb alloys with amplitude modulation.Therefore,in this paper,several high-strength and low-mode Zr-Nb alloys with spinodal decomposition were designed using Zr-Nb alloys as the research object,and the microstructure evolution of the designed and alloyed alloys during aging under the combined effect of fine grain strengthening and spinodal strengthening and their effects on the mechanical properties of the alloys were investigated,and the main research contents and results are as follows.(1)According to the binary phase diagram of Zr-Nb alloy,three alloys with spinodal decomposition and higher strength and lower elastic modulus were designed with Zr-60 Nb,Zr-50 Nb and Zr-40 Nb compositions,and the microstructure and mechanical properties of these three alloys were characterized,and the results of the study showed that all three designed alloys underwent spinodal decomposition at suitable temperature aging,and the Nb content With the increase of Nb content,the yield strength of the alloys increased,among which the tensile yield strength of Zr-60 Nb reached up to 1207 MPa after cold rolling deformation and 1144 MPa after aging at 650°C for 0.5 h.The elastic modulus of Zr-50 Nb alloy was the lowest after aging at650°C for 2 h(67.6GPa).(2)Different temperatures were selected to age the three designed Zr-Nb alloys,and the effects of aging temperature on the evolution of microstructure and mechanical properties of the alloys were investigated.The results showed that after aging at 650°C,700°C and 750°C,the three alloys underwent different degrees of spinodal decomposition,and the volume fraction of the spinodal tissue gradually increased with the increase of temperature,the splitting of XRD satellite peaks became more significant,and the size of the deformed grains gradually grew;the mechanical properties of the alloys decreased with the increase of temperature,and the elongation increased with the increase of temperature.(3)The three designed Zr-Nb alloys were aged at 0.5h,1.0h,1.5h and 2.0h,and the effects of aging time on the microstructure evolution and mechanical properties of the alloys were investigated.The results showed that the spinodal decomposition of all three alloys was not obvious at 0.5 h of aging,and the volume fraction of the amplitude modulation organization started to increase gradually after 1.0 h of aging,and the phase size of the decomposition products also increased gradually with the increase of aging time;the grain size of the alloys increased with the increase of aging time;the mechanical properties of the alloys showed different patterns under the combined effect of spinodal strengthening and grain deformation recovery.