First-principles Study On The Phase Stability And Elastic Properties Of Zr-Ti-Al-V Alloy

Since the 1960 s,with the increasing number of spacecraft launched by various countries,the space environment has become increasingly complex.The development of high-performance structural materials suitable for space environments has become an inevitable choice for the development of spacecraft in the future,with low density.The 47Zr45Ti5A13 V alloy with high strength,high ductility,high radiation resistance and high oxidation resistance is expected to replace high-strength steel as a key moving part and structural material in spacecraft.In this paper,the Zr-Ti-Al-V alloy is studied.The relationship between the mass fraction of alloy elements,phase structure and elastic properties in Zr-Ti-Al-V alloy is the core of the study.The effects of elemental composition and phase structure on the phase stability and elastic properties of Zr-Ti-Al-V alloy were studied in order to clarify the elemental composition,phase structure and phase of Zr-Ti-Al-V alloy.The relationship between stability and elastic properties provides a scientific basis for optimizing the composition design,processing and heat treatment of Zr-Ti-Al-V alloys.The research contents and results are as follows:(1)The total energy,unit cell structure,elastic properties and electronic structure of different Ti atom fractions and different structure Zr-Ti alloy systems were calculated by first-principles principle,and the mass fraction of Ti and the alloy phase in Zr-Ti alloy were analyzed.The effect of the structure on its phase stability and elastic properties.The results show that both the ? phase and the ? phase have stability in the Zr-Ti alloy,but the stability of the ? phase is higher than that of the ? phase due to the different phase structure,and the stability of the ? phase and the mass fraction of Ti in Zr-Ti alloy is positively correlated,and the stability of ? phase does not follow this rule.Due to the difference of phase structure,the ? phase of Zr-Ti alloy is generally higher than that of Zr-Ti alloy ? phase in strength and hardness.It is lower than the ? phase of Zr-Ti alloy;in the ? phase and ? phase of Zr-Ti alloy,the mass fraction of Ti has good strength,hardness and stiffness at 34.5%~87.5%,and the mass fraction of Ti The ductility is higher at 34.5% to 55.2%.Since the mass fraction of Ti in the 47Zr45Ti5Al3 V alloy is 45%,combined with the research results,the Ti composition in the 47Zr45Ti5Al3 V alloy can ensure the alloy has good strength and ductility.Properly increasing the mass fraction of Ti in the 47Zr45Ti5Al3 V alloy can further improve the strength and ductility of 47Zr45Ti5Al3 V alloy.(2)The total energy,unit cell structure and elastic properties of different alloying elements(Al,V)and the Zr-Ti-Al alloy system and Zr-Ti-V alloy system with different structures were calculated by first-principles principle.The relationship between the phase structure and elastic properties of Zr-Ti-Al alloy and Zr-Ti-V alloy with a certain mass fraction of Zr and Ti.The results show that Al is the ? phase stable element of Zr-Ti alloy,V is the ? phase stable element of Zr-Ti alloy;the mass fraction of Al in Zr-Ti-Al alloy has relatively good strength and hardness when it is 4~6.8%.And stiffness,and the higher the mass fraction of Al,the worse the ductility of Zr-Ti-Al alloy;the mass fraction of V in Zr-Ti-V alloy has relatively good strength,hardness and stiffness at 2.4%,and V When the mass fraction is 0 to 12%,the higher the mass fraction of V,the better the ductility of the Zr-Ti-V alloy.Since the mass fraction of Al in the 47Zr45Ti5Al3 V alloy is 5% and the mass fraction of V is 3%,the combination of the results of the study shows that the composition of Al and V in the 47Zr45Ti5Al3 V alloy can not only enhance the stability of the ? phase and ? phase but also ensure the 47Zr45Ti5Al3 V.The alloy has good strength and ductility.The mass fraction of Al and V in the 47Zr45Ti5Al3 V alloy can further optimize the mechanical properties of the 47Zr45Ti5Al3 V alloy.(3)The effect of phase structure of 47Zr45Ti5Al3 V alloy on its phase stability and elastic properties was investigated by first principles.The results show that the ? of 47Zr45Ti5Al3 V alloy is more stable than its ? phase,and the introduction of Al and V in 47Zr45Ti5Al3 V alloy not only improves the phase stability of ? phase and ? phase but also enhances its strength and ductility.The ? phase and ? phase of 47Zr45Ti5Al3 V alloy have good ductility,but due to the difference of phase structure,the ? phase of 47Zr45Ti5Al3 V alloy is higher than 47Zr45Ti5Al3 V alloy ? phase in strength and hardness,and is lower in ductility than Zr-Ti alloy ?.phase.On the whole,the composition design of 47Zr45Ti5Al3 V alloy can ensure the good strength and ductility of 47Zr45Ti5Al3 V alloy.The mechanical properties of 47Zr45Ti5Al3 V alloy can be further optimized by heat treatment to control the phase composition of 47Zr45Ti5Al3 V alloy.(4)Tensile test and XRD pattern analysis of 47Zr45Ti5Al3 V alloy samples treated with different temperatures were carried out to study the effects of ? phase and ? phase on the elastic properties of 47Zr45Ti5Al3 V alloy.The results show that when the ? phase content of the 47Zr45Ti5Al3 V alloy is 68.3%,the tensile strength reaches 1176 MPa when the ? phase content is 31.7%,and the tensile strength reaches 1256 MPa when the ? phase content of the 47Zr45Ti5Al3 V alloy is 8.8% and the ? phase content is 91.2%.The elongation is about 10.9%;when the 47Zr45Ti5Al3 V alloy is all ? phase,the tensile strength reaches 1067 MPa and the elongation is about 11.2%.The increase of ? phase in 47Zr45Ti5Al3 V alloy will increase the ductility of 47Zr45Ti5Al3 V alloy,but the strength will not follow this rule.The 47Zr45Ti5Al3 V alloy can be made to have high strength and high ductility by controlling the heat treatment process to change the phase composition in 47Zr45Ti5Al3 V alloy.The first principle study conclusions on the phase stability and elastic properties of 47Zr45Ti5Al3 V alloy are also demonstrated.