Microstructure And Property Control Of 2024 Aluminum Alloy For Marine Engineering

With the increasing consumption of oil and natural gas,the shallow surface resources in the crust are gradually exhausted.The exploration and exploitation of marine oil and gas resources has become an inevitable trend of resource development and utilization.Compared with the traditional steel drill pipe,the aluminum alloy drill pipe has the characteristics of high specific strength,low density,strong corrosion resistance,non magnetism,and small friction resistance with the hole wall.Under the same power of the drilling machine,the aluminum alloy drill pipe can reach the depth that the steel drill pipe cannot reach.It also has great advantages in deep-sea drilling,deep well,ultra deep well and sour gas well drilling and production.At present,the research on aluminum for offshore oil and gas exploration in China is still lower than the world level,and some key structural aluminum alloys still rely on imports.The short plate of 2024 aluminum alloy used in offshore drilling platform in China is due to its low hardness,low wear resistance,low strength and weak bending and torsion resistance.In this paper,by adjusting the composition and heat treatment process of 2024aluminum alloy for marine engineering,using the analysis and test methods of X-ray diffraction(XRD),metallographic microscope,macro hardness tester,scanning electron microscope(SEM),universal tensile testing machine,the influence rule and mechanism of different Zn content and different rare earth Yb content on the structure and properties of2024 aluminum alloy are studied,and the solution temperature and solution time are discussed The effects of heat treatment parameters such as aging temperature,aging time and so on on on the structure and properties of the alloy were optimized to optimize the alloy composition ratio and heat treatment process combination with the best comprehensive properties,so as to improve the comprehensive properties of 2024 aluminum alloy and provide the possibility for 2024 aluminum alloy to be used in offshore drilling platform.The results show that when the content of Zn is 0.25 wt%?1.0 wt%,with the increase of Zn content,the grain refinement effect of 2024 aluminum alloy is enhanced.When the content of Zn is 0.75 wt%,the hardness of 2024 aluminum alloy can reach 78.8 HRB,but when the content of Zn reaches 1.0 wt%,complex Al₇Cu₂Fe second phase will appear,which will affect the properties of the alloy.Solution temperature and solution time have a significant effect on the effect of the second phase dissolving into?(AL)matrix.By analyzing the number,morphology and size of al2cu and Al2Cu Mg phases,it can be seen that when the solution temperature is 455??515?,with the increase of solution temperature,the solution effect increases,the second phase of fine particles gradually completely dissolves into the matrix,the second phase of coarse particles gradually refines,and 2024 aluminum alloy is hard When the solution temperature is too high,the grains tend to grow.When the solution time is 4?6 h,the longer the solution time is,the fuller the solution is,but the coarsening of the structure is accompanied.The results show that the best solution process is 495?/5 h water quenching.After the treatment,the?(AL)matrix structure of 2024 aluminum alloy is uniform and fine,the solution effect is good,and the hardness reaches 88.9 HRB.With the increase of aging temperature,the precipitation effect of Al₂Cu and Al₂Cu Mg phases is obvious,and the hardness increases first and then decreases.When the aging process is195?/12 h,2024 aluminum alloy with Zn content of 0.75 wt.%shows the best comprehensive mechanical properties,with hardness,elongation and tensile strength of 93.0HRB,10.3%and 353 Mpa,respectively.Based on the optimal content of 0.75 wt.%Zn,three kinds of rare earth Yb were added to 2024 aluminum alloy.It was found that Al_7.4Cu_9.6Yb₂ phase was formed in 2024 aluminum alloy after adding 0.1 wt.%Yb,and the grain was refined.The modification mechanism of Yb was studied.Through single-stage optimization of solution+aging treatment process,it is finally determined that 495?/5 h solution+195?/12 h aging treatment is the optimal heat treatment process for 2024 aluminum alloy with three Yb additions.Through the comparison of tensile properties,the best addition of Yb is 0.10 wt.%Yb.After the optimal solution aging process,the alloy has good comprehensive mechanical properties,the tensile strength reaches413 Mpa,and the elongation reaches 12.8%.