Heat Treatment Of Degradable Aluminum Alloy For Oil And Gas Field Development

Al-Ga alloy has potential application value in the development of oil and gas fields due to its degradability.However,the as-cast Al-Ga alloy has poor plasticity,difficult machining(cold working),and high machining cost and material consumption due to degradation due to water.Therefore,the goal of this paper is to explore the process of hot-extruded Al-Ga rods as cast pipes,and the research content includes the optimization of Al-Ga alloy heat treatment process and the research on the degradation performance after hot extrusion.First of all,the Al-8.5Mg-6Ga-5.8Sn alloy(bar)was separately solution treated+aging treatment,homogenization annealing treatment,and analysis of the structure and performance changes before and after heat treatment;secondly,the hot extrusion of the rod processing pipe,analysis changes in degradation performance and degradation products.The main research results of the paper are as follows:(1)The microstructure and properties of Al-Mg-Ga-Sn alloy in various states are analyzed.The results show that both the as-cast alloy and the heat-treated alloy contain black Alss phase,the bright white Mg₂Sn phase and the light gray Mg-Ga intermetallic compound,and the as-cast,annealed and hot extruded alloy also contain Sn elemental substance.With the increase of solid solution temperature and the extension of holding time,the content of the second phase of the solid solution alloy gradually decreased,and the fishbone becomes point.With increasing homogenization temperature and holding time,the dendrites in the annealed alloy gradually disappeared,and the light gray Ga₅Mg₂ phase continues to dissolve in Alss.The second phase in the parallel extrusion direction of the hot extruded alloy is uniformly distributed among the Al matrix in a fibrous shape,dendritic segregation is greatly improved,while the second phase in the v ertical extrusion direction is broken and unevenly distributed.(2)The influence of Al-Mg-Ga-Sn alloy hardness in various states was studied by means of Vickers hardness tester and high temperature hardness tester.The results show that the reduction of the segregation phase of the as-cast alloy through the heat treatment process reduces the grain size and increases the hardness.Increasing the proportion of bright white phase is helpful to strengthen the alloy by using Mg ₂Sn phase bias at grain boundary.The high temperature hardness test selects the suitable extrusion temperature of the as-cast alloy at 290?,and the hardness is 81.6 HV.The hardness of the tubular hot extruded alloy gradually decreases from the inner wall to the outer wall,and the highest hardness is 126.2 HV.(3)The electronic constant temperature stainless steel water bath and electrochemical workstation were used to test the degradation rate of Al-Mg-Ga-Sn alloy in 2%KCl solution at 70?and the polarization curve at room temperature.The results show that the order for the degradation rate is hot extruded state>cast state>annealed state>solid solution state.The higher the content of the second phase in the alloy structure,the coarser the grains,and the faster th e degradation rate.The corrosion potential of the annealed and solid solution alloys shifted positively,while the hot extruded alloy shifted relatively negatively,and the resistance became smaller as the corrosion potential shifted negatively.The degradation rate of the hot extruded state can reach 7.45 g/h·cm²,and the corrosion potential moves negatively to-1.495V.(4)Analysis of the components and corrosion morphology of the degradation products of the hot extruded Al-Mg-Ga-Sn alloy after reaction with pure water,2%KCl and 2%Na Cl solution at 70?.The alloy products are mainly Al O(OH)(boehmite)and Al(OH)₃ and there are also Sn and Ga simple substance.Due to the micro-battery effect formed between the Alss and Mg ₂Sn phases,the corrosion rate of the alloy is accelerated,and the corrosion pits diffuse from the second phase to the surroundings.