Effects Of Microalloying And TiC-TiB₂ Particles On Microstructure And Mechanical Properties Of Al-Cu Alloy By Twin-roll Casting

As a commonly used process for producing alloy strip,twin-roll casting(TRC)has the characteristics of low energy consumption,short process,few processes,green environmental protection and so on.However,since the TRC process is prone to central segregation that seriously affects the properties of the alloy during the production of ultra-thin strips,and this central segregation belongs to macro segregation,which cannot be eliminated in the subsequent heat treatment stage,the production and use of TRC ultra-thin strip are severely restricted.Especially in the production of high temperature resistant Al-Cu alloy thin strip,because the alloy contains a considerable amount of high temperature resistant phases,when these phases aggregate in the central segregation region,the mechanical properties of the alloy will be greatly reduced,resulting in the difficulty of preparing high temperature resistant Al-Cu alloy ultra-thin strip with qualified properties in industrial production.Therefore,in this paper,the ultra-thin high temperature resistant Al-Cu alloy strip was prepared by adding 0.1wt%Zr element and different contents of Mn element into the TRC Al-Cu alloy,and its as-cast microstructure heat treatment microstructure and mechanical properties at room temperature and high temperature were studied.Finally,the best high temperature performance was selected,However,Al-5Cu-0.8Mn-0.1Zr(ACMZ)alloy with the most internal defects should be optimized.Therefore,in this paper,Ti C-Ti B₂nanoparticles are added to ACMZ alloy as particle enhancer,and nano particle reinforced ACMZ alloy ultra-thin belt is prepared by using TRC technology.The effects of different contents of Ti C-Ti B₂nanoparticles on the as-cast microstructure,microstructure after heat treatment and mechanical properties at room temperature and high temperature of TRC ACMZ strip S were studied,and the following conclusions weredrawn:(1)After microalloying treatment,the columnar crystal length and deformation degree of TRC Al-Cu alloy increase with the increase of Mn content.After adding 0.8wt%Mn element and 0.1 wt%Zr element,there are almost no equiaxed crystals in the central area of TRC Al-Cu alloy,and the whole structure is composed of elongated grains.(2)With the increase of Mn content,the width of segregation zone gradually decreases into an obvious segregation zone,which reduces the mechanical properties of TRC Al-Cu alloy.The primary second phase on both sides of the segregation zone has different morphological characteristics,which are grid and flake respectively.(3)The increase of Mn content reduces the number of equiaxed grains,improves the precipitation of T phase during isothermal holding.With the increase of Mn element,a large amount of dispersed T phase precipitates in the alloy is precipitated.Through dispersion strengthening,the yield strength and tensile strength of the alloy at high temperature are improved and the plasticity of the alloy is reduced.(4)Nano Ti C-Ti B₂particles can form equiaxed crystals in the middle region of the alloy to inhibit the growth of columnar crystals,so as to prevent the aggregation of solute elements,enlarge the width between the upper and lower segregation bands,and reduce the size of the primary second phase.(5)Adding nanoparticles reduces the central segregation,decreases the conductivity of the alloy,and makes the distribution of solute elements in the alloy more uniform,so as to precipitate more dispersed T phases with more uniform and smaller size in isothermal holding.(6)When the content of nanoparticles is less,the number of new grains formed in the alloy is less.With the isothermal holding and solution aging treatment,the grain size increases obviously;With the increase of nano particle content,the number of grains formed in the alloy increases significantly.After heat preservation and solid solution aging treatment,the grain size in the alloy is uniform and obviously refined.(7)Nanoparticles improve the room temperature and high temperature properties of ACMZ alloy.After adding 0.3 wt%nanoparticles,the yield strength at room temperature has increased 34.9%,and the tensile strength has increased 14.7%;The yield strength of high-temperature tension has increased 22.9%,and the tensile strength has increased 33.7%.