In this study, a twin-roll casting sheet of 6061 aluminum alloy was cooled using furnace, asbestos, air, wind and water. The effect of cooling rate on the microstructure and properties of twin-roll casting 6061 aluminum alloy sheet were studied. Optical microscope, scanning electron microscope, X-ray diffraction, microhardness tester and universal tensile machine were used to observe the microstructure and properties of twin-roll casting sheet of 6061 aluminum alloy. The results show that the higher the cooling rate, the smaller the grain size of the alloy and the smaller the number of precipitated phases in the matrix. Uniform grain size of the alloy could be obtained at a stable cooling rate. The hardness, tensile strength and elongation of the twin-roll casting sheet increased with cooling rate. Under wind cooling condition, the twin-roll casting sheet demonstrated excellent comprehensive performance, i.e., 88 MPa of yield strength, 178 MPa of tensile strength and 15% of elongation, respectively. A quantitative Hall–Petch relation was established to predict the yield strength of 6061 twin-roll casting sheets with different grain sizes and cooling rate.

In this work, Thermo-calc thermodynamic calculations, Castep first principles calculations and other calculations were used to design the alloy compositions, four Mn, Zr composite microalloyed cast 6061 aluminum alloys were prepared using horizontal twin roll casting. At the same time, with the help of Optical Microscope (OM), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Tensile Testing Machine and other testing equipment, the microstructure and mechanical properties of the sheets were be characterized. The effects of Mn, Zr composite microalloying on the organization and high-temperature mechanical properties of 6061 aluminum alloy cast-rolled sheets were discussed. The results showed that Mn, Zr composite microalloying has effectively improved the uneven organization in the alloy, defected such as partial aggregation of iron-containing phases, while promoted the generation of α-AlFeMnSi phase, β^″ phase and Al₃Zr-L1₂ phase, significantly strengthened the sheet. The β^″ phase and Al₃Zr phase are thermally stable and can improve the high-temperature mechanical properties of the alloy. The cast-rolled sheets with co-addition of Mn and Zr had better overall mechanical properties. Compared with the original sheet, the yield strength and tensile strength of the sheet increased by 67.25% and 27.97%, respectively, and the high-temperature yield strength increased by 25.91% compared with that at room temperature.

Three kinds of 6061 aluminum alloy cast-rolled plates with Mg/Si mass ratios of 1.23, 1.45, and 1.7 are prepared using NF6–300 vertical twin-roll casting and rolling mill. Metallurgical microscope (OM), x-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), room temperature tensile test, and other analysis methods studied the influence law and mechanism of Mg/Si ratio on the microstructure and texture of 6061 cast-rolled sheet. The best Mg/Si ratio cast-rolled sheet is then analyzed for formability. Research indicates that with increasing Mg/Si ratio, the grain size shows first decreasing and then increasing trend. Morphology of precipitated phases at the edge and the central of the sheet are different, however, the texture type has no obvious change, and a strong {112} 〈110〉 texture and weaker rotating cube {001} 〈110〉 texture is always observed. When the Mg/Si ratio is 1.45, the average grain size is the smallest, the edge size is 39.78 μm, the central size is 31.31 μm, and the precipitated phase is evenly distributed at the edge and central of the cast-rolled sheet. In addition, the elongation reaches 8.9%, the n-value is 0.072, and the r-value is 1.161 when the cast-rolled sheet reaches 90° along the cast-rolled direction under T6 state heat treatment.