HTCR (High Throughout Casting and Rolling) is a new type of high-efficiency aluminum alloy sheet and strip billet production process, which has the advantages of high flow rate, short process, energy saving and environmental protection, and has broad development prospects. 5052 aluminum alloy is an alloy that cannot be strengthened by heat treatment. It has good formability, corrosion resistance, weldability, high fatigue strength and medium static strength. It is used to manufacture sheet metal parts of transportation vehicles, ships, containers and Street light brackets, etc.
At present, the 5052 aluminum alloy can be produced by the HTCR process. The casting speed of this process is fast and the homogenization annealing process is omitted before hot rolling, so that the microstructure and recrystallization process of the plate produced by it and the plate produced by the hot rolling billeting process are different. There is an obvious difference, adding intermediate annealing before cold rolling of the plate can reduce this difference to a certain extent. In this paper, the effect of adding intermediate annealing on the microstructure and recrystallization process of 5052 aluminum alloy sheet produced by HTCR process was studied.

1 Experimental materials and methods The experimental materials are 5052 aluminum alloy plates with a thickness of 7.2 mm produced by HTCR process. The chemical composition of the alloy is shown in Table 1.

The 5052 aluminum alloy plates with a thickness of 7.2mm are divided into two groups. One group of plates is directly cold-rolled to 1.8mm, and then annealed to complete recrystallization; crystallization. In the experiment, a box-type resistance furnace was used to complete intermediate annealing (480℃×8h, air cooling) and recrystallization annealing (350℃×3h, air cooling).
A metallographic sample was prepared by selecting a section parallel to the rolling direction (RD) of the above plate, and the microstructure of the sample was observed with a Leica DM4000M optical microscope. The EDS analysis was completed by ZEISSULTRA55 thermal field emission scanning electron microscope, and the grain size distribution was tested by the EBSD accessory of the scanning electron microscope.
Macrotexture XRD test was carried out on PANalytical high-resolution diffractometer X'pertMRD, using Schulz backscattering method to measure the diffraction pattern of the 1/4 thickness layer of the plate, and obtained (111), (200) and 1 The grains of the cold-rolled sheet treated by the intermediate annealing are strip-shaped, and the grains of the cold-rolled sheet treated by the intermediate annealing are elongated. The cold-rolled sheet with intermediate annealing has smaller grain size and more grain boundaries; grain boundaries are favorable positions for recrystallization nucleation, and more grain boundaries are conducive to the completion of the recrystallization process. From the grain size distribution in Figure 2, it can be seen that the recrystallized grain diameters of the non-intermediately annealed sheet are mainly distributed in the incomplete pole figures of the 12-(220) crystal planes, and the three incomplete pole figures are obtained by the series expansion method. The ODF orientation distribution function is calculated in the figure and represented by φ2=45° and φ2=90° cross-sectional views.
The cold-rolled plate to a thickness of 1.8mm is wire-cut into small samples with a size of 10mm×10mm for microhardness testing. The microhardness test is completed on the HXD-1000TMSC microhardness tester, and the downforce used in the test process is 50g. , the holding time is 15s.