Effect of Al-5Ti-1B Adding Position on Microstructure and Mechanical Properties of 8079 Aluminum Alloy Cast-Rolled Plate

The 8079 aluminum alloy plate of 1050 mm×7.0 mm was directly cast and rolled with electrolytic aluminum liquid.The micro structure was characterized by optical microscope（OM）,scanning electron microscope（SEM） and energy spectrum analyzer（EDS）,and its mechanical properties were tested by tensile test.The results show that when the grain refiner Al-5 Ti-1 B is added into the chute about 10-12 cm away from the outlet of the on-line purification,degassing and impurity removal device,the grain structure of the sample is uneven,obvious pinholes appear,and granular inclusions appear inside the hole.The average tensile strength is 87.3 MPa and the elongation is 11.0%.When the Al-5 Ti-1 B is added into the chute 15-17 cm away from the outlet of the static furnace,the grains of the sample are fine and uniform without obvious pinholes and inclusions.The average tensile strength is 129.7 MPa and the elongation is about 36.7%.It is found by energy spectrum analysis that the particles inside the pores are mainly formed by the aggregation and precipitation of TiB₂ particles and Al₃ Ti.In the production process of cast-rolled plate,Al-5 Ti-1 B is added to the chute 15-17 cm away from the outlet of the static furnace,which can effectively prevent the coarse-grained structure and inclusions,and improve the structure and performance of the cast-rolled plate.