Homogenization System Influence On Microstructure And Mechanical Properties Of 7055 Aluminum Alloy

Ultra-high strength aluminum alloy7055is widely used in aerospace. During industrial producing process, it is easy to generate non-equilibrium solidified eutectic phases on the grain boundary for the high content of zinc and the fast cooling rate. The solute segregates seriously in the grain of the ingot, it is prone to produce internal stress. With the increasing demands of aerospace for the thick plate of ultra-high strength aluminum alloy, the ultra-high strength aluminum alloy is required to be with better processing performance, lower quench sensitivity and recrystallization percentage. So the homogenization treatment of the aluminum alloy7055is necessary, which can eliminate the non-equilibrium solidified eutectic phases and the ingredient segregation, as well as obtain uniformly dispersed and small coherent Al3Zr particles in the matrix of the alloy. Meanwhile the alloy obtains lower quench sensitivity and recrystallization. The influence of the homogenization treatment on the microstructures and mechanical properties of the aluminum alloy7055is studied, the main conclusions are as follows:(1) The best single-stage homogenization treatment is468℃/24h and the best two-stage homogenization treatment is468℃/24h+473℃/8h. With the rising of the homogenization heating rate and homogenization insulation temperature, as well as the extention of the homogenization time, the non-equilibrium eutectic phases existed in the ingot are eliminated gradually.(2) The alloy homogenized at264℃/4h,30℃/h+468℃/24h and408℃/4h,30℃/h+468℃/24h can obtain uniformly and dispersive distributed coherent Al3Zr particles. But the size of coherent Al3Zr particles is smaller in the alloy homogenized at264℃/4h,30℃/h+468℃/24h, which is in favour of inhibiting the recrystallization after solution treatment.(3) After hot rolling, the grains are elongated along the rolling direction in the aluminium alloy7055, which is treated with different homogenization institution. The alloy which is homogenized at264℃/4 h,30℃/h+468℃/24h can obtain the lowest recrystallization percentage. Bulky indissolvable Al2CuMg phases and Al7Cu2Fe phases are investigated in the recrystallized grains after solution treatment.(4)The alloy which is homogenized at264℃/4h,30℃/h+468℃/24h can obtain the highest yield strength and the alloy which is homogenized at468℃/24h,10℃/h+473℃/4h can obtain the highest tensile strength, the alloy which is homogenized at408℃/4h,30℃/h+468℃/24h can obtain the highest elongation.