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在铸造Al-7Zn-2.5Mg-Cu合金中分别加入0.2%、0.5%、0.8%和1.2%的Al-5Ti-B细化剂,研究了细化剂加入量对合金的微观组织、抗拉强度和热裂倾向的影响。结果表明,Al-5Ti-B细化剂明显细化Al-7Zn-2.5Mg-Cu合金的组织。随着细化剂添加量的增加,晶粒尺寸先减小,后稍微增大,在加入量为0.8%时,晶粒尺寸最小,为66μm。随着晶粒尺寸的减小,Al-7Zn-2.5Mg-Cu合金的共晶体数量增多,抗拉强度增加,热裂倾向减小。抗拉强度与晶粒尺寸的关系为σb=47.22711+1325.35477×d-1/2,热裂倾向与晶粒尺寸的关系为H=41.73912+0.5733×d。共晶组织也影响合金的抗拉强度和热裂倾向。试验范围内,共晶组织增多,抗拉强度降低,热裂倾向先降低后升高。
Al-5Ti-B refiners were added into Al-7Zn-2.5Mg-Cu alloy by 0.2%, 0.5%, 0.8% and 1.2% respectively. The effect of the refiner on the microstructure, Intensity and thermal cracking tendencies. The results show that the microstructure of Al-7Zn-2.5Mg-Cu alloy is obviously refined by Al-5Ti-B refiner. With the addition of the refiner, the grain size decreases first and then increases slightly. When the addition amount is 0.8%, the grain size is the smallest, which is 66μm. With the decrease of grain size, the amount of eutectic Al-7Zn-2.5Mg-Cu alloy increases, the tensile strength increases and the thermal cracking tendency decreases. The relationship between tensile strength and grain size is σb = 47.22711 + 1325.35477 × d-1/2. The relationship between thermal cracking tendency and grain size is H = 41.73912 + 0.5733 × d. Eutectic structure also affects the tensile strength and hot cracking tendency of the alloy. Within the experimental range, the eutectic structure increased, the tensile strength decreased, and the thermal cracking tendency first decreased and then increased.