【作者】 胡化文；

【导师】 陈康华；

【作者基本信息】 中南大学 ， 材料学， 2004， 硕士

【摘要】 在材料制备和加工过程中引入外场增强对过程和材料组织结构的调控是材料研究的前沿领域。本文研究了Al-Zn-Mg-Cu系超高强铝合金超声熔体处理和凝固的工艺方法,结合铸锭宏观与显微组织及其力学性能的考察,研究了作用效果和机理。 对7055铝合金熔体凝固过程作超声处理,发现超声作用可细化晶粒,结晶方式由树枝晶向等轴晶转变,凝固组织显示了半固态加工凝固的特征,但铸锭含少量夹杂和气孔。 对7055铝合金熔体作超声处理后进行重力模铸,铸锭组织观察表明,在630℃～710℃的温度下对熔体作超声处理均可细化铸锭晶粒。熔体经超声处理铸态均匀化合金与未经超声处理的合金相比,布氏硬度提高10%,伸长率由3.8%提高到7.7%,电导率和抗拉强度也有所提高。 7055铝合金熔体超声处理后半连铸,与熔体未经超声处理相比,铸锭凝固组织均匀,缺陷少,宏观开裂现象被抑制,且合金电导率、抗拉强度和伸长率有所提高。 采用水冷变幅杆对7055铝合金熔体作超声处理,可消除熔体对变幅杆的浸蚀,而且半连铸铸锭凝固组织更加均匀,均匀化后合金的布氏硬度、电导率及抗拉强度和伸长率均较无水冷变幅杆超声熔体处理的铸锭有所改善。更多还原

【Abstract】 It’s an advanced technology for the introduction of outfield in the fabrication and processing of materials to control the processing and the structure of the materials. This paper investigated the effects of ultrasonic treatment of melt and ultrasonic solidification on Al-Zn-Mg-Cu series ultrahigh strength aluminum alloys, Both the macro- and micro-structure of the cast ingots were analyzed, their mechanical properties were studied to discuss the effects and mechanisms of the ultrasonic treatment.Ultrasonic treatment during solidification of 7055 aluminum alloy results in dendrite-free grain structure and leads to the fining of grain structure. The structure of the cast ingots presents the character of semisolid solidification.Ultrasonic treatment of the 7055 aluminum alloy melt before gravity casting fined the grain structure in the cast at the temperature range from 630℃ to 710℃. Compared to the cast ingots without ultrasonic melt treatment, hardness of homogenized as-cast alloy increases by 10% and its elongation increases from 3.8% to 7.7%, meanwhile its electric conductivity and tensile strength improves respectively.The study on ultrasonic melt treatment of the 7055 aluminum alloy followed by semi-continuous casting confirms that ultrasonic melt treatment could uniform the cast structure, and reduce the defects in the cast, especially suppresses the cracking, meanwhile improves the electric conductivity、 tensile strength and elongation.By designing a water-cooled vibrator and applying it in the ultrasonic melt treatment of the 7055 aluminum alloys, the corrosion of the vibrator was eliminated. The structure of the 7055 aluminum alloy cast becomes more uniform. The hardness, electric conductivity and elongation of the cast are higher than the cast which melt is treated with no water-cooled vibrator.更多还原