同步低温原位合成7075铝基复合材料半固态浆料及其流变成形机制研究

7XXX series aluminum alloy is used extensively in the structure spare for aircraft and means of transport. Broad crystallization temperature and big difference in specific gravity between the precipitated phase and the matrix, which caused difficult filling, coarse microstructure and obvious macro-segregation. It is the goal of material researchers to cast wrought aluminum alloys directly into near-net-shape components. In-situ reaction technology has created favorable conditions for the rheological forming, but the high temperature of in situ synthesis process, easy burning of alloys and uneven distributed of the particles limit its development. In situ reaction is elicited to help with the preparation TiB2/7075 semi-solid composite slurry at low temperature by using ultrasonic energy. The high pressure can crush grains and particles, and improve the wetting and purify the microstructure. Low temperature of semi-solid can keep the uniformity of particles, and reduce material oxidized loss. Thermodynamics of in-situ synthesis at the semi-solid temperature, spheroidizing mechanism of grains under in situ particle and ultrasonic stirring and migration mechanism of particle in the semi-solid slurry will be studied. It is expected to accomplish the particle synthesis, microstructural refinement and melt refining at the same time during the slurry preparation. The implementation of the project is beneficial to shorten the preparation technology and reduce energy consumption. The research can also improve product quality and promote the practical application of semi-solid forming technology, which has extremely important theoretical and practical significance.

7xxx系铝合金广泛应用于飞机、交通运输工具中的重要结构件。由于这类合金结晶范围宽、析出相与基体之间比重差异大，因此易造成难以充型、组织粗大和明显的宏观偏析。将变形铝合 金从液态直接近净成形为零件一直是材料工作者追求的目标，原位反应技术为其流变成形创造了有利条件。但原位合成工艺温度高、合金易烧损，增强体分布不易均匀。本课题采用低温下超声能量辅助引发原位反应制备TiB2/7075复合材料半固态浆料，利用超声高压破碎颗粒与晶粒、改善润湿和净化组织，借助半固态低温保持颗粒分散、降低材料氧化。研究半固态低温原位合成颗粒的热力学，晶粒在原位颗粒和超声搅拌双重作用下球化机理，颗粒在半固态浆料中迁移运动机制，有望实现半固态温度下颗粒合成、破碎细化、熔体精炼、组织均匀化的浆料制备同步化过程。项目的实施有利于缩短制备工艺，降低能源消耗，提高产品质量，推进半固态成形技术实用化均具有极其重要的理论和现实意义。

7xxx系铝合金广泛应用于飞机、交通运输工具中的重要结构件。由于这类合金结晶范围宽、析出相与基体之间比重差异大，因此易造成难以充型、组织粗大和明显的宏观偏析。将变形铝合 金从液态直接近净成形为零件一直是材料工作者追求的目标，原位反应技术为其流变成形创造了有利条件。但原位合成及浆料制备温度高，浆料制备工艺复杂，制备过程中颗粒易沉降而不均匀。本课题采用原位合成TiB2/7075复合材料，并结合低温浇注或吸取技术制备半固态流变浆料。研究原位颗粒含量变化对颗粒大小、形核能力、晶粒尺寸、熔化特征的影响，液态和半固态条件下颗粒含量对复合材料黏度的影响，以及颗粒的沉降行为及半固态浆料组织演变规律。通过复合材料中原位颗粒与形核能力、晶粒尺寸、熔化性能的研究，进一步明确了原位颗粒合成规律和细化效果，为复合材料增强提高新的指导；通过采用三个方法制备半固态浆料，进一步丰富了浆料制备的内涵和简化了制备工艺；通过复合材料全液态和半固态下熔体的黏度和沉降规律研究，为颗粒对不同状态下材料组织性能影响提供了新的思路和知识点，进一步丰富了流体理论。总之，项目的实施有利于缩短制备工艺，降低能源消耗，提高产品质量，推进半固态成形技术实用化均具有极其重要的理论和现实意义。