7050铝合金圆锭超声铸造微观组织及热裂敏感性研究

【作者】 张雪；

【导师】 李晓谦；

【作者基本信息】 中南大学 ， 机械设计及理论， 2010， 硕士

【摘要】 半连续铸造是目前最常用的一种铸造方式,其过程是一个复杂的动态凝固过程,包含几何非线性、材料非线性等众多非线性因素。在铸造过程中容易产生各种铸造缺陷,如晶粒粗大、缩孔缩松、开裂、组织和成份偏析等。本文通过数值模拟和试验研究的方法,主要从微观组织和热裂纹敏感性两方面,探讨工艺参数和超声场对7050铝合金圆锭的影响。1、概述了7xxx铝合金半连续铸造的发展及研究现状,分析了铸造微观组织数值模拟的发展,总结了现有的几种模拟方法,分析了目前铸造热裂数值模拟与热裂判据的研究现状。2、进行了7050铝合金超声半连续铸造试验,对试验结果进行了总体分析,总结了超声场对铸锭组织、力学性能以及裂纹产生的影响规律。3、利用ProCAST软件的CAFE模块进行了铸造过程的微观组织模拟,建立了基于CAFE的数学模型,设置和选择了相关的模拟条件及参数,从而分析了不同工艺参数对7050铝合金圆锭微观组织的影响规律；同时通过探讨超声场对形核率和过冷度的影响,等效模拟了施加不同功率超声场对微观组织的影响。4、利用ProCAST软件的HCS模块进行了铸造过程的热裂纹敏感性模拟,采用了基于凝固补缩理论的热裂判据——RDG判据,设置和选择了相关的模拟条件及参数,从而得出了不同工艺参数和超声场对7050铝合金圆锭热裂纹敏感性的影响规律。更多还原

【Abstract】 Semi-continuous casting which relates to dynamic solidification process is the most popular casting way these days. It involves many nonlinear factors including geometry nonlinear and material nonlinear. It is liable to produce various casting defects, such as coarse grain, shrinkage cavity, shrinkage porosity, hot tearing, microstructure segregation and solute segregation. The effects of technological parameters and ultrasonic field on 7050 aluminum alloy ingot are studied by numerical simulation and experimental investigation, which mainly focused on microstructure and hot tearing sensitivity.1. The development and present status of 7xxx aluminum alloy semi-continuous casting are summarized. The microstructure numerical simulation of casting and some existing simulation methods are introduced. The simulation and criterions of hot tearing are also analyzed.2. The experiment of 7050 alloy ultrasonic semi-continuous casting is processed and the results are analyzed. The effects of ultrasonic field on microstructure, mechanic property and hot tearing formation are summarized.3. The microstructure of casting ingot is simulated by CAFE module which belongs to ProCAST. The mathematic model of CAFE is set up, meanwhile the correlative condition and parameters are chosen. The effects of different technological parameters on microstructure of 7050 aluminum alloy ingot are analyzed. The effect of ultrasonic on nucleation rate and undercooling is researched and the influences of different ultrasonic power on microstructure are also simulated.4. The hot tearing sensitivity in the casting process is simulated by HCS module which belongs to ProCAST, and the criterion of judging hot tearing formation-RDG criterion is chosen, which is analyzed based on the view of solidification and compensation. The effects of different technological parameters and ultra-sonic field on the hot tearing sensitivity of 7050 aluminum alloy ingot are also obtained.更多还原