摘要
相比于传统的锻造、挤压等工艺,剧烈塑性变形工艺的应变量较大,在细化晶体组织、强化合金力学性能等方面有更显著的效果,在工业生产中也得到较广泛的应用。而相比于等径角挤压、累积轧制等对所加工材料的尺寸有较大限制的剧烈塑性变形工艺,多向锻造更适用于加工较大体积的块体材料。同时多向锻造具有模具结构简单、加工方法简便、适用性强等特点而区别于其他剧烈塑性变形工艺。近年来,多向锻造在强化铝合金组织与性能方面得到较为广泛的研究。多向锻造工艺在加工铝合金过程中的影响因素较多,包括初始晶粒度、温度、应变速率、摩擦因数、第二相粒子的尺寸及分布等,可见确定出最佳且系统化的技术参数的难度较大;多向锻造铝合金过程中的晶体组织的细化机制、第二相粒子对金属组织及性能的作用机制较为复杂。近年来,研究者们深入研究了多向锻造过程中金属流动规律及变形组织运动规律等内在因素、温度与应变速率等环境因素对铝合金组织及性能的影响。此外,将有限元模拟技术与剧烈塑性变形工艺相结合也是研究的热点内容,通过有限元数值分析法模拟多向锻造过程可以为实际的研究及试验提供较为可靠的依据。研究发现,多向锻造过程中的晶体组织细化机制与加工过程中的总应变量有关,随着总应变量增大,影响及促进晶体组织细化的机制不同;采用对三组对称面循环锻压的方法得到的晶体组织更致密、更均匀,这与多向锻造过程中的金属流动有关;第二相粒子对铝合金组织的影响除了与其尺寸及分布相关外还与温度有关,即第二相粒子的状态会随着温度的升高而有所变化,进而对铝合金组织及性能的影响也发生变化。通过多向锻造工艺细化铝合金晶体组织、促进其均匀性增强的同时,铝合金的抗腐蚀性、抗剥落腐蚀及超塑性等性能也得到改善。本文概述了多向锻造的工艺过程,重点介绍了该工艺在铝合金中的研究现状,分析了多向锻造工艺的晶粒细化机制及其对铝合金显微组织与性能的影响,最后探讨了多向锻造工艺尚存在的问题与未来的研究方向。
Compared with the forging, extrusion and other traditional plastic deformation methods, the strain of the severe plastic deformation(SPD) is large. The SPD has better effects in refining the crystal structure and strengthening the mechanical properties of the alloy, and is widely used in industrial production. And compared with equal channel angular pressing (ECAP), accumulative roll bonding(ARB), and other SPD methods, multi-directional forging(MDF) is more suitable for processing larger bulk materials. MDF has many advantages like its simple mold structure, simple processing and good applicability, which is different from other SPD methods. In recent years, it has been widely researched on the microstructure and properties of aluminum alloys by multi-directional forged (MDFed). There are many influencing factors in the MDF process of aluminum alloy, including initial grain size, temperature, strain rate, friction factor, size and distribution of second phase particles, etc., so the most suitable and systematic parameters are hard to be determined. The refinement mechanisms of the crystal structure and the influence of the second phase particles on the metal structure and properties are complicated during the process of MDF of aluminum alloy. In recent years, researchers have researched the influence of internal factors such as the metal flow and the motivation of the deformation structure, and the environmental factors such as temperature and strain rate on the microstructure and properties of aluminum alloy during the process of MDF. The combination of finite element method (FEM) and SPD process is a hot topic in recent years. The simulation of MDF by FEM can provide a reliable basis for practical research and experiment. It is found that the mechanisms of the crystal refinement are related to the strain in the process of MDF. As the strain increases, the mechanisms of affecting and promoting the refinement of the crystal structures are different;the crystal structures obtained by method of forging three sets of symmetry planes in each pass are better, which is related to the metal flow in the MDF process;the influence of the second phase particles on the microstructure of aluminum alloy is related to temperature in addition to its size and distribution, and the state of the second phase particles changes with increasing temperature, and its effect on the microstructure and properties of aluminum alloy also changes. The MDF refines the crystal structures of aluminum alloy and promotes its uniformity, while the properties such as corrosion resistance, flaking corrosion resistance and superplasticity are also improved. This paper outlines the process of MDF and the research status of the process in aluminum alloy, and analyzes the grain refinement mechanisms of MDF process and its influence on the microstructure and properties of aluminum alloy, finally, discusses the problems still exist in the MDF process and the future research direction.
作者
王云鹏
胡嘉玮
许小云
刘道峰
蒋洪章
王晓勇
颜银标
WANG Yunpeng;HU Jiawei;XU Xiaoyun;LIU Daofeng;JIANG Hongzhang;WANG Xiaoyong;YAN Yinbiao(School of Materials Science and Engineering,Nanjing University of Science and Technology,Nanjing 210014;Heilongjiang North Tool Co. Ltd,Mudanjiang 157013;Nanjing Supufu Metal Products Co. Ltd,Nanjing 210014)
出处
《材料导报》
EI
CAS
CSCD
北大核心
2019年第13期2266-2271,共6页
Materials Reports
基金
国家部委基金资助项目(C182100C001)~~
关键词
多向锻造
铝合金
晶粒细化
显微组织
multi-directional forging
aluminum alloy
grain refinement
microstructure
