摘要
采用考虑热机耦合效应的刚塑性有限元方法,对正方体形7075铝合金的锻造过程和晶粒细化过程进行了数值模拟,所采用的晶粒细化模型为Yada模型.结果表明,锻件内的应力、应变、应变速率、温度分布不均,模型中心区域为易变形区,4个纵向棱边区和以上下接触表面为底面的接触锥形区为难变形区.细化首先开始于易变形区,再相继扩展到纵向棱边区和接触锥形区.应变速率和温度是决定晶粒尺寸的主要因素.增加应变速率,可使晶粒尺寸变小,但高应变速率使得锻件升温;而温度升高,使得晶粒尺寸长大.有利于晶粒细化的锻造工艺条件为:温度350℃～400℃,应变速率70 s-1～100s-1,道次压缩比20%～25%.讨论了Yada模型的局限性,指明了它的适用范围.
Rigid-plastic finite element method considering, thermo-mechanical coupling was used to investigate the thermal forging process of a cubical-shaped 7075 aluminum alloy piece, and the Yada model was adopted to calculate the grain refinement in the process. The simulation results show that the distribution of stress, strain, strain rate and temperature of the forging piece are not uniform, and according to the distribution of these physical quantities, the forging piece can be divided into four characteristic zones: the center ellipsoidal zone, the contact edge zone, the vertical edge zone and conical contact zone, where the first two zones are easy to deform, and the remained two zones are difficult to deform. The grain refinement begins from the center ellipsoidal zone, and then gradually expands to the vertical edge zone and conical contact zone. The comparison analysis of different forging parameters shows that temperature and compression strain rate is the major forging parameters controlling grain size. The grains of 7075 aluminum alloy can be further refined. with the increase of compression strain rate, but high compression strain rate will bring the excessive heat that will make grains to grow. Then a set of suggested forging parameters are given as follows, the initial temperature should be 350 degrees C similar to 400 degrees C, the compression strain rate should be 70 s(-1)similar to 100 s(-1), and the compression ratio should be 20%similar to 25%. And finally, the limitation and application region of Yada model are also discussed.
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2006年第4期642-646,共5页
Rare Metal Materials and Engineering
关键词
晶粒细化
热锻造
7075铝合金
刚塑性有限元法
grain refinement
thermal forging
7075 aluminum alloy
rigid-plastic finite element method
