Fe/Al异质金属接头界面组织演变、生长动力学及力学性能

Interfacial microstructure evolution,growth kinetics and mechanical properties of Fe/Al dissimilar metal joints

采用真空扩散连接方法研究Fe/Al异质金属接头界面组织演变规律、金属间化合物(intermetallic compound,IMC)生长动力学及力学性能。结果表明:焊接温度为550℃时,接头界面无IMC生成,当焊接温度超过575℃时,界面由Fe_(2)Al_(5)及少量FeAl_(3) IMC构成,且随焊接温度升高IMC层迅速长大。在120 min保温时间条件下,接头剪切强度随焊接温度的升高先增加后降低,当焊接温度为575℃时,接头剪切强度达到最大值37 MPa。在550~625℃范围内,基于热力学分析得出Fe_(2)Al_(5)的吉布斯自由能ΔG_(Fe-Al)最低,而FeAl_(3)的ΔG_(Fe-Al)次之,在接头界面处IMC生成顺序为Fe_(2)Al_(5)→FeAl_(3)。Fe/Al接头界面IMC的生长随焊接温度呈抛物线规律,其生长激活能为282.6 kJ·mol^(-1)。在575,600,625℃条件下,界面IMC的生长速率分别为1.13×10^(-14),3.59×10^(-14),1.21×10^(-13) m^(2)·s^(-1)。

The interfacial microstructure evolution,growth kinetics of the intermetallic compound(IMC)and mechanical properties of Fe/Al dissimilar metal joints were investigated by vacuum diffusion bonding.The results show that there is no IMC formed on the interface of the joint bonded at temperature of 550℃.When the bonding temperature exceeds 575℃,the interfacial region is composed of Fe_(2)Al_(5) and a small amount of FeAl_(3),and the thickness of IMC layer increases rapidly with the increase of bonding temperature.Under the bonding time of 120 min,the shear strength of the joint increases first and then decreases with the increase of the bonding temperature,and the shear strength of the joint reaches the maximum value of 37 MPa.According to thermodynamic theory,the Gibbs free energy change of Fe_(2)Al_(5) is the lowest in the range from 550℃to 625℃,and then followed by that of FeAl_(3),and the generated sequence of interfacial IMC can be:Fe_(2)Al_(5)→FeAl_(3).The interfacial IMC grow in a parabolic manner as a function of bonding temperature,and its growth activation energy is 282.6 kJ·mol^(-1).The growth rates of IMC at the interface are 1.13×10^(-14),3.59×10^(-14),1.21×10^(-13) m^(2)·s^(-1) at 575,600,625℃respectively.