Using Roll Bonding And Annealing To Process Fe/Al Multi-layered Composites From Elemental Foils

Intermetallic compound Fe/Al, such as Fe3Al or FeAl, has the excellent resistance to sulphidization and structural stability in high temperature because of its special physical and chemical properties. Intermetallic compound Fe/Al is one of the potential candidate structural materials in high-temperature which are widely applied in aerospace and automobile, because it has high specific strength, intermediate temperature strength, abnormal relationship between yield strength and temperature, and it’s cheap in price.The whole study of using roll bonding and annealing to process Fe/Al multi-layered composites from elemental foils is financed by the Fundamental Research Funds for the Ministry of Education (Grant No.1000402003). This paper used the elemental foils to produce intermetallic compound Fe/Al through stacking, rolling and diffusion reaction. This paper analyzed the impact of rolling and heat treatment process on microstructure, the interface diffusion and phase transformation reaction in different process conditions, and achieved the optimal parameters. Based on the analysis of the formation mechanism for the edge crack and interface defects, the method of improving the quality of the shape and the rolling yield was proposed in terms of the metal flow and the compatible deformation. With this study, the following conclusions were achieved:1) Elemental foils have the important impact on the thickness of stratification and shape quality. The growth behavior of intermetallic compound Fe/Al is ideal after the heat treatment process when the thickness of iron foil is50μm and the thickness of aluminum foil is15μm. The multi-pass rolling can result in storing more deformation energy in the interface which will benefit the growth behavior of intermetallic compound Fe/Al.2) When the annealing process at the temperature of500℃for60minutes, the thickness of the intermetallic compound region is approximately2.6μm. The intermetallic compound region will thicken quickly when the annealing time increases. Inproving the annealing temperature has the great impact on accelerating the growth behavior of the intermetallic compound Fe/Al. When the annealing process at the temperature of600℃for60minutes, the thickness of the intermetallic compound region is approximately13.0μm.3) Platform area located on the both sides of Al matrix appears at the Fe/Al interface scanned by scaning electron microscope at the temperature of575℃for60minutes, and intermetallic compound FeAl3has formed at this time. As the temperature increases to600℃, the phase change process accelerates obviously, and intermetallic compound FeAl3and FeAl2appear at the same time.4) Considering the metal flow and the compatible deformation in the process Fe/Al multi-layered composites from elemental foils, what is can be finded is the incidental tensile stress accumulating and releasing periodically at the edge of elemental foils leaded to the formation of the periodic crack discovered by force analysis.