Interface Bonding Mechanism of 2024/6061 Aluminum Alloy Bimetallic Casting Blank Subjected to Isothermal Compression

The present study conducted the isothermal compression of 2024/6061 aluminum alloy bimetallic casting blank using a Gleeble-3500 thermal simulator in the temperature range of 300-450 °C and strain rate range of 0.01-5 s −1 to clarify the interface bonding mechanism. The effect of temperature and strain rate on the stress was studied, and the strain-compensated constitutive model was established. The effects of element diffusion on the interface bonding were clarified. It is found that the stresses decrease with increasing compression temperature and decreasing strain rate. The stress softening behavior is attributed to the combined effect of strain hardening and dynamic softening. The material constants in constitutive model considering compensation of strain are calculated, and the modified constitutive model reflects a relative low predictability of the interface bonding behavior. The sub-grains with low-angle grain boundaries are transformed into the recrystallized grains with high-angle grain boundaries due to the DRX in the bonding interface. The interface recrystallized grains and microstructural reconstitution are the main interface bonding behavior. The diffusion of interface elements is accelerated and the width of bonding layer increases with increasing compression temperature and decreasing strain rate. The continuous distribution of element diffusion in the bonding interface is enhanced. The interface bonding mechanism of the bimetallic blank is mainly characterized by a metallurgical bonding effect.