Interface microstructure evolution and mechanical properties enhancement of lamellar TC11 alloy under electromagnetic shocking treatment

Abstract

Interface microstructure plays a key role on the mechanical properties of commercial alloys; however, traditional thermomechanical processing cannot achieve its targeted modification. Herein, a novel electromagnetic shocking treatment (EST) deftly utilizing electromagnetic pulse energy was carried out to selectively tailor the interface microstructure and further enhance the mechanical properties of forged lamellar TC11 alloys. Tensile properties and impact toughness of TC11 alloys were investigated by tensile test and Charpy impact test, respectively. SEM, EBSD, and TEM were used to characterize the phase, grain, and interface complexion variation. The results showed that, with the maximum temperature of alloy sample surface being limited to 354 K, with increasing peak current density, the strength and impact energy of TC11 alloys first increased and then decreased. For EST1 samples with a lower peak current density and sample surface temperature, spheroidization at prior β grain boundaries (GBs) and phase transformation between α and β phases occurred, phase boundary films (PBFs) were frequently observed and α'' phase was detected at PBFs, indicating the occurrence of interface wetting during EST1. It led to the increase in tensile properties and impact energy of alloy samples. Evolution mechanism of spheroidization at prior β GBs and phase transformation between α and β phases were explored in detail. EST-induced interface pre-melting led to the migration, segregation, and redistribution of solute atoms, which promoted phase transformation. It also caused interface migration and then facilitated spheroidization. Next, for EST2 samples with a slightly higher peak current density and sample surface temperature, grains underwent slight coarsening, which mainly contributed to the slight decrease in tensile properties and impact energy of the alloy samples. This study demonstrates that EST can serve as a novel method for targeted regulation of the interface microstructure and further improvement in mechanical properties of TC11 alloys.