Effect of Cryogenic Treatment on the Microstructures and Mechanical Properties of Tempered Fe-2Ni-0.5C Metal Foams
摘要
In this study, Fe-2Ni-0.5C metal foams with pore sizes of 2 mm and a porosity of 54% were fabricated by pressureless powder space holder technique. The influence of cryogenic treatment on the tempered microstructure and mechanical properties of the alloy was investigated. The results revealed that the microstructure of quenched alloy was dominated by brittle martensite, leading to fracture and fluctuation in the compression curve with a low energy absorption capacity. The quenched metal foams followed by tempering at low (250 °C) and high (500 °C) temperatures, exhibited a microstructure consisting of tempered martensite and spheroidal cementite particles. Thus, tempering avoids fracture during compression and enhances the energy absorption capacity of the alloy. The application of cryogenic treatment prior to tempering facilitates the fine and dense precipitation of cementite during the high-temperature tempering process. As a result, the plateau stress and energy absorption of the cryogenically treated alloy were higher by approximately 30% compared to the untreated alloy. Moreover, low-temperature tempering after cryogenic treatment formed more tempered martensite, resulting in the alloy exhibiting a significantly higher compressive plateau stress (659 ± 16 MPa) and energy absorption capacity (310 ± 12 J/cm3). The results show the highest energy absorption capacity among the iron-based porous alloy reported thus far. The study provides a new solution for developing high-strength energy-absorbing materials and lightweight structures.