Precipitation of Carbides in FeCr15Alx Alloys with Different Heat Treatments Studied by Internal Friction Technique

Fe-Cr-based alloys have great potential for large-scale vibration and noise reduction. Appropriate heat treatment is important for improving their damping capacity. However, M23C6-type carbides are common grain boundary precipitates during the heat treatment process, and can affect both damping behavior and mechanical properties. In this work, the effects of Al content and annealing temperature on the microstructure, internal friction (IF), room temperature damping capacity, and tensile properties of Fe-15Cr-(0-4) Al (wt.%) alloys were investigated. When annealed at 800 °C, Al addition can suppress grain boundary precipitation, and no obvious intergranular precipitates were observed in the S2Al-S4Al alloys. The ultimate tensile strength also increased with Al addition, and the S4Al alloy exhibited a 34% higher strength than S0Al while retaining an elongation of 47.7%. The maximum damping value increased with Al addition. However, annealing at 1000 °C promoted continuous grain boundary carbide formation and reduced the elongation. These results indicate that the S4Al alloy annealed at 800 °C provides a favorable balance between damping capacity and mechanical properties.