The Mechanisms of Nano-AlN Content in the Microstructure and Mechanical Properties of Fe-25Mn-9Al-8Ni-1C-0.2Ti Alloy

In order to design a high-strength, tough alloy for structural components, Fe-25Mn-9Al-8Ni-1C-0.2Ti-xAlN (x = 0, 0.25, 0.5, 0.75, and 1 wt%) alloys are prepared by powder metallurgy combined with vacuum arc melting. It can be seen from microstructure that the AlN/Al preform obtained by homogenizing mixing followed by vacuum pressureless sintering is added to the arc melting in the form of raw materials, and the AlN phase can exist stably and be uniformly distributed in the matrix. The main phases of the alloys are composed of austenite, ferrite, and TiC. With the increase of AlN content, the ferrite content is decreased and the grains are refined. The distribution of ferrite grains is changed from network to needle-like and dot-like morphology. Mechanical property test results reveal that the addition of the nano-AlN can maintain the stability of the tensile strength while significantly improving its elongation after fracture. Specifically, when the AlN content is 0.5 wt%, the elongation after fracture reaches the maximum value of approximate to 55.8%, representing approximate to 98.5% improvement compared to the matrix alloy. It is attributed to the promotion of slip line formation by nano-AlN, resulting in a higher density of slip lines within the alloy.