Fe-Al-Cr합금의 미세구조와 기계적 성질에 미치는 Mo과 Hf의 첨가 효과

Abstract

After Fe20Al6Cr intermetallic compound gaining Mo and Hf was manufactured using Opsprey Forming Process for practical use of Aluminum inter-metallic compounds, the microstructure and mechanical properties of the alloy as well as the skill of casting used by Osprey Forming Process were researched. FeAlCr intermetallic compound was manufactured by Osprey Forming Process in order to improve the ductile of FeAlCr intermetallic compound in room temperature and the working of the compound and to lower the cost of production. The microstructure of Fe20Al6Cr intermetallic compound was changed from the coarse equiaxed structure to the minute equiaxed one because of the addition of Mo and Hf. In addition, the effect of adding Mo and Hf for being minute of grain refinement was shown 0.1Hf < 0.5Hf < 1.0Hf. When the element of alloy is added to the order structure, it changes the microstructure because the optional replacement of the third element or the fourth element in the specific lattice point changes the interaction energy between the elements. When the both 1% Mo and 1% Hf are added to the basic alloy, Fe20Al6Cr, compared to Fe20Al6Cr, the phases of 4-5 elements alloys of Fe-Al-Cr-Hf and Fe-Al-Cr-Mo-Hf in which Hf is highly segregated in grain boundary decreasing Fe, Al, and Cr contents in grain are formed. As the result of analyzing XRD of Fe20Al6Cr intermetallic compound, FeAl phase was shown and it was known that the XRD aspect of B2structure had a superlattic peak not a basic peak. The rates of hardness and yield strength of Fe20Al6Cr intermetallic compound were increased after Mo and Hf had been added in it. The numeric value of microvickers hardness of Fe20Al6Cr alloy without Mo and Hf was 471 HV but the numeric values of Fe20Al6Cr1Mo0.1Hf, Fe20Al6Cr1Mo0.5Hf, and Fe20Al6CrlMo1Hf alloys, when Mo and Hf were added in them, are 489, 510, and 540 respectively increasing their hardness. In addition, when the third element was added in the results above, both hardness and strength of it were increased by showing precipitation hardening and solid solution hardening occurred by the second phase in grain and in grain boundary. The aspect of fracture surface of Fe20Al6Cr intermetallic compound represented the typical brittle fracture cleavage surface and if Mo and Hf were added in it, the aspect of fracture would be changed from cleavage into intergranular and the aspect of fracturesurface gaining 1Mo and 0.5Hf would be changed into the mixed form of intergranular and partially cleavage, the aspect of fracture surface gaining 1Mo and 1Hf would - Ⅴ -be changed into quasi-cleavage.