Effect of Molybdenum Addition on Microstructural and Mechanical Characterization of Highly Porous Steels

In this work, the influences of adding different amounts of molybdenum (0, 0.5, 1, 2, and 4 wt%) on the microstructure and mechanical properties of highly porous steels fabricated using powder metallurgical water-leachable space holder technique were studied. The microstructure of cell walls and morphologies of cells and micro-pores were evaluated using an optical microscope and scanning electron microscope equipped with X-ray energy dispersive spectroscopy. To evaluate the mechanical properties, compression tests were conducted on the highly porous steel specimens. The results demonstrated that about 90 wt% of urea granules are discontinuously removed during the multi-stage leaching process. The relative density of the highly porous steels was measured between the range of 0.18 and 0.22 and it increased by adding the molybdenum content. Ferrite, fine pearlite, and distributed molybdenum islands formed the microstructure of cell walls. The stress–strain curves contained linear elastic region, long saw-toothed plateau region, and fracture point. By changing the amounts of molybdenum from 0 to 4 wt%, mean modulus of elasticity, plateau stress, and density of energy absorption showed 0.75, 7.32, and 6.75 times improvement, respectively. Also, yield strength and failure strain revealed up–down behavior.