Indian Journal of Science and Technology

Abstract

Over the last decades the investigations have been actively under way to develop the methods, aimed at increasing the strength characteristics of metals. To increase the strength indicators it is most practicable to apply the metal processing technologies, focused on refining the grain structure. However, now the industry employs the processes, by applying which metals form clearly expressed coarse-grain structure, for example, casting. The fact that the casting manufacturing technologies are widely spread is related to their low cost of production. The cast items, in most cases possess coarsecrystalline structure, which affects negatively the chemical and the physical/mechanical characteristics of materials. Refining the coarse-grain structure represents a difficult (from the view point of technology and economic effectiveness) technical task. One of the most prospective approaches to refining the material grain structure is the way of grinding it at the stage of solidification upon melting. This can be achieved by introducing the additional particles in the molten pool, which perform the function of “micro-coolers” (crystallizing centers); they, merely by their presence, make obstacles for the movement of grain boundaries during crystallization. One more prospective method for structure refining is that of hot plastic deformation, when the structure is refined mechanically. The article gives an account of the process and of the results of the experiments to obtain castings with refined structure due to introducing the disperse particles in the melt at the casting stage. Part of the obtained castings underwent hot plastic deformation. While investigating the obtained materials the alteration of the microstructure in the castings has been estimated depending on the amount of introduced particles, and also the investigations on hardness and wear resistance alteration were undertaken both in cast and in deformed conditions.
Keywords: Disperse and Dispersive Hardening, Grain Refinement, Metal Hardness, Microstructure, Molded Pieces, Plastic Deformation by Forging, Strength, Wear-Resistance