Abstract

An academic methodology based for experimental evaluation of materials treatment is presented. The study is centered in an educational research emphasis about microstructure evaluation and heat treatments in steels samples machined according to ASTM E8 specifications. The uses of metallographic techniques and hardness/tensile tests for analyzing experimental variations due to structural changes are included. Different thermal treatments were applied on AISI-SAE 1018 steel specimens by raising the temperature until it reached the austenization state. Images were obtained with a Nikon NIS Elements computer programming, in order to observe the microstructure and identify the phases involved in each of the thermal treatments. For the hardness analysis, the round indenter of 1/16 in of Tungsten Carbide with a preload of 100 kg was used. A grain diameter of 3 to 4 µm was observed in both annealed and normalized sample, so it is assumed that the cold rolled or reference sample had a normalized condition. Both 41 and 67% in elongation and area reduction percentages, respectively, in the normalized samples were observed. The results allow identifying the correlation between microstructures and mechanical properties, providing an engineering educational approach for metallographic analysis and heat treatment schemes focused on the grain size interpretation, resilience and stress-strain curves. The described methodology provides an academic reference for the didactic evaluation of the main techniques associated with the treatment of materials for physics and mechanical engineering training.

Key words: Heat treatments, microstructure, tensile test, hardness, educational research.