EFFECT OF SOLUTION HEAT-TREATED ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF 27MN-4SI-2AL-NB-TYPE STEEL

The tests on high-Mn of 27Mn-4Si-2AI-Nb type steel were carried out. The steel was solution heat-treatment at different temperatures in a range from 900 °C to 1200 °C. The tensile testes had performed at room temperature under a strain rate of 2.5·10^-3s^-1on of the flat specimens were 6.35 mm in length and 3 mm in diameter and a gauge length of 25 mm. Effect of different grain size on microstructure and strain hardening behavior of high-Mn steel solution heat-treated was analyzed. The strength properties increase considerably with a decrease of grain size from 360 urn to 20 urn, where in the critical grain growth took place between 1000 °C and 1100 °C. The inverse relationship was confirmed between the grain size and ductility. The uniform elongation was increasing from 35 % to 45 % along with the increasing of grain size in the temperature range from 900 °C to 1100 °C and dramatically decreasing at the temperature 1200 °C to the 23 % by grain size 360 urn. Aluminium has segregated on the austenite grain boundaries in steel was solution heat-treated at 1200 °C and the intermetallic phase of Fe2AI5 type was observed. The morphological examination after stretching was carried out in a light microscope, high-resolution scanning electron microscope and EBSD analysis.