Microalloying in Sintered Steels by Mechanical Alloying: Influence of the Alloying Elements Nature on the Grain Size Control and Properties of the Steel

摘要

Microalloyed steels have an extraordinary balance of properties thanks to the grain size control of their microstructure. In order to transfer some of these benefits to sintered steels, microalloying was performed by mechanical alloying and pressure assisted sintering. This work studies the influence of the nature of the reinforcement through all the stages of production (milling, thermal stability and sintering). For this purpose, four different compositions were prepared by mechanical milling (Fe+C (reference); Fe+0.6Nb%+C; Fe+0.6%NbC+C; Fe+0.3%Nb+0.3%NbC+C). The evolution of the starting powders with milling time was monitored by apparent and tap density, grain size distribution, DRX (crystallite size and internal strain) and SEM. The thermal stability of the resulting nanostructured powders was analyzed by DRX (crystallite size and internal strain) after annealing the powders at different temperatures (from 100°C to 600°C). To study the influence in grain size control and properties, samples were sintered by pressure assisted sintering (SPS). The sintered materials were characterized in terms of microstructure (LOM) and hardness.