Improvement of Mechanical Properties of 20CrMnTi Steel through Microstructure Modification

Microstructure modification is an effective approach to improve the mechanical properties of materials. In the present study, expanded graphite (EG) was added in a 20CrMnTi matrix to form pearlite microstructure and proeutectoid cementite after sintering. Mechanical alloying was used to obtain a fine milled mixture with a ball/powder weight ratio of 20:1. After mechanical alloying for 10 h, the milled mixtures with different EG contents were pressurelessly sintered at 1250 °C for 10 min and then hot-pressed at 1150 °C under 30 MPa for 30 min in Ar to obtain dense and modified 20CrMnTi materials. The content of EG has a profound influence on the microstructure and mechanical properties of 20CrMnTi. A high tensile strength of 1088 MPa and a high Vickers hardness of 4.7 GPa were achieved in the 1% EG-modified 20CrMnTi, which were increased by 105% and 28%, respectively, compared with the pure dense 20CrMnTi. The formed fine pearlite and small proeutectoid cementite in the modified microstructure contributed to the improved mechanical properties of 20CrMnTi.