Effect of Cu Alloying on Mechanical Properties of Medium-C Steel after Long-Time Tempering at 500 °C

• Published in: Materials Vol. 16; no. 6; p. 2390
• Main Authors: Salvetr, Pavel, Gokhman, Aleksandr, Svoboda, Milan, Donik, Črtomir, Podstranská, Ivana, Kotous, Jakub, Nový, Zbyšek
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 16.03.2023; MDPI
• Subjects: Alloy steels; Alloying; Carbon; Carbon steel; Charpy impact test; Copper; Copper alloys; Copper base alloys; Cu precipitate; Dislocation density; Elongation; Grain boundaries; Grain size; Hardness; Heat treating; Impact strength; Impact tests; long-time tempering; Martensite; Mechanical properties; Medium carbon steels; medium-C steel; Microstructure; Precipitates; Precipitation hardening; Quenching and tempering; Reduction of area; Solid solutions; Specialty metals industry; Steel; Strengthening; Temperature; Tempering; Tensile strength; Yield stress; Denmark; Japan; long-time tempering; strengthening; medium-C steel; Cu precipitate; mechanical properties
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma16062390

This research studies the influence of the copper alloying of medium-carbon steel on mechanical properties after quenching and tempering at 500 °C. The microstructure was characterised using SEM, EBSD, TEM, and XRD analysis. The mechanical properties were comprehensively investigated using hardness measurements, tensile and Charpy impact tests and solid solution, grain boundary, dislocation, and precipitation strengthening contributions were estimated. Higher yield strength for Cu-alloyed steel was confirmed at about 35-73 MPa. The precipitation strengthening contribution from Cu precipitates in the range of 11-49 MPa was calculated. The interaction between Cu precipitates and dislocations retards the decrease in dislocation density. Similar values of effective grain size of martensite crystals were measured for Cu-alloyed and Cu-free steel as well. Copper alloyed steel exhibited significantly deteriorated impact toughness, total plastic elongation, and reduction of area. The size of Cu precipitates ranged from 8.3 nm after tempering at 500 °C for 6 h to 13.9 nm after tempering for 48 h.