Abstract Maraging steels are among the highest strength steels commercially available. Despite being relatively rare and expensive, they may present a yield strength around 3 GPa and are indispensable for various applications. In the present paper, several aspects will be reviewed related to maraging steels including a brief history of its development, microstructure and acting hardening mechanisms, loss of toughness with the tensile strength increase, resistance to oxidation, and corrosion, nitriding behavior, and future perspectives.

Abstract Initially studied was the effect of the casting mode on the electrical conductivity of AA4006 aluminum alloy sheets produced by both Twin Roll Casting (TRC) and by the semi-continuous Direct Chill (DC) industrial processes, when compared to sheets with commercial purity (AA1050) and high purity aluminum (AA1199). Then, the effects of heat treatments on the electrical conductivity of the AA4006 alloy sheets produced by TRC were also studied. Isochronous and isothermal heat treatments allowed to obtain the precipitation and solution kinetics of the intermetallic compounds. The precipitation kinetics was analyzed with the help of the Johnson-Mehl-Avrami-Kolmogorov equation.

The influences of the chemical composition and heating rate have been studied in 300 and 350 maraging steels using dilatometry. For these tests, heating was carried out with heating rates of 1, 10 and 28 °C/s. The results have shown that the precipitation mechanism for both materials in the studied range is by lattice diffusion. Furthermore, Co and Ti contents influence strongly the precipitation. The lattice diffusion mechanism in the martensite reversion is influenced by Ni and Co contents and heating rate. For small heating rates ( ~1 °C/s) this mechanism prevails in the 300 maraging steel while for the 350 maraging steel has a minor importance. The mechanism of martensite reversion for 350 maraging steel in the studied range is mainly by shear mechanism. For higher heating rates (~28 ºC/s) the shear mechanism prevails in both maraging steels.