Microstructure and Properties of Rapid Heat Treated Galvanized Dual Phase Steels

In order to improve fuel efficiency and reduce greenhouse emissions, the automotive industry has to use more and more advanced high strength steels. Indeed, these steels benefit from both good formability and high-energy absorption capacity, and enable manufacturers to reduce the mass of vehicles. To achieve this requirement, refining the non-ferritic phase in steel is a proposed solution. Specifically rapid heat treatment can change the scale and the distribution of the second phase, ameliorating the mechanical properties. However, such heat treated steels, before being used, have to be galvanized to avoid corrosion and maintain the material’s mechanical properties. This study aims to determine the mechanical properties and the galvanisability of steels processed by rapid heat treatment. Accordingly, samples were galvanized following designed rapid heat treatment routes. It has been shown that, the thermal cycles influenced the mechanical properties of the Dual Phase steels through the volume fraction and the distribution of martensite. In addition, the thermal treatments did not affect the formation of the inhibition layer nor the quality of the zinc coating, and this in spite of the presence of a Mn oxide layer at the steel surface during heating.