Abstract
In this study, the ductile cast irons were prepared by the melting process and then carried out the quenching and partitioning heat treatment. The microstructures were observed by both an optical microscopy and a field emission scanning electron microscope and the tensile strengths were measured by a uniaxial tensile tester. The effect of partitioning time on the microstructures and the tensile strength were investigated. The results showed that the matrix of as-cast samples contain about 26% ferrite and 74% pearlite and the microstructure quenched without partitioning consisted of a mixture of graphite nodules plus lath martensite plus retained austenite. With the increase of the partitioning time, the retained austenite became stable and could transform into lower bainite or carbide gradually, which gave rise to the fact that the tensile strength changed nonlinearly and reached a maximum at the partitioning time about 120 minutes.
Highlights
Because of its good casting performance, low fabrication cost, excellent mechanical properties, superior corrosion resistance and abrasive resistance [1,2,3,4], ductile cast irons (DCIs) are widely used in most areas such as auto industry, mining industry, wind turbine generator, and so on [5,6]
It is well known that the excellent properties of DCIs are determined by its microstructure which consists of a steel-like matrix and graphite nodules embedded in steel-like matrix [7,8]
The quenching and partitioning heat treatment was applied to the ductile cast irons and the effect of the partitioning time on the microstructure and mechanical properties were investigated in details
Summary
Because of its good casting performance, low fabrication cost, excellent mechanical properties, superior corrosion resistance and abrasive resistance [1,2,3,4], ductile cast irons (DCIs) are widely used in most areas such as auto industry, mining industry, wind turbine generator, and so on [5,6]. It is well known that the excellent properties of DCIs are determined by its microstructure which consists of a steel-like matrix and graphite nodules embedded in steel-like matrix [7,8]. Since the matrix of DCIs has similar chemical composition and microstructure to the steels, some methods of heat treatment methods used in the steels can be used in DCIs to change its matrix microstructure and its properties. Among them, quenching and partitioning process is an important heat treatment method for steel and has already been discussed in details [15]. Howeverso far there are only few reports on the use of quenching and partitioning method to the DCIs. As a result, there are still some puzzles for DCIs under the quenching and partitioning process. The major contribution by applying this route is to develop a class of heat-treated DCIs, which can be a technological alternative in application of DCIs
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