Experimental Observation & Numerical Analysis On Kinetics Of Temperature Dependent Martensitic Transformation

Quenching technology,as with its long history of application,is the crystallization of human wisdom.Scientific research has found that the carbon steel would form a kind of brittle and hard martensite microstructure through quenching.Due to the material composition,the martensite microstructure differs in micromorphology.Excellent comprehensive mechanical properties of materials can be obtained through different means of heat treatment which combine martensite and toughness microstructure.Therefore,the research in kinetics of the martensite phase transformation carried out in this article has a guiding significance on the microstructure optimization of materials.The T10 A specimens are quenched after heated at high temperature,then tempered in different temperature,through which the tempered martensite microstructure are obtained.By means of the observation of the tempered microstructure,the performance of the martensite phase transformation in different temperature would be known.The martensite obtained at high temperature is at large size and in long needle shape,the quantity is small;with the decreasing temperature,the quantity of the martensite increases sharply,the shape turns into coarse needle from fine needle,the size is smaller as the constraint of the early martensite;at room temperature,the martensite present tiny and fine needle shape.Martensite content is measured by quantitative metallography,and the kinetics curve is drawn.The result got by area method is compared with that by particle plane-space conversion method,the trend is basically identical.A certain shape and size of martensite from the experimental observation is taken as the prototype,the martensite and parent phase three dimensional finite element models are established.Analysis of elastic contact models show that the energy consumption of the long ellipsoid needle model is too high,while the elastic potential energy of the oblate ellipsoid model is reasonable,which correspond to the martensitic morphology analysis results in the past.