Transformation-induced plasticity in rapidly solidified Fe88.9Cr4.3V2.2C4.6

In the present work, the mechanical behaviour at different strain rates of a high strength tool steel with the composition Fe88.9Cr4.3V2.2C4.6 (at.%), manufactured under relatively high cooling rates and highly pure conditions, was studied. The applied preparation conditions promote a microstructure composed of martensite, retained austenite and a fine network of special carbides already in the as-cast state. This special phase combination yields a structural material with superior mechanical properties under quasi-static loading, exhibiting an extremely high engineering compression strength of almost 4000 MPa combined with a large compression strain of about 20% due to deformation-induced martensite formation. However, the knowledge of the performance of this material under dynamic loading conditions is also very important for its possible application as a novel kind of tool steel. For this reason, compression tests in the strain rate range of 10(-3)-10(3) s(-1) were performed and the transformation-induced plasticity (TRIP effect) was investigated. The analysis of the transformation behaviour of the retained austenite reveals that the rate of martensite formation decreases with increasing strain rate. Furthermore, an increase of the offset yield stress and the compression strength with increasing strain rate together with a remarkable plasticity was detected.