Volume 49, Issue 9

In order to get small-dimensioned shape memory alloys (SMAs) with good functional and mechanical properties, a rapid solidification technique was employed. This paper discusses the use of different melt-spinning procedures for the preparation of proper thin NiTi ribbons. Metallographic characterization of SMAs is an important way to evaluate material properties, therefore the effect of alloy composition and different conditions of melt-spinning process (crucible, melting time and temperature) on the various inclusions and microstructure of NiTi alloys was investigated. Specimens for metallographic studies were cut from the longitudinal cross sections of melt-spun ribbons. The microstructures and different phases were examined by optical, scanning and transmission electron microscopy and the influence of the processing methods on microstructures of ribbons will be discussed.

The paper discusses employing a variety of microscopical techniques and their limitations in the context of the evaluation of the area fraction of structural components. The idea of the joint application of several types of microscopes to area fraction assessment depending on the sizes of objects being evaluated is introduced. The relevant measuring schemes and formulae for the correct calculation of the total area fraction in two, three, four or five stage analyses using light and electron microscope techniques are presented together with practical examples and results. In this joint approach the advantages of each microscope type are utilized while avoiding the drawbacks. A concept of the local area fraction is suggested and applied in the quantitative evaluation of a carbide phase in an economical niobium high-speed steel. The appropriate variants of the joint method are recommended for various size scales and size distributions of objects to be analyzed. The methods described enable an accurate evaluation of area fraction in cases where the possibilities of single microscope techniques are insufficient.