LOW TEMPERATURE STRUCTURE OF SOME METALS AND ALLOYS

Vasile-Marius BĂRĂIAN, George ARGHIR

Abstract


Experimental research reveals that most metallic materials generally show in the range of low temperatures (+15 ... -153 oC) the reduction of the vibration amplitude of the nodes of the crystalline lattice, a fact reflected in the X-ray diffractograms; the bottom is reduced and the picks are taller and narrower. The parameter of the crystal lattice decreases with the decrease of the temperature, the density increases,
the elementary volume of the crystal lattice decreases. As the temperature decreases, phase transformations take place in special steels by transforming the residual austenite into martensite. The same phenomena occur in lead and tin: the crystallographic parameter decreases, the coefficient of thermal expansion shows
a jump, the density increases, the volume of the elementary cell decreases with the decrease of the temperature. The transformation of white into gray tin is not noticeable.


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References


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