INFLUENCE OF Al AND Mn IMPURITIES ON STRUCTURAL PROCESSESTRANSFORMATIONS IN COPPER ALLOYS

Abstract

In the work on specific examples involving real copper-based
alloys containing 14 weight.%Al and 3 weight.%Mn, describes the results of a
study of the process of restoring the shape of a material that was defomated
according to the three-point bending scheme. The studies were carried out by
measuring changes in the temperature dependence of the electrical resistance and
deflection of the sample, as well as by obtaining microelectronograms using an
electron microscope. Since SME alloys operate under conditions of mandatory
thermal cycling, the elucidation of the thermal stability of these materials is of
practical interest. It is established that martensitic crystals that occur in hardened
samples have a high density of packing defects and thin twins formed on the
(121) γ´ plane. One of the important features of the martensitic mechanism is the
obligatory formation of martensite with defects, which is a fine structure. By
comparing the curves of the electrical resistivity and the deflection, it was found
that the temperature range of the increase in the deflection upon cooling
coincides with the temperature range of the direct martensitic transformation. In
addition to stacking faults, thin twins with a thickness of 0.01-0.04 microns are
also observed in martensite crystals. It was found in the analysis that twinning
in martensite occurs along the {121} γ´ plane. It is shown that the streakiness arising during martensitic transformations is caused by stacking faults, which lie
in the {121} plane at a high density of stacking faults.