INFLUENCE OF THE SHAPE OF HYDROGEN-CONTAINING INCLUSIONS ON THE INTERGRANULAR CORROSION PROCESS OF THE AL - SI ALLOY SYSTEM

Abstract

It is known that the surface of aluminum alloys is characterized by the formation of pitting (point damage), which can subsequently cause intergranular corrosion. This corrosion damage is dangerous in that it is almost impossible to detect it visually, since it extends from surface into interior of the material. The effect of the form of hydrogen inclusions on the corrosion resistance of an Al – Si alloy is investigated. For the tests on intergranular corrosion were selected uncoated samples of silumin AK12 (ENAC-AlSi12(a), A04130) with different forms of hydrogen inclusions — atomic and molecular. The content of dissolved hydrogen in all samples is 0.2 cm3/100 g. The duration of methodical tests in special solution of sodium chloride (NaCl) and hydrochloric acid (HCl) is 24 hours. Additionally, two samples from each series were exposed to a solution of another 48 hours. Evaluation of the effects of intergranular corrosion on silumin samples was performed by metallographic method. Given the fact that the data on the loss of mass over a certain period of time are less reliable, in comparison with the data on the structure change over the same time. Then, the effect of intergranular corrosion on the mechanical properties of silumin was evaluated using the electromechanical universal testing machine. During the research was found that at the equal content of the dissolved hydrogen samples with molecular inclusions are more subject to intergranular destruction. This follows from the considerable depth of corrosion propagation and the decrease in the mechanical properties of silumin relative to the results for samples with atomic hydrogen. Wherein the analysis of the level of mechanical properties showed that after intergranular corrosion, the tensile strain decreases to a considerable extent. The work was carried out within the project 14.578.21.0193 “Development of theoretical and technological solutions for hydrogen reduction in aluminum and lowalloyed aluminum alloys” of the Federal Target Program “Researches and developments in the priority directions of progress of Scientific and Technological Complex of Russia for 2014–2020” with the financial support of the Ministry of Education and Science of the Russian Federation. The unique identifier of agreement RFMEFI57816X0193.