Vesna Maksimović

FAILURE ANALYSIS OF JET ENGINE TURBINE BLADE

Jet engine turbine blade cast by investment precision casting of Ni-base superalloy, which failed during exploatation, was the subject of investigation. Failure analysis was executed applying optical microscopy (OM), transmission electron microscopy (TEM) using replica technique, scaning electron microscopy (SEM) and stress rupture life tests. On the ground of obtained results it was concluded that the failure occurred as a result of structural changes caused by turbine blade overheating above the exploitation temperature.

Aging of a Commercial Al-Cu-Si Based Alloy Modified with Germanium

The effect of small addition (0,7 wt.%) of Ge on precipitation during aging at 190oC of a modified commercial Al-Cu-Si based alloy has been studied. It was found that the maximum hardness in the alloy containing Ge was achieved three times faster than in the alloy without Ge. TEM results clearly demonstrate that the accelerated precipitation should be ascribed to a dense and fine distribution of Si-Ge particles serving as sites for heterogeneous precipitation of and phases. Accelerated precipitation during aging was accompanied by increase in hardness.