ON THE EMBRITTLEMENT OF A RAPIDLY SOLIDIFIED AL-FE-V-SI ALLOY AFTER HIGH-TEMPERATURE EXPOSURE

Abstract

The effects of high-temperature exposure on the mechanical properties and the microstructure of a rapidly solidified Al-Fe-V-Si alloy were examined in order to identify the critical factors controlling the thermal stability of the alloy, particularly at temperatures above 400-degrees-C. Room-temperature (RT) tensile tests were conducted on specimens exposed to temperatures ranging from 150-degrees-C to 482-degrees-C for 100 hours. The microstructure of the extrusion is characterized by a banded structure consisting of a layer containing fine silicide dispersoids and a layer containing coarse silicide dispersoids, which is a replication of the microstructure of the melt-spun ribbon. The alloy did not show any significant change in tensile properties after 100 hours exposure up to 427-degrees-C due to the stability of the microstructure. However, after exposure above 427-degrees-C, tensile elongation decreased significantly and the brittle cleavage regions were observed on the fracture surface. The occurrence of brittle cleavage fracture is due to the presence of coarse equilibrium Al13Fe4 or Al3Fe phase, which forms by the transformation of the coarse silicide dispersoid above 427-degrees-C.