Fabrication of composite graded materials based on Fe-Al phases
Tomasz Durejko, Stanisław Lipiński
Quarterly No. 3, 2009 pages 297-301
DOI:
keywords: powder metallurgy, Fe-Al intermetallic phases, Fe-Al composite graded materials
abstract According to data published in subject literature, we have concluded that, application of Fe-Al intermetallic phases in graded system could be an interesting and innovative solution. Actually, only Fe3Al and FeAl phases have found some application, due to their excellent corrosion resistance and high-temperature structural stability. Other phases - Fe2Al5 and FeAl2, with high aluminium content, are extremely brittle and can’t be widely used. In spite of this, it’s supposed that application of that phases in graded systems improve their properties, because proper arrangement of hard high-aluminium phases could increase abrasive resistance of entire material. Results of our previous research indicate that both mechanical strength and structural stability of Fe-Al intermetallic phases are higher comparing to conventional materials and some superalloys. Proposed graded systems should fulfill requirements for high-temperature material. Manufacturing of Fe-Al continuous and non-continuous (chemical composition and particle size of powders) composite graded materials was presented in this paper. The gradient effect was obtained by two methods - ultrasonic and layered filling of matrix. The layered filing was fabricated by using numerical controllable head charge (own construction). The used device made possible fabrication of chemical continuous Fe-Al graded material. After matrix filling process the powders mixture was cold pressed and presintered at 620°C. The structure of obtained samples was examined by microscopy observation and chemical analysis. It was stated that ultrasonic method made possible only local gradient effect. This method can be used for early segregated (particles size) powder charge in order to powder particles mixed on boundary between layers. The matrix filling method made possible gradient effect in all compact volume. Depending on delivery of powders from charge head feeder was obtained continuous or non-continuous gradient effect. Additionally for non-continuous graded material was determined thickness of powder layer vs. charge head feed in XY working plane. It was taken that after preliminary heat treatment of compacts gradient effect remained. There are iron and high aluminium intermetallic phases with dispersion Al2O3 oxide distributed along grain boundaries observed.