Structure and properties of closed-die forged Fe-Al powder layer composites
Stefan Szczepanik, Marek Wojtaszek Akademia Górniczo-Hutnicza, Wydział Inżynierii Metali i Informatyki Przemysłowej, al. Mickiewicza 30, 30-059 Kraków, Poland
Quarterly No. 4, 2008 pages 317-321
DOI:
keywords: powder metallurgy, consolidation, structure, mechanical properties, fracture, layer composite
abstract To obtain alloys with intermetallic phases metallurgical processes and PM routes are used. The research focuses mainly on the materials obtained in the metallurgic route. The main disadvantage of the alloys based on Fe-Al phases is their low plasticity at room temperature and low strength at elevated temperatures. The aim of the research in this paper is to determine the influence of hot deformation and heat treatment of the preforms obtained from a mixture of iron and aluminium powders as well as the influence of the multilayer geometry of hot consolidated layer composite samples on the density and mechanical properties of these materials. The paper presents the results of the research of Fe-Al materials after hot consolidation of the Fe-Al PM performs. Fe-Al PM Fe-Al [30 and 40 wt. %] PM layer performs were cold pressed and consolidated by hot closed-die forging at 480oC to yield high-density composites. Microstructures and mechanical properties were studied after consolidation, and also after 4 h heat treatment at 550oC. After consolidation hardness of the base materials was in the range 25÷43 HB, after heat treatment 25÷62 HB, and bend strengths then in the range 83÷91 MPa. Fe-Al phases on the boundary surfaces of the specimens had microhardness HV0.02 of 1240. Bend strengths of composite samples were in the range 90÷105 MPa, depending on chemical composition and layer geometry of the specimens. The plasticities of Fe-Al composites were smaller than of the starting metals. Fractographs of bend specimens show regions of brittle in area reach in iron and Fe-Al phases, and ductile failure in aluminium - rich regions. These data can contribute to design of layer materials for specific applications utilising the PM route and closed-die forging.