Estudo da fundição em aluminetos de ferro.

Abstract

Iron aluminides are good candidates for applications at moderate to high temperatures (up to 500 °C) because they combine excellent oxidation resistance with good mechanical properties. However, these materials have low ductility at room temperature (less than 5% traction elongation), a characteristic correlated to environmental effects, which hinders their conformation process. Casting is a processing route traditionally applied to brittle alloys (eg, gray cast iron), it is necessary to know the thermochemical properties of the alloys to reduce the formation of defects attributed to the casting process, such as the formation of pores, scar and blows. In this work, three different alloys of intermetallic (Fe28Al, Fe28Al6Cr and Fe28Al6Cr1Ti) were investigated under the influence of different solidification conditions.For these three alloy compositions, grain size reduction by up to 60% was observed by the addition of Al-5Ti-1B as an inoculant to the molten metal. The alloys were produced under laboratory conditions (induction furnace with a maximum capacity of 2 kg and protection under Air flow), as well as industrial scale (induction furnace with capacity of 100 kg). The industrial scale process resulted in castings with a small number of defects, which is an indication of the ability to produce mechanical parts of these iron aluminides directly by the casting process. The X-ray tomography technique assisted in the measurement of linear contraction (~ 6%) and tendency to defect formation. In addition to the microstructural characterization of the alloys, this work includes a discussion about the reactivity of the molten metal and the refractory material coating the induction furnace. In this way, the obtained data allow to investigate the FeAl alloys castability by the use of induction furnace.

Avaliando o papel do dano na mecânica de segmentação de cavacos.

“…Fe28Al6Cr1Ti) with increasing inoculant content (0.0%, 0.05% and 0.10%). Source: adapted from [126] scales which are not found in industrial scale melts. Whilst large scale presence of κ-carbides can affect properties related to machining, there is no evidence that low concentration of hard second phases can affect machining performance.…”

“…With castings, inoculants are normally used in order to reduce the final grain size of the casting. Ramirez [126] applied a Al-5Ti-B inoculant successfully, reducing in 60% the final grain size of the casting. Grain size and shape, as reported in [121], hinders hydrogen embrittlement evolution.…”

“…Cast iron aluminides were produced by Ramirez [126], the alloys were presented in Figure 24. For this particular work, the alloys selected for the work were Fe28Al (alloy A) and Fe28Al6Cr1Ti (alloy B), bothwith no inoculant.…”

“…In the work of Ramirez [126], TiN coated tools proved to be a very difficult and challenging task, as tools presented a high level of flank wear across all cutting speeds and feeds. The hypothesis is that there is great amount of diffusional interaction Figure 30 presents the cutting tool geometry used for the cutting forces measurement.…”

“…For chip mounting, metal clips were used to set the chip on its side for inspection of the transverse longitudinal section. The etchant used for metallographic feature inspection was 25 mL acetic acid, 15 mL HNO 3 , 15 mL HCl and 5 mL H 2 O for 10 seconds [126], this etchant reveals grain boundaries but also deformation shear bands in Fe 3 Al.…”