Papers by Keyword: Fe-Al

Abstract: Steel 22MnB5 is widely used in the automotive industry for manufacturing high-strength structural car body parts. To achieve desired mechanical properties, hot-stamping is used, during which the Al-Si coating plays a critical protective role against oxidation. This study investigates the structural evolution of the Al-Si coating under various austenitization durations at 920 °C. Intermetallic phase formation and coating morphology are analyzed.

Abstract: The Oxide Precipitation Hardened (OPH) steel is a new developed group of materials from Oxide Dispersion Strengthened (ODS) alloys which are well known advanced materials for high temperature properties. Besides, the corrosion resistance of these types of material is so important regarding to their practical usage. The production of OPH alloys, the same as ODS alloys, involves mechanical alloying process to create material with ductile matrix and hard oxide dispersion. Six variants of Fe-Al base OPH steel which developed and manufactured by the authors, were prepared with different chemical composition to evaluate the role of main component on the mechanical properties and corrosion resistance of new-developed OPH steels. The corrosion tests were done using potentiodynamic polarization methods. The results show that the Aluminum content has a main role both on mechanical properties and corrosion resistance.

Abstract: Recently, the use of high temperature materials are became more common in different types of engineering activities. The new generation of Oxide dispersion strengthened alloys (ODS) consist of Fe-Al matrix with small oxide particles dispersed within it, was generated by the authors to keep their mechanical properties at elevated temperatures. The new ODS prepared by means of mechanical alloying and hot consolidation. The preliminary tests results shows a better oxidation resistant, creep and Ultimate Tensile Strength (UTS) compare to similar materials. To go more inside in thermomechanical and microstructural properties, a series of different test were performed on different variant of ODS which manufactured by the authors. The results show that the annealing time and temperature has a significant influence on these properties while almost total recrystallization of grains and subgrains were observed during the investigation.

Abstract: Nowadays, by increase in using structural materials, the high temperature properties of these materials are became an important issue within different aspects of engineering. The new Oxide Precipitation Hardened (OPH) steel generated by the authors based on Fe-Al-O matrix which prepared by mechanical alloying and hot consolidation. These new OPH steels showed a better oxidation resistant and creep, compare to similar ones. In order to investigate the thermomechanical and microstructure of these materials, a series of different tests were performed on three different OPH steels variant which developed and manufactured by the authors. The results show that the heating temperature has a significant influence on these properties while almost total recrystallization of grains and subgrains were observed during the investigation.

Abstract: It is well known that intermetallic compound alloys possibly include more than two types of vacancies basically, that is A-vacancy and B-vacancy in A-B compound alloy. Although MeV ordered electron irradiation produces vacancies and interstitials, the threshold energy of displacement for each elemental atom in intermetallic alloys is not necessarily same. Then the defect type introduced by the irradiation depends on electron energy. In this study, we performed positron annihilation lifetime and Doppler broadening measurements for different energy of electron irradiated B2 type Fe50%Al alloy. The values of positron annihilation lifetime for this alloy after 2 and 9 MeV electron irradiation were 200 and 172 psec, respectively. Also, the Doppler broadening parameters S and W show difference for this alloy with different energy of electron irradiation. These results suggest that different types of vacancy were induced into Fe-Al compound alloy by electron irradiation with different energies.

Abstract: The structure, point defect and ordering parameter of Fe25Al samples is examined with the Mössbauer spectroscopy Positron Annihilation Lifetime Spectroscopy XRD and SEM. The studies are carried out for samples in as-cast state and after heat treatments: annealing for 24 hours at 900°C (or 1050°C) and either slow cooling with furnace or quenching to oil. Among the research method used, Mössbauer spectroscopy for determination of hyperfine structure parameters was adopted. These parameters, sensitive to changes in spin and charge electron densities in the nearest neighbourhood of a Mössbauer isotope nucleus, caused by specific configurations of atoms, are directly connected with the degree of ordering of a compound. Spectral analysis has been carried out using an authors’ software developed based on a theoretical model relating the shape of a Mössbauer spectrum to the sample microstructure. It has been shown that Mössbauer spectroscopy enables quantitative evaluation of the degree of ordering of phases occurring in samples characterised by large graining, in the case of which it is not possible to determine the long-range order parameter by X-ray diffraction. The PALS method only one type of defects is detected. The positron lifetime in these defects (V) suggests that they are quenched-in Fe-monovacancies (VFe). The vacancy concentration strongly depends on the rate of cooling.

Abstract: In this work, the Mössbauer spectroscopy employed in a study of point defect formation in intermetallic phases of the B2 structure from the Fe-Al system as a function of Al concentration. We present the values of the 57Fe isomer shift and quadruple splitting for the components describing the point defect in the local environment of a Mössbauer nuclide. The concentration of the Fe vacancies and Fe atoms substituting Al (Fe-AS) are determined. The results shown that an increase in Al content causes an increase in vacancy and Fe-AS concentration.

Abstract: Fe-28Al and Fe-28Al-10Ti alloys were prepared by mechanical alloying and hot pressing. The phases and dry sliding wear behavior were studied. The results show that Fe-28Al bulk materials are mainly characterized by the low ordered B2 Fe₃Al structure with some dispersed Al₂O₃ particles. Fe-28Al-10Ti exhibits more excellent wear resistance than Fe-28Al, especially after long distance sliding wear test. There are obvious differences in wear mechanisms of Fe-28Al and Fe-28Al-10Ti alloys under different testing conditions. Under the load of 100N, there is plastic deformation on the worn surface of Fe-28Al. The main wear performance of Fe-28Al-10Ti is particle abrasion, the characteristics of which are micro cutting and micro furrows, but micro-crack and layer splitting begin to form on the surface of Fe-28Al. Under the load of 200N, serious plastic deformation and work-hardening lead to rapid crack propagation and eventually the fatigue fracture of Fe-28Al. Plastic deformation is the main wear mechanism of Fe-28Al-10Ti under the load of 200N, which are characterized by micro-crack and small splitting from the worn surface.

Abstract: Fe-28Al and Fe-28Al-10Ti alloys were prepared by mechanical alloying and hot pressed sintering. The mechanical properties and wear resistance were studied. The results show that Fe-28Al bulk material is mainly characterized by the low ordered B2 Fe₃Al structure with some dispersed Al₂O₃ particles. The mechanical properties such as the hardness and strength of Fe-28Al-10Ti are significantly improved compared with Fe-28Al, which is attributed to the grain refinement and solid solution reinforcing with the addition of Ti element. The fracture mode is mainly the intergranular fracture. Fe-28Al-10Ti exhibits more excellent wear resistance than Fe-28Al, especially after long distance sliding wear test. There is difference in wear mechanisms of Fe-28Al and Fe-28Al-10Ti alloys. Under the load of 100N, there is obvious plastic deformation on the worn surface of Fe-28Al. Micro-crack and layer splitting occur on the surface of Fe-28Al. The main wear performance of Fe-28Al-10Ti is particle abrasion, the characteristics of which are micro cutting and micro furrows.

Abstract: The defect structure of Fe28Al samples is examined with the Positron Annihilation Lifetime Spectroscopy. The studies are carried out for samples in as-cast state and after heat treatments: annealing for 24 hours at 900°C (or 1050°C) and either slow cooling with furnace or quenching to oil. The PALS spectra are analyzed using two-state trapping model. Only one type of defects is detected. The positron lifetime in these defects (V) suggests that they are quenched-in Fe-monovacancies (VFe). The vacancy concentration strongly depends on the rate of cooling. Besides, V also depends slightly on the rate of cooling of the material. This fact suggests, according to the predictions of latest theoretical calculations, that V is sensitive to the atomic configuration in the nearest neighborhood of VFe, which give hope to estimate the degree of atomic ordering in alloys by the PALS technique.