Papers by Keyword: Fe₃Al

Abstract: Cobalt is widely used to produce WC-Co hard metals, but this binder has problems of shortage and unstable price. In this work, cobalt was replaced by an iron aluminide intermetallic binder. WC-10%(Fe₃Al-3%B) composite was prepared by vibration milling of WC, Fe, Fe-B, and Al powders and sintered by spark plasma sintering (SPS) at 1150 °C for 8 min under 30 MPa. The milling time was 0.17, 12, 25 and 50 h. The SPS was efficient to consolidate the composite resulting in relative density of ~98% or higher. With increasing milling time, Vickers hardness (HV₃₀) of composite increased from 12 to 14 GPa due to the enhanced homogeneity of microstructure, while the fracture toughness, K_Ic, determined by an indention fracture method using Shetty equation, remained constant at around 9.1 MPa.m^1/2.

Abstract: Tungsten carbide (WC) based composites are usually produced with cobalt, but this binder has the inconvenience of shortage, unstable price and potential carcinogenicity. The objective of this study was to develop WC composite with intermetallic Fe₃Al matrix. Powders of WC, iron and aluminum, with composition WC-10 wt% Fe₃Al, and 0.5 wt% zinc stearate were milled in a vibration mill for 6 h and sintered in a SPS (spark plasma sintering) furnace at 1150 °C for 8 min under pressure of 30 MPa. Measured density and microstructure analysis showed that the composite had significant densification during the (low-temperature, short time) sintering, and X-ray diffraction analysis showed the formation of intermetallic Fe₃Al. Analysis by Vickers indentation resulted in hardness of 11.2 GPa and fracture toughness of 24.6 MPa.m^1/2, showing the feasibility of producing dense WC-Fe₃Al composite with high mechanical properties using the SPS technique.

Abstract: The iron aluminides seem to be very perspective materials for high temperature structural application. They have many advantages, but unfortunately also some negative properties – e.g. sharp drop in strength above 600°C or limited ductility at room temperature. These disadvantages can be reduced by alloying of binary alloy by other elements.Present work deals with a study of coefficient of thermal expansion (CTE). It was investigated the influence of microstructure and heat-treatment on the values of CTE. Secondary, it was studied the possibilities, how to determine phase transition temperatures from CTE curves. Influence of type of iron aluminides lattice on CTE values was also examined as well as the influence of addition of alloying elements into binary iron aluminides.

Abstract: 800x600 Intermetallics are compounds of two metals or of metal(s) and semimetal(s). Their structures are usually different from those of the constituents. Some intermetallics are interesting functional materials, others have attracted attention as high-temperature structural materials. We remind the reader of some fundamentals of solid-state diffusion and to the major techniques for tracer diffusion measurements, interdiffusion studies and the growth kinetics of layers in solid diffusion couples. Starting from self-diffusion, which is the most basic diffusion phenomenon in any solid, the paper covers the main features of diffusion in binary intermetallics from the systems Cu-Zn, Ni-Al, Fe-Al, Mg-Al, Ni-Ge, Ni-Ga, Fe-Si, Ti-Al, Ni-Mn, Mo-Si, Co-Nb and Ni-Nb.. We illustrate the influence of phase transitions on diffusion and point out some common features of diffusion in intermetallics. We discuss in detail diffusion in silicides of iron, molybdenum and of silicides of refractory metals. We also consider aluminides of iron, nickel, and titanium and in the aluminium-magnesium system. We consider diffusion in intermetallics of the cobalt-niobium and nickel-niobium system and in in the Nb-Sn and V-Ga systems. We finish with some remarks about grain boundary diffusion in intermetallics. Normal 0 21 false false false UK X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif";}

Abstract: Recycle-type Fe₃Al (hereinafter designated as Re-Fe₃Al) based alloys reinforced by the carbides of TiC or ZrC were processed by the high frequency induction melting method using a high-carbon Cr steel sludge, Al can scraps and the transition metals of Ti or Zr. The carbides were synthesized by in-situ reaction between the transition metal and carbon in the molten iron aluminum alloy. Vickers hardness values are 309HV0.5 for Re-Fe₃Al/TiC alloy, and 473HV0.5 for Re-Fe₃Al/ZrC alloy, which are higher than that of P-Fe₃Al (preprared from pure-Fe and-Al). The cutting performance of the Re-Fe₃Al baed alloys was compared with a High-Speed-Steel (HSS) by cutting tests for pure-Cu extruded bar (C1020) using a lathe under a dry condition. Tool life limit was estimated from frank wear length after the cutting tests of C1020 by finish-machining. Tool life limit of Re-Fe₃Al/TiC alloy is more than16 min; P-Fe₃Al was 12 min; HSS was 8 min, Re-Fe₃Al/ZrC alloy was 7 min at the cutting speed of 100m/min. Also, tool life limit of the Re-Fe₃Al/TiC alloy was more than twice times as long as that of the HSS at the cutting speed of 300/min. The relationship between cutting speed and tool life limit clearly indicated that the Re-Fe₃Al/TiC alloy was better than the HSS at a higher cutting speed. Therefore, it was concluded that Re-Fe₃Al/TiC alloy has excellent cutting tool performance.

Abstract: The effects on property of Fe3Al-based alloy adding 1.0at.%Mn,5at.%Cr,0.5at.%V have been studied. Alloys were smelted in a vacuum arc furnace and heat treated in box furnace under atmosphere. The tensile property test and hardness measurement indicate that Cr and V both can improve the room temperature ductility of Fe₃Al-based alloy effectively, the effect of micro V to the ductility is correspond to the effect of 5at.%Cr, the Fe3Al alloyed by V has higher tensile strength and yield strength, the effect of 1.0 at.%Mn on the property of alloy is not obvious. The effects of various elements on Fe3Al-based alloy ductility are analyzed according to the electronegativity different of between the three atoms and Fe/Al atoms. Microstructure analysis shows that the reason of V improving the strength is the effect on solution strengthening and the second phase strengthening.

Abstract: Sialon matrix composites were prepared from a reaction mixture of Si₃N₄, Al₂O₃ and Y₂O₃ powders and reinforced with Fe₃Al obtained by mechanical alloying, which also can assist sintering at a low temperature. The specimens were sintered by two–step hot pressing and then characterized for phase composition, microstructure and mechanical properties. The effect of the Fe₃Al variables on the mechanical properties was studied.

Abstract: Bulk nanocrystalline Fe₃Al based materials with 5, 10 and 15 wt. % Cu were prepared by aluminothermic reaction in which the melts were superheated about 1600 K before solidification. Microstructures of those materials were investigated by optical microscope, electron probe microanalysis, X-ray diffraction and transmission electron microscope. It was shown that microstructures of the materials consisted of a nanocrystalline matrix phase and a little contamination Al₂O₃ and Fe₃AlC_x fiber phases. The nanocrystalline matrix phase was composed of Fe, Al and Cu elements and disordered bcc which did not change with content of Cu. Average grain sizes of the nanocrystalline phase of the materials with 5, 10 and 15 wt. % Cu were 18, 24 and 25 nm respectively and that of the material with 5 wt. % Cu was the smallest. Compressive properties of the materials were tested. The material with 5 wt. % Cu has good ductility compared with the materials with 10 and 15 wt. % Cu. Yield strength of the materials was about two times higher than that of coarse grained Fe₃Al material. The compressive yield strength of the material with 5 wt. % Cu was higher than those of the materials with 10 and 15 wt. % Cu and its flow stress in compression was up to about 1500 MPa.

Abstract: The corrosion behavior of Fe₃Al was studied by high temperature autoclaves in H₂S/CO₂ environment. By Stereo Microscope, we found that the corrosion film of Fe₃Al is thin and crack at 60°C, 4.0 Mpa,after 72h in autoclaves; Phase analysis by XRD showed that the main composition of corroded products is FeS; its corrosion are Ⅲ corrosion resistant type and corrosion rating of 4, mainly pitting, and average corrosion rate of 0.2106 mm/a.

Abstract: The casting Fe₃Al intermetallics were solidified in sodium silicate sand mould and permanent mould respectively to get different cooling rates. After heat treatment (1000°С/15 h homogenizing annealing + furnace cooling followed by 600°С/1 h tempering + oil quenching), the microstructure and properties of Fe₃Al intermetallics were investigated. The results show that the heat-treated Fe₃Al intermetallics at higher cooling rate has finer grained microstructure than lower cooling rate, and the lattice distortion increases due to the higher solid solubility of the elements Cr and B at higher cooling rate. The tensile strength and hardness of the Fe₃Al intermetallics at higher cooling rate are slightly higher also. However, the impact power of intermetallics at higher cooling rate is 67.5% higher than that at lower cooling rate, and the impact fracture mode is also transformed from intercrystalline fracture at lower cooling rate to intercrystallin+transcrystalline mixed fracture at higher cooling rate.