• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2002.11a
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• pp.13-14
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• 2002

• Journal of the Korean Society for Heat Treatment
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• v.22 no.3
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• pp.149-154
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• 2009

Dense $5Cu_{0.6}Fe_{0.4}-Al_2O_3$ composite was consolidated from mechanically synthesized powders by pulsed current activated sintering method within 1 min. $5Cu_{0.6}Fe_{0.4}-Al_2O_3$ powder was synthesized from 3CuO and 2FeAI using the high energy ball milling. Dense $5Cu_{0.6}Fe_{0.4}-Al_2O_3$ with relative density of up to 95% was produced under simultaneous application of a 80 MPa pressure and the pulsed current. Mechanical properties and grain size of the composite were investigated.

• Journal of Powder Materials
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• v.11 no.6 s.47
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• pp.486-492
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• 2004

We report the crystallization and magnetic properties of non-equilibrium $Al_{0.6}(Fe_{x}Cu_{1-x})_{0.4}(x=0.25, 0.50, 0.75)$ alloy powders produced by rod-milling as well as by new chemical leaching. X-ray diffractometry, transmission electron microscopy, differential scanning calorimetry and vibrating sample magnetometry were used to characterize the as-milled and leached specimens. After 400 h or 500 h milling, only the broad peaks of nano bcc crystalline phases were detected in the XRD patterns. The crystallite size, the peak and the crystallization temperatures increased with increasing Fe. After being annealed at $600{^\circ}C$ for 1 h for as-milled alloy powders, the peaks of bcc $AlCu_{4}\;and\;Al_{13}Cu_{4}Fe_{3}\;for\;x=0.25,\;bcc\;AlCu_{4}\;and\;Al_{5}Fe_{2}\;for\;x=0.50,\;and\;Al_{5}Fe_{2},\;and\;Al_{0.5}Fe_{0.5}\;for\;x=0.75$ are observed. After being annealed at $500{^\circ}\;and\;600{^\circ}C$for 1 h for leached specimens, these non-equi-librium phases transformed into fcc Cu and $CuFe_{2}O_{4}$phases for the x=0.25 specimen, and into bcc ${\alpha}-Fe,\;fcc\;Cu,\;and\;CuFe_{2}O_{4}$ phases for both the x=0.50 and the x=0.75 specimens. The saturation magnetization decreased with increasing milling time for $Al_{0.6}(Fe_{x}Cu_{1-x})_{0.4}$ alloy powders. On cooling the leached specimens from $800{\~}850^{\circ}C$,\;the magnetization first sharply increase at about $491.4{\circ}C,\;745{\circ}C,\;and\;750.0{\circ}C$ for x=0.25, x=0.50, and x=0.75 specimens, repectively.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2004.04a
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• pp.36-37
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• 2004

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1999.04a
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• pp.26-27
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• 1999

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1997.04a
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• pp.26-27
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• 1997

• Journal of Welding and Joining
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• v.14 no.4
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• pp.53-61
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• 1996

It was attempted to improve the wear resistance of Al alloy under the load condition by making a formation of the thicker surface hardening alloy layers. The thicker surface hardening alloy layers were formed on 6061 Al alloys overlayed by MIG and TIG welding process with Cu powders feeding. The characteristics of hardening and wear resistance have been investigated in relation to the microstructures of alloyed layers, with a selection of optimum alloying conditions for formation of overlaying layer. The results obtained were summarized as follows With increasing feeding rate of Cu powders by MIG welding, the hardness and specific wear of the overlay weld alloys were increased. It is considered that these high hardness and specific wear of overlay weld alloys were due to the formation of Θ($Al_2Cu$) phases. With increasing feeding rate of Cu powders by TIG welding, the hardness and specific wear of the overlay weld alloys were increased in feeding rates 12 and 18g/min. However, the hardness and specific wear were decreased in the powder feeding rate 38g/min. It is considered that considered that decrease of hardness and specific wear in the powder feeding rate 38g/min due to formation of ${\gamma}$($Al_4Cu_9$) phases.

• Journal of Powder Materials
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• v.23 no.6
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• pp.432-436
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• 2016

We investigate the microstructural and magnetic property changes of $DyH_2$, $Cu+DyH_2$, and $Al+DyH_2$ diffusion-treated NdFeB sintered magnets with the post annealing (PA) temperature. The coercivity of all the diffusion-treated magnets increases with increasing heat treatment temperature except at $910^{\circ}C$, where it decreases slightly. Moreover, at $880^{\circ}C$, the coercivity increases by 3.8 kOe in Cu and 4.7 kOe in Al-mixed $DyH_2$-coated magnets, whereas this increase is relatively low (3.0 kOe) in the magnet coated with only $DyH_2$. Both Cu and Al have an almost similar effect on the coercivity improvement, particularly over the heat treatment temperature range of $790-880^{\circ}C$. The diffusivity and diffusion depth of Dy increases in those magnets that are treated with Cu or Al-mixed $DyH_2$, mainly because of the comparatively easy diffusion path provided by Cu and Al owing to their solubility in the Nd-rich grain boundary phase. The formation of a highly anisotropic $(Nd,\;Dy)_2Fe_{14}B$ phase layer, which acts as the shell in the core-shell-type structure so as to prevent the reverse domain movement, is the cause of enhanced coercivity of diffusion-treated Nd-Fe-B magnets.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.4
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• pp.172-177
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• 2002

The CuZnAl alloys have some advantages against other shape memory alloys, such as the widely variable transformation temperature, the low cost and easy fabrication. The alloys have been produced mostly by metallurgical methods. Thereby a tendency to large grain sizes is observed, which causes brittle properties of the materials. In order to avoid these deficiencies a special powder metallurgical process, SPS(spark plasma sintering), is applied in the present investigation. The starting materials were the pure (99.9 %) Cu, Zn and Al element powders with different particle size. The relatively fine grained and homogeneous Cu-24.78Zn-9.11Al (at.%) and Cu-13.22Zn-17.24Al (at.%) shape memory alloys were obtained using the powders with size of 75-150 $\mu$m. The average grain size is about 70 $\mu$m and the phases at room temperature are the austenitic and martensitic phase respectively.

• Korean Journal of Materials Research
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• v.21 no.1
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• pp.67-71
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• 2011

La doped CuO-ZnO-$Al_2O_3$ powders are prepared by sol-gel method with aluminum isopropoxide and primary distilled water as precursor and solvent. In this synthesized process, the obtained metal oxides caused the precursor such as copper (II) nitrate hydrate and zinc (II) nitrate hexahydrate were added. To improve the surface areas of La doped CuO-ZnO-$Al_2O_3$ powder, sorbitan (z)-mono-9-octadecenoate (Span 80) was added. The synthesized powder was calcined at various temperatures. The dopant was found to affect the surface area and particle size of the mixed oxide, in conjunction with the calcined temperature. The structural analysis and textual properties of the synthesized powder were measured with an X-ray Diffractometer (XRD), a Field-Emission Scanning Electron Microscope (FE-SEM), Bruner-Emmett-Teller surface analysis (BET), Thermogravimetry-Differential Thermal analysis (TG/DTA), $^{27}Al$ solid state Nuclear Magnetic Resonance (NMR) and transform infrared microspectroscopy (FT-IR). An increase of surface area with Span 80 was observed on La doped CuO-ZnO-$Al_2O_3$ powders from $25m^2$/g to $41m^2$/g.