A composite coating was prepared on an AZ91D magnesium alloy; first, a chromium-free potassium permanganate conversion substrate was deposited and then the substrate was further coated with epoxy resins. The surface morphology, chemical composition and deposited products of the conversion coating were investigated with scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results show that the conversion coating mainly consists of MnO2 and Al2O3 oxides, whose Pilling-Bedworth ratios (PBR) are larger than 1, indicating that the conversion coating is dense. Electrochemical-impedance-spectroscopy (EIS) plots reveal that the conversion coating shows a strong resistance to the flow of ions and electrons, demonstrating that the corrosion resistance of the AZ91D magnesium alloy is considerably enhanced. Neutral salt spray tests show that the corrosion resistance of the AZ91D magnesium alloy is substantially improved due to a composite coating consisting of a conversion deposit and an organic coating.

The Cu-37.4w/%Pb (Cu-Pb) monotectic alloys were prepared under the normal solidification conditions and intense-pulse/ electromagnetic-compound fields. The Cu-Pb monotectic alloy prepared under the normal solidification conditions was mainly composed of a-Cu and severely segregated Pb. With the compound fields applied, the segregation in the Cu-Pb alloy fabrication process could be eliminated. The alloy was composed of a-Cu and b-Pb, and its crystals were lath-shaped with much finer grains compared to the one fabricated under the normal conditions. In addition, the crystal grains grew along the tangential direction of the pulse current radiationally, from the guiding center to the surrounding area, caused by the Lorentz-force-induced gyroscopic motion. From the friction and wear experiments, the Cu-Pb alloy prepared by compound fields possesses a higher hardness, a lower friction coefficient and better wear resistance. Keywords: intense pulse and electromagnetic compound fields, Cu-37.4w/%Pb, Pb monotectic alloy, grain growth, wear resistance Avtorji~lanka so pripravili eno-evtekti~no zlitino Cu-37,4 mas. % Pb (Cu-Pb) v normalnih pogojih strjevanja in v pogojih intenzivnih sestavljenih pulzirajo~ih elektromagnetnih polj. Eno-evtekti~na Cu-Pb zlitina, pripravljena v normalnih pogojih strjevanja, je bila v glavnem sestavljena iz a-Cu in mo~no segregiranega Pb. Pri uporabi sestavljenih polj so odpravili segregacije Pb med izdelavo Cu-Pb zlitine. Zlitina je bila sestavljena iz homogenih trdnih raztopin a-Cu in b-Pb. Kristalna zrna so imela obliko letvic z mnogo bolj finimi kristalnimi zrni v primerjavi s tisto mikrostrukturo zlitine, ki je bila izdelana v normalnih pogojih strjevanja. Dodatno so ugotovili, da so kristalna zrna rasla vzdol`tangencialne smeri {irjenja tokovnih pulzov s sredi{~em vodenega preseka okolice, povzro~enih z Lorenzovo silo induciranega`iroskopskega gibanja. Preizkusi trenja in obrabe so pokazali, da ima Cu-Pb zlitina, pripravljena v sestavljenih poljih, ve~jo trdoto in manj{i koeficient trenja ter bolj{o odpornost proti obrabi. Klju~ne besede: intenzivna sestavljena pulzirajo~a in elektromagnetna polja, Cu-37,4 mas. % Pb, eno-evtekti~na zlitina, rast kristalnih zrn, odpornost proti obrabi