| Electrochemical surface reinforcement of Aluminum and its alloys was investigated detailedly in this paper. The first part of this paper researched the high voltage anodization and deposition (HVAD) of alumiunm and its alloys in neutral solutions. The properties, appearances, contents and structures of the obtained films were checked with SEM, EDS, XRD etc.. The mechanism and process of HVAD were also proposed. In neutral mixed electrolytes of Na2WO4, a smooth lustrous and grey non-metal film could be deposited on aluminum under the following conditions: film-formation promoter 25?.OgIl, film-formation complexing solvent I .5?.Og/l, Na2WO4 O.5.-.O.8gIl, peak current density &-12 A/din2, weak agitation. The obtained film showed a thickness of 5?01j.m, a microhardness of 300?40HV and an excellent resistance to acid and alkali. Film could be formed on many kinds of alloys, such as stainless aluminum, forging aluminum and so on, in this neutral HVAD system. The content elements of the film, as determined by EDS, were 0, Al, C, P and W. XRD investigation showed that it was a non-crystal film and aluminum oxides were the main composition phases together with some complicated compounds formed by aluminum and electrolyte species. The characteristic of the film, shown by SEM, was the very compact structure with pore density 30?0 per ~.tm2 and pore size 15?Onm. Further SEM study of the cross section found that it composed of a double-layer structure. The outer loose layer was l?~.tm thick, the inner compact layer 7?~.tm thick and connected with the substrate tightly. The process of HVAD could be devided into four stages, namely initial anodization and deposition stage, initial growth stage, rapid growth stage and spark discharge stage. The growth of film concentrated in the third stage with a rate of 2? ~imImin. The complex non-crystal film formed in neutral mixed solutions of Na2WO4 could be accounted for by a film growth mechanism which included the following steps under the surfacial chemical, electrochemical and Joule-heat interactions: (a) formation and accumulation of negative colloid particles comprising aluminum and electrolyte species; (b) uneven deposition of these particles; (c) dehydration and refrigeration in the deposition layer. This is not, of course, the only process going on at the anode. The formation of oxide-ceramic film on the alloy ZL1O9 by microarc oxidation method in mixed solutions of water glass was studied detailedly in the second part of this paper. The properties, monphologies, contents and structures of the obtained film were investigated with SEM, EDS, XR.D etc.. The effect of alloying of Al alloys on the properties of the film and its formation process were proposed, too. In mixed electrolytes of water glass, a smooth and even oxide-ceramic film could be obtained on the alloy ZLIO9 under the following conditions: NaOH 2?g/1, water glass 5? mill, Na2WO4 and EDTA, Na2Salt 4?g/1 according to 1:1 proportion in quantity, initial current density 30?0A/dm2, strong agitation. The obtained film was approximately 7O-.80~tm thick, 800HV hard. Similar oxide films could be procured on the alloys ZLIO8, ZLIIO, M124 and LY12 under the same conditions, but the alloying of Al alloys effected the contents and mirohardness of films fairly great. The ceramic film with high adhesion strength and hardness surpassing I200HV was synthesized on the alloy LF4, which was a material most fitting for microarc oxidation. In the present work, microarc... |
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