Akashi, Japan
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Murakami K.,Industrial Technology Center Of Okayama Prefecture | Nagata N.,Surtech Nagata Co. | Kanadani T.,Okayama University of Science
Materials Transactions | Year: 2015

The effect of alloying elements and the generation of hydrogen gas during zincate treatment and electroless nickel-phosphorus plating were studied by electron microscopy. Hydrogen gas was vigorously evolved during the zincate treatment for binary Al-2 at%Mg and Al-2 at%Si alloys, and the zincated surfaces were nonuniformly covered with excess coarse zinc particles due to the continuing oxidation of the substrate and reduction of proton and zincate ions. On the other hand, the surfaces of the ternary Al-2 at%Zn-0.2 at%Mg and Al-2 at%Zn-4.5 at%Mg alloys were immediately covered with a thin and uniform film of zinc. Magnesium in aluminum alloys and the excess precipitation of zinc were found to lower the adhesion of the electroless nickel-phosphorus plated films. When the zincated Al-2Mg and Al-2Si alloys were immersed in the plating solution, dissolution of the excess zinc generated hydrogen gas, and the plated films were poorly adhered to the substrates. Despite the thin and uniform zincate film, the plated film on the Al-2Zn-4.5Mg alloy was easily peeled off due to the voids formed between the plated film and the substrate. Magnesium in the alloy may suppress precipitation of the nickel and accelerate generation of hydrogen gas at the beginning of the plating. © 2015 The Japan Institute of Metals and Materials.


Murakami K.,Industrial Technology Research Institute of Okayama Prefectural Government | Nagata N.,Surtech Nagata Co. | Kanadani T.,Okayama University of Science
Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals | Year: 2013

Effect of alloying elements and generation of hydrogen gas dining zincate treatment and electroless nickel-phosphorus plating were studied by using electron microscopy. Hydrogen gas was vigorously evolved during the zincate treatment for binary Al-2 at%Mg and Al-2 at%Si alloys, and the zincated surfaces were nonuniformly covered with excess coarse zinc particles, due to continuing oxidation of the substrate and reduction of proton and zincate ions. On the other hand, the surfaces of ternary Al-2 at%Zn-0.2 at%Mg and Al-2 at%Zn-4.5 at%Mg alloys were immediately covered with thin and uniform film of zinc. Magnesium in aluminum alloys and the excess precipitation of zinc were found to lower adhesion of electroless nickel-phos-phorus plated films. When the zincated Al-2Mg and A1-2Si alloys were immersed in the plating solution dissolution of the excess zinc generated hydrogen gas and the plated films poorly adhered to the substrates. Despite the thin and uniform zincate film the plated film on Al-2Zn-4.5Mg alloy was easily peeled due to the voids formed between the plated film and the substrate. Magnesium in the alloy may suppress precipitation of nickel and accelerate generation of hydrogen gas at the beginning of the plating. ©2013 The Japan Institute of Metals and Materials.


Murakami K.,Industrial Technology Center Of Okayama Prefecture | Muraoka K.,Industrial Technology Center Of Okayama Prefecture | Nagata N.,Surtech Nagata Co. | Kanadani T.,Okayama University of Science
Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals | Year: 2014

Zinc-nickel-SiO2 electrodeposits have been produced from an acid sulphate bath. The co-deposition behavior of SiO2 and the macrothrowing power of platings were examined. The presence of SiO2 nanoparticles in the plating bath appears to change the alloy deposition behavior. The rate of nickel deposition was considerably decreased with SiO 2 nanoparticles in the bath. The macrothrowing power of plating was improved by adding the SiO2 nanoparticles in the bath. At an early stage of electrodeposition, it seems that the SiO2 nanoparticle acts as a nucleus of the precipitation. The SiO2 nanoparticles did not disperse uniformly in a plating film, but distributed only in the SiO 2 rich layer with about 50 nm in thickness formed beneath the surface. In addition, this SiO2 rich layer can improve the anticorrosive performance. Therefore, the zincic use can be suppressed, because the film thickness can be more thinned compared with zinc and zinc-nickel alloy electroplating. © 2014 The Japan Institute of Metals and Matenals.


Nagata N.,SURTECH NAGATA Co. | Murakami K.,Industrial Technology Center Of Okayama Prefecture | Kanetsuki H.,HIKARI LIGHT MATALS CO. | Kawai S.,HIKARI LIGHT MATALS CO. | Kanadani T.,Okayama University of Science
Advanced Materials Research | Year: 2014

The purpose of this study is to develop an Al-Mg-Zn series aluminum alloy casting suitable for the plating. We evaluated the influence of the metal structure on the plating process of both AC4CH and a developed aluminum alloy and then examined their suitability to plating. With the AC4CH-T6 casting containing the silicon, it was difficult to obtain a smooth surface by pretreatment process because of the surface irregularity between the hard and chemically stable eutectic silicon and the aluminum matrix. On the other hand, with the developed silicon-free alloy casting, it was possible to produce a smooth surface by pretreatment process, and this glossiness was superior to that of the AC4CH-T6 casting after electroless Ni-P plating. Furthermore, the plating property of the developed casting was also superior to that of the AC4CH-T6 casting, because the zinc deposit on the developed casting from the zincate treatment became uniformly, depending on the uniform displacement reaction. © (2014) Trans Tech Publications, Switzerland.


Nagata N.,Surtech Nagata Corporation | Kanadani T.,Okayama University of Science | Fukuhara M.,Okayama University of Science | Murakami K.,Industrial Technology Center Of Okayama Prefecture
Materials Science Forum | Year: 2014

In this study, the effect of electroless Ni-P plating on the fatigue strength of dilute Al-Si alloys was investigated. As results, the following points were clarified. Fatigue strength of the specimen subjected to zincate treatment only after furnace cooling treatment was almost the same as that of furnace cooling only. Fatigue strength of the specimen subjected to Ni-P plating after furnace cooling treatment, was reduced overall, except for high-stress region, rather than one of non-processing materials. Fatigue strength of the specimen subjected to Ni-P plating after aging treatment showed a clear increase in comparison with one of non-processing materials. Breaking elongation of the specimen subjected to Ni-P plating after aging treatment showed no significant changes in comparison with one of non-processing materials. On the other hand, fracture elongation of the specimen subjected to Ni-P plating after furnace cooling treatment reduced by half in comparison with one of non-processing materials. Especially, it seems that poor fatigue strength and ductility of plating materials are mainly caused due to interaction between surface precipitates and hydrogen gas. © (2014) Trans Tech Publications, Switzerland.


Kanadani T.,Okayama University of Science | Nagata N.,Surtech Nagata Corporation | Nakagawa K.,Okayama University of Science | Murakami K.,Industrial Technology Center Of Okayama Prefecture
Materials Science Forum | Year: 2014

Aging phenomena of Al-Zn alloys have been much investigated and many studies have been made on the change of mechanical properties on aging. Appearance of saw-tooth yielding (serration) in the stress-strain curve of tensile deformation has been reported in several reports. In this study, the relationship between occurrence of serration and reversion heat treatment was studied by tensile test on Al-Zn alloys. Serration was observed for the furnace cooled specimen, but not for the as-quenched one and the shortly aged one, which result is difficult to be interpreted by the Cottrell theory. The stress amplitude in the serration increased with increasing the time of annealing for reversion and then stayed at a constant value which might be interpreted by the Cottrell theory. The stress amplitude in the serration decreased with increasing the annealing temperature, which is contrary to the prediction by the Cottrell theory. The specimen directly annealed without aging and the one annealed after aging agreed well with each other in the tensile strength and the stress amplitude in the serration, which suggests solute clusters as the cause of serration. © (2014) Trans Tech Publications, Switzerland.


Hino M.,Industrial Technology Center Of Okayama Prefecture | Murakami K.,Industrial Technology Center Of Okayama Prefecture | Nagata N.,Surtech Nagata Co. | Ibata C.,Surtech Nagata Co. | And 2 more authors.
Materials Transactions | Year: 2013

In this study the effects of various surface treatments on the glossiness of AC4CH-T6 casting and newly developed bright aluminum alloy casting were examined With the AC4CH-T6 casting it was difficult to obtain a bright surface by buffing because of the surface irregularity between the hard eutectic silicon and the aluminum matrix. On the other hand with the developed silicon-free alloy casting it was possible to produce a bright surface by buffing and this glossiness was superior to that of the AC4CH-T6 casting covered with the decorative chrome electroplating. The glossiness of the developed casting decreased sharply after chemical polishing depending on the generation of local dissolution close to the intermetallic compound and pin-hole. However electropolishing under an optimum conditions helped realize a smooth and bright surface. As with the anodization from sulphuric acid solution glossiness of the developed alloy casting decreased because of the prior dissolution of the intermetallic compound. However anodization from the developed solution suppressed this dissolution forming a uniform oxide film. As a result bright surface could be produced for the developed alloy casting by anodization. © 2013 The Japan Society for Technology of Plasticity.

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