Toyama-shi, Japan
Toyama-shi, Japan

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Saikawa S.,University of Toyama | Ebata Y.,Taiho Kogyo Co. | Terayama K.,University of Toyama | Ikeno S.,Hokuriku Polytechnic College | Yanagihara E.,Ahresty Corporation
Advanced Materials Research | Year: 2014

In recent years, Mg-Al-Zn system alloy has been used for the parts in the automobile for weight reductions. The age-hardening behavior of Mg-6mass%Al(-1mass%Zn)-0. 3mass%Mn alloys sand mold castings were investigated by Vickers hardness measurement and optical microscopic observation. Both alloys were solution-treated and then isothermal-aged at 473, 498 and 523K. For each aging temperature, both alloys were indicated age-hardening obviously, and decreased the value of maximum hardness and shorten time to maximum hardness with heighten aging temperature. Age-hardening curves for both alloys approximately showed the same change of hardness. However, these optical micrographs after aging treatment are observed different microstructure. In case of AM60 magnesium alloy, discontinuous precipitation preferentially occurred in aged sample. The volume fraction of discontinuous precipitation was larger than that of continuous precipitation. On the other hand, in case of AZ61 magnesium alloy, the volume fraction of continuous precipitation was larger than that of discontinuous precipitation. Furthermore, over-aged sample of both alloys were consisted of discontinuous precipitation, continuous precipitation and pre-precipitation area. © (2014) Trans Tech Publications, Switzerland.


Oe Y.,University of Toyama | Matsuda K.,University of Toyama | Nakamura J.,Tohoku University | Ikeno S.,Hokuriku Polytechnic College
Advanced Materials Research | Year: 2014

The effect of Cu or Ag addition on 2 step aging in Al-Mg-Si alloy has been investigated to understand precipitation for this alloy. The maximum hardness of two step aged alloy was higher with increasing pre-aging time for Al-Mg-Si alloy. There was no remarkable difference between the peak-hardness of the Ag addition alloy with and without pre-aging. The hardness decreased once for the Ag addition alloy aged at 473K just after pre-aged at 343K for 600ks and then increased to the peak hardness with increasing aging time, which means the reversion of the Ag addition alloy. © (2014) Trans Tech Publications, Switzerland.


Kawabata T.,University of Toyama | Nakagawa D.,University of Toyama | Saikawa S.,Ahresty Corporation | Nakamura J.,Tohoku University | And 2 more authors.
Materials Transactions | Year: 2013

Precipitation in Mg-Gd-Y (Gd:Y = 3: 1) alloys without Zr were investigated by HRTEM and SAED technique, and calculation of HRTEM images and electron density using DV-Xα to understand the relationship between precipitation in these alloys and HRTEM images. The diffuse scattering was obtained in as-quenched samples in each alloy by SAED and the mono-layer zones have been confirmed by HRTEM observation. The β′-phase was confirmed in the 2.9Gd0.8Y alloy by HRTEM, although the β″A-phase was confirmed in the 2.1Gd0.6Y alloy before the β′-phase. The β′-phase became predominant after prolonged aging. Zigzag lines were observed at the same time when the β′-phase appeared in the sample. HRTEM images obtained for these precipitates were compared with calculated HRTEM images. The contrast of atomic columns of the matrix in HRTEM image was calculated simplified model of cluster based on the Mg-matrix including one or some atomic columns of RE. This is also corresponded the distribution of electron density of the cluster. © 2013 The Japan Institute of Metals.


Nishikubo M.,University of Toyama | Matsuda K.,University of Toyama | Oe Y.,University of Toyama | Nakamura J.,Tohoku University | Ikeno S.,Hokuriku Polytechnic College
Materials Science Forum | Year: 2014

In this study, the aging behaviour of several Al-Mg-Si alloys (Al-Mg-Si-Cu, Al-Mg-Si-Ag and Al-Mg-Si-Cu-Ag) has been investigated by hardness tests and TEM observations. Comparing the age-hardening rate in the early period of these alloys, the alloys with Cu or/and Ag addition are faster than that of the base alloy, and the aging time to reach the maximum hardness of the alloys with Cu or/and Ag addition is shorter than that of the base alloy.Therefore the aging behaviour of that alloys has been investigated by TEM observations to understand the effect of Cu, Ag and Cu+Ag additions on aging precipitation. © (2014) Trans Tech Publications, Switzerland.


Matsuoka Y.,University of Toyama | Matsuda K.,University of Toyama | Watanabe K.,University of Toyama | Nakamura J.,Tohoku University | And 4 more authors.
Materials Transactions | Year: 2014

In this work, the early stage of precipitation have been investigated in a Mg2.9 at% Gd0.8 at% Y by high angle annular dark fieldscanning transmission electron microscopy (HAADF-STEM) and high resolution transmission electron microscopy (HRTEM). At the underaged condition, precipitates observed by HRTEM were classified as follows; mono-layer, a part of β, βA. By HAADF-STEM, zig-zag structure, small hexagonal network, and βA could be recognized. The small "super hexagons" are the first precipitates in this alloy. This structure, referred to as the pre β-phase, displays a short range similar to the one present in the D019 structure. This phase is formed during quenching and prevails over the zig-zag structure at the beginning of aging. The zig-zag contrast is one of the variations of this small hexagonal network or heterogeneous nucleation during aging. Finally, we concluded that the proposed precipitation sequence is as follows: SSSSpre β-phase having D019-SROβ-phaseβA-phase. The comparison of HRTEM, HAADF-STEM and simulated images have helped to clarify the meaning of HRTEM features. © 2014 The Japanese Society for Non-Destructive Inspection.


Watanab K.,University of Toyama | Ikeno S.,Hokuriku Polytechnic College | Yoshida T.,Aisin keikinzoku Co. | Murakami S.,Aisin keikinzoku Co. | Matsuda K.,University of Toyama
Advanced Materials Research | Year: 2014

Al-Zn-Mg alloy has been known as one of the aluminum alloys with the good age-hardening ability and the high strength among commercial aluminum alloys. The mechanical property of the limited ductility, however, is required to further improvement. In this work, three alloys, which were added Cu or Ag into the Al-Zn-Mg alloy, were prepared to compare the effect of the additional elements on the aging behavior. Ag or Cu added alloy showed higher maximum hardness than Ag or Cu free alloy. The h' phase were observed in all alloys peak-aged at 423K. According to addition of Ag or Cu, the number density of the precipitates increased than Ag or Cu free alloy. © (2014) Trans Tech Publications, Switzerland.


Matsuoka Y.,University of Toyama | Watanabe K.,University of Toyama | Saikawa S.,University of Toyama | Ikeno S.,Hokuriku Polytechnic College | Matsuda K.,University of Toyama
Advanced Materials Research | Year: 2014

The magnesium alloy containing rare earth element is known to show good heat resistance. In this study, Mg-Y, Mg-Gd and Mg-Gd-Y alloys including the same total amount of solute elements have been investigated to clarified the effect of the Y atom on age-hardening and precipitation using HRTEM, SAED technique and HRTEM simulation. The diffuse scattering by SAED was obtained in as-quenched condition in all alloys. In the specimen at as-quenched condition, the row contrasts consisted of bright and dark dots lying on the {1 1 00}Mg planes, which were considered to mono-layer were observed by HRTEM. © (2014) Trans Tech Publications, Switzerland.


Kawai A.,University of Toyama | Watanabe K.,University of Toyama | Matsuda K.,University of Toyama | Ikeno S.,Hokuriku Polytechnic College
Archives of Metallurgy and Materials | Year: 2015

The Al-Mg-Ge alloy is one of the age-hardening aluminum alloy after solution heat treatment. It has been proposed that the age-precipitation behavior of Al-Mg-Ge alloy is different from that of Al-Mg-Si alloy according to our previous works about the microstructure on Al-Mg-Ge alloy over-aged at 523K. For example, The hardness of peak aged Al-1.0mass%Mg2Ge alloy is higher than that of Al-1.0mass%Mg2Si alloy. The precipitates in the over-aged samples have been classified as some metastable phases, such as the β'-phase and Type-A precipitates and equilibrium phase of β-Mg2Ge by TEM observation. There a few reports about microstructure on Al-Mg-Ge alloys observed by TEM for different aging times. The age-precipitations structure of Al-Mg-Ge alloy has not been became clear. In this work, TEM observation was investigated the microstructure on Al-1.0mass%Mg2Ge alloy for difference aging times aged at 473K.


Hida S.,University of Toyama | Mikmekova S.,Academy of Sciences of the Czech Republic | Matsuda K.,University of Toyama | Ikeno S.,Hokuriku Polytechnic College
Materials Science Forum | Year: 2014

The precipitation sequence in Al-Mg-Si alloy is generally accepted as supersaturated solid solution →GP-zone → β'' →β' →β (Mg2Si). The effect of Ag or Cu in Al-Mg-Si alloy has been reported in a previous work [2-3]. There are few reports about the effect of Ag or Cu on the metastable phase and equilibrium phase in this alloy the system. Hexagonal plate like β-phase and Q-phase were observed in the Cu added alloy. This hexagonal-shaped β-phase has a unique orientation relationship to the Al matrix. This work was performed to compare the shape effect of the additional elements on the equilibrium phase. The hexagonal shape precipitate was observed both in Cu or Ag added alloys aged at 673K. © (2014) Trans Tech Publications, Switzerland.


Kawai A.,University of Toyama | Matsuura K.,University of Toyama | Watanabe K.,University of Toyama | Matsuda K.,University of Toyama | Ikeno S.,Hokuriku Polytechnic College
Materials Science Forum | Year: 2014

It is known that Al-Mg-Ge alloys show a similar precipitation sequence to that of Al-Mg-Si alloys, and that ther equilibrium phase is β-Mg2Ge according to the phase diagram. In this study, the precipitation sequence and age-hardening behavior of Al-1.0mass%Mg2Ge alloys has been investigated by hardness test, write out in full first time used TEM and HRTEM observations on.The hardness curves showed no big difference between peak values hardness for samples aged at 423, 473 and 523K. The precipitates in the peak-aged samples have been classified as some metastable phases, such as the β'-phase and parallelogram-type precipitates by HRTEM observation. The large precipitates are similar to the A-type precipitate in the Al-Mg-Si alloy with excess Si. © (2014) Trans Tech Publications, Switzerland.

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