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Abstract

The influence of the cooling rate on the extent of precipitation hardening of cast aluminum alloy (ADC12) was investigated experimentally. This study explored the cooling rate of the solidification of Cu in the α-Al phase to improve the mechanical properties of ADC12 after an aging process (Cu based precipitation hardening). The solid solution of Cu occurred in the α-Al phases during the casting process at cooling rates exceeding 0.03 °C/s. This process was replaced with a solid solution process of T6 treatments. The extent of the solid solution varied depending on the cooling rate; with a higher cooling rate, a more extensive solid solution was formed. For the cast ADC12 alloy made at a high cooling rate, high precipitation hardening occurred after low-temperature heating (at 175 °C for 20 h), which improved the mechanical properties of the cast Al alloys. However, the low-temperature heating at the higher temperature for a longer time decreased the hardness due to over aging. Keywords: Aluminum alloy, Casting, Precipitation, Solid solution, Aging, Solidification rate
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Bibliography

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[9] Okayasu, M., Sahara, N. & Mayama, K. (2021). Effect of microstructural characteristics on mechanical properties of cast Al–Si–Cu alloy controlled by Na. Materials Science and Engineering. A (in press).
[10] Hamasaki, M. & Miyahara, H. (2013). Solidification microstructure and critical conditions of shrinkage porosity generation in die casting process of JIS-ADC12 (A383) alloy. Materials Transactions. 54(7), 1131-1139.
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[12] Okayasu, M. & Go, S. (2015). Precise analysis of effects of aging on mechanical properties of cast ADC12 aluminum alloy. Materials Science and Engineering. A 638, 208-218.
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Authors and Affiliations

M. Okayasu
1
N. Sahara
1
M. Touda
2

  1. Graduate School of Natural Science and Technology, Okayama University3-1-1 Tsushimanaka, Kita-ku, Okayama city, Okayama, 700-8530, Japan
  2. Kyowa Casting Co., Ltd.5418-3 Nishi Ebara-cho, Ibara city, Okayama, 715-0006, Japan
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Abstract

This study suggests a new way to modify the size and morphology of Al-Fe phases in modified AA 7075 by using an Fe-Mn solid solution powder as the precursor. When Fe and Mn are added in the form of a solid solution, the diffusion of Fe and Mn toward the Al is delayed, thus altering the chemical composition and morphology of the precipitates. The fine, spherical precipitates are found to provide a good balance between strength and ductility compared to the case where Fe and Mn are separately added.
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Bibliography

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Authors and Affiliations

Min Sang Kim
1 2
ORCID: ORCID
Dae Young Kim
3
ORCID: ORCID
Young Do Kim
1
ORCID: ORCID
Hyun Joo Choi
3
ORCID: ORCID
Se Hoon Kim
2
ORCID: ORCID

  1. Hanyang University, Department of Materials Science & Engineering, Seoul, Republic of Korea
  2. Metallic Material R&D Center, Korea Automotive Technology Institute, Cheonan-si, Republic of Korea
  3. Kookmin University, School of Materials Science and Engineering, Seoul, Republic of Korea
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Abstract

The Nb-Si based in-situ composite was produced by resistive sintering (RS) technique. In order to identify present phases, X-ray diffraction (XRD) analysis was used on the composite. XRD analysis revealed that the composite was composed of Nb solid solution (Nbss) and α-Nb5Si3 phases. The microstructure of the composite was characterized by using a scanning electron microscope (SEM). The energy-dispersive spectroscopy (EDS) was performed for the micro-analysis of the chemical species. SEM-EDS analyses show that the microstructure of composite consists of Nbss, Nb5Si3 and small volume fraction of Ti-rich Nbss phases. The micro hardness of constituent phases of the composite was found to be as 593±19 and 1408±33 Hv0.1, respectively and its relative density was % 98.54.

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Authors and Affiliations

Y. Garip
ORCID: ORCID
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Abstract

The review of peculiarity of growth and experimental results of the magneto-transport measurements (longitudinal magneto-resistance Rxx and the Hall resistance Rxy) over a wide interval of temperatures for several samples of Hg1−xCdxTe (x ≈ 0.13–0.15) grown by MBE is presented in this paper. An amazing temperature stability of the SdH-oscillation period and amplitude is observed in the entire temperature interval of measurements up to 50 K. Moreover, the quantum Hall effect (QHE) behaviour of the Hall resistance was shown in the same temperature interval. These peculiarities of the Rxx and Rxy for strained thin layers are interpreted using quantum Hall conductivity (QHC) on topologically protected surface states (TPSS). In the case of not strained layers it is assumed that the QHC on the TPSS contributes also to the conductance of the bulk samples. The experimental results on magneto-transport (QHC and SdH) obtained for the strained 100 nm thickness Hg1−xCdxTe layer are interpreted on the basis of the 8 × 8 kp model and an advantage of the Hg1−xCdxTe as topological insulators is shown. This article is an expanded version of the scientific reports presented at the International Conference on Semiconductor Nanostructures for Optoelectronics and Biosensors 2016 ICSeNOB2016, May 22–25, 2016, Rzeszow, Poland.

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Authors and Affiliations

G. Tomaka
J. Grendysa
M. Marchewka
P. Śliż
C.R. Becker
A. Stadler
E.M. Sheregii
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Abstract

The impact of small addition of zirconium in hypoeutectic commercial AlSi10MgCu alloys on their mechanical properties (hardness) in as cast and thermally treated conditions was investigated. Small addition of zirconium does not change significantly the as cast and heat-treated microstructure of investigated alloys except to reduce the SDAS and grain size of primary α-aluminium phases. Addition of zirconium up to 0.14 wt. percentage increases the hardness of investigated alloys in as cast conditions. The increase in the hardness of samples after various solid solution times can correlate very well with the formation of small needle like coherent Al3Zr particles.

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Authors and Affiliations

P. Hajduch
M.B. Djurdjevic
D. Bolibruchová
Z. Simicevic
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Abstract

The effect of the complex ligature with nickel and REM (Ce, La) aluminides on the structure formation, the nature of the distribution of the elements, and the microhardness of the structural constituents of Al-5 wt.% Cu aluminum alloy were investigated. On the example of microalloying of the Al-5 wt.% Cu alloy with a master alloy containing Ni and REM (Ce, La) aluminides it was shown that a redistribution of Al and Cu occurs in α-solid solution and eutectic. This is reflected in the refinement of α-solid solution and eutectic at 0.15 wt.% of the master alloy addition and, accordingly, increases the microhardness of α-solid solution by 100 MPa and eutectic by 125 MPa.

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Authors and Affiliations

E. Ri
K. Ri
V. Deev
E. Prusov

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