Effect of an Addition of Silver on the Age Hardening and the Formation of a Soft Surface Layer in an Al-12mass%Zn Alloy

2006 ◽  
Vol 519-521 ◽  
pp. 1883-1888 ◽  
Author(s):  
Teruto Kanadani ◽  
Keiyu Nakagawa ◽  
Norio Hosokawa ◽  
Akira Sakakibara ◽  
Koji Murakami ◽  
...  
Keyword(s):  
Surface Layer ◽  
Grain Boundaries ◽  
Resistivity Measurement ◽  
Hardness Test ◽  
Age Hardening ◽  
Electrical Resistivity Measurement ◽  
Quenching Temperature ◽  
Soft Surface ◽  
Long Time ◽  
Zn Alloy

The aging of Al-Zn alloys has been vastly studied for decades. In the previous paper, 0hta et al. studied carefully the hardness of the alloy during aging and revealed the existence of softer regions near the surface and the grain boundary than the interior of the specimen even after aging for a long time. Electrical resistivity measurement and X-ray small angle scattering experiment together with hardness test suggested that in these regions vacancy decay to the surface and grain boundaries was severe, thus the growth of GP zones were suppressed and therefore age hardening was retarded. Also, it is well-known that an addition of a small amount of Ag raised solvus temperature of GP zones. In this paper, soft surface layer formed in an Al-12mass%Zn alloy is studied by adding small amount of Ag by means of hardness test and resistometry. Addition of Ag more than 0.1% decreases the thickness of soft surface layer as well as accelerates age hardening rate and suppresses the formation of soft region near the grain boundaries. Higher quenching temperature also reduces the thickness of soft surface layer. Together with the behavior of aging curves of the specimen with various thicknesses, the origin of the soft surface layer is confirmed to be the effective role of surface as sinks for vacancies.

Soft Surface Layer of Age-Hardened Al-Zn Alloys and Its Effect on the Fatigue Strength

2007 ◽  
Vol 345-346 ◽  
pp. 391-394
Author(s):  
Teruto Kanadani ◽  
Keiyu Nakagawa ◽  
Norio Hosokawa
Keyword(s):  
Surface Layer ◽  
Fatigue Strength ◽  
Tensile Loading ◽  
Soft Surface ◽  
Long Time ◽  
Number Of Cycles ◽  
Zn Alloy ◽  
Cycles To Failure ◽  
Zn Alloys ◽  
Hardened Surface

The surface layer of binary Al-Zn alloy specimen, ever after a long time aging, remains softer than the interior when the specimens are age-hardened at around room temperature after quenching from high temperature. In this study, effects of the soft surface layer on the fatigue strength of Al-Zn alloys were studied under repeated tensile loading. Vickers microharhness test revealed that there existed less hardened region in the vicinity of grain boundary and specimens surface, and that the region extends 50 to 100μm from the surface inward. From the plot of the stress amplitude against the number of cycles to failure, it is concluded that the presence of less hardened surface layer increases fatigue resistance of age-hardened Al-Zn alloys containing 8 to 16 mass%Zn under the repeated tensile loading.

Effect of an Addition of Silver on the Age Hardening and the Formation of a Soft Surface Layer in an Al-12mass%Zn Alloy

2006 ◽  
pp. 1883-1888
Author(s):  
Teruto Kanadani ◽  
Keiyu Nakagawa ◽  
Norio Hosokawa ◽  
Akira Sakakibara ◽  
Kouji Murakami ◽  
...  
Keyword(s):  
Surface Layer ◽  
Age Hardening ◽  
Soft Surface ◽  
Zn Alloy

Nanocluster Formation and Two-Step Aging Behavior of Rapid Hardening Al-Mg-Cu(-Ag) Alloys

2014 ◽  
Vol 794-796 ◽  
pp. 996-1001 ◽  
Author(s):  
Mami Mihara ◽  
Equo Kobayashi ◽  
Tatsuo Sato
Keyword(s):  
Electrical Resistivity ◽  
Base Alloy ◽  
Resistivity Measurement ◽  
Hardness Measurement ◽  
Age Hardening ◽  
Peak Hardness ◽  
Electrical Resistivity Measurement ◽  
Scanning Calorimetry ◽  
Aging Response ◽  
Two Stages

The characteristic age-hardening response of Al-3.0Mg-1.0Cu (mass%) alloys with and without Ag addition has been investigated by the hardness measurement, differential scanning calorimetry (DSC) and electrical resistivity measurement. The alloy compositions locating in the (α+S+T) phase field of the Al-Mg-Cu phase diagram are known to be effective to harden in two stages separated by a distinct and often prolonged hardness plateau. The first stage of hardening occurs very rapidly (e.g. within 60 s at 443 K) and contributes to increase hardness as much as 50 % of the total age-hardening. In the Ag-added alloy, the hardness change during the first stage of hardening is larger and the plateau stage is shortened as a result of the fast arrival at the second stage of hardness. Small amount of Ag changes the age hardening response of the Base alloy dramatically. In the low temperature aging, the incubation stage at which no clear hardness and electrical resistivity increase appears for a long period before the first stage of hardening. After the pre-aging at this incubation period, a characteristic two-step aging response is observed. The peak hardness dramatically changes in the Al-3.0Mg-1.0Cu alloy, while no clear change in the Ag-added alloy.

Age-Hardening Behavior of Pd-Ag-Sn-In-Zn Alloy

2014 ◽  
Vol 1028 ◽  
pp. 14-19 ◽  
Author(s):  
Hai Jun Wu ◽  
Xiao Qing Zuo ◽  
Ying Wu Wang ◽  
Kun Hua Zhang ◽  
Yu Zeng Chen
Keyword(s):  
Aging Time ◽  
Early Stage ◽  
Energy Dispersive Spectrometer ◽  
Hardness Test ◽  
Age Hardening ◽  
Aged Alloy ◽  
X Ray Diffraction ◽  
Electron Microscopic ◽  
Scanning Electron Microscopic ◽  
Zn Alloy

Pd-Ag-Sn-In-Zn alloy was subjected to isothermal aging treatments at 400°C, 500°C, and 650°C. Age-hardening behaviour and related microstructure changes of the aged alloy were studied by means of hardness test, X-ray diffraction (XRD), scanning electron microscopic (SEM) and energy dispersive spectrometer (EDS). The results indicate that the hardness of the alloy reaches a highest value of 348Hv after aging at 650°C for 20min. Further increasing the aging time leads to softening. The hardening of the alloy at early stage of the age-hardening at 650°C is ascribed to the formation of lamellar (α1+ β) precipitates along the grain boundaries of α matrix. The softening of the alloy occurred by further increasing aging time is caused by the coarsening of the precipitates.

Effect of Small Addition of Silver on the Formation of a Soft Surface Layer in Age-Hardened A1-12mass%Zn Alloy

1992 ◽  
Vol 129 (1) ◽  
pp. K1-K4 ◽  
Author(s):  
T. Kanadani ◽  
A. Sakakibara ◽  
N. Hosokawa ◽  
T. Kaneeda
Keyword(s):  
Surface Layer ◽  
Small Addition ◽  
Soft Surface ◽  
Zn Alloy

Effect of Surface and Grain Boundary on the Reversion of Al-Zn Alloys

2014 ◽  
Vol 794-796 ◽  
pp. 1211-1216
Author(s):  
Keiyu Nakagawa ◽  
Teruto Kanadani
Keyword(s):  
Grain Boundary ◽  
Hardness Test ◽  
Age Hardening ◽  
Micro Hardness ◽  
Zn Alloy ◽  
Vickers Micro Hardness ◽  
Zn Alloys ◽  
Effective Source ◽  
Effect Of Surface

Age-hardening of Al-Zn alloy after quenching develops inhomogeneously due to the effect of surface as a vacancy sink and grain boundary as an easy path. In this study, reversion of the age-hardened Al-Zn alloys, in which ellipsoidal GP zones were formed, was investigated by Vickers micro-hardness test. Ellipsoidal GP zones were reverted more quickly near the surface and grain boundary than in the interior, as spherical GP zones in Al-10%alloy did. It is considered that the surface and grain boundary plays a role of effective source for vacancies, in addition to the interior source such as dislocations, as in the case of the reversion of spherical GP zones.

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