Effects of Cold Working on Precipitation in Age-hardenable Alloys

Experiments have been carried out to examine the effects of cold working on the rate of precipitation in high purity copper alloys and aluminium alloys with measurements of electrical resistance, micro-hardness and thermo-electromotive force, X-ray Laue photographs and small angle scatter method. The correlation between cold working and the excess vacancies retained in quenching was investigated in water quenched and air cooled specimens. The experiments provided evidence that cold working accelerates the process at higher ageing temperatures, and that at lower ageing temperatures the rate of precipitation of cold worked specimens is less than that of unworked materials. In Al-Ag and Al-Cu alloys, the formation of zones was hindered and the precipitation of the more stable intermediate phases γ´ or θ´ was accelerated. The suppressive effect of cold working is thought to be a general phenomenon in age-hardenable alloys, because the effect is also found in alloys such as Cu-Cr alloys in which the precipitation sequence is simple. The mechanism of retarding by cold working is due to two effects : one is the sweeping out of the quenched-in vacancies, which are necessary for solute diffusion, by the motion of jogs in dislocations during cold working, and the other is the formation of many smaller clusters of enriched solute atoms which were formed by the stronger binding interaction energies between solute atoms and the lattice defects introduced by cold working

Aging Characteristics and Effects of Plastic Deformation on Precipitation in Al-4% Cu and Al-20% Ag Alloys with or without Trace Elements

The experiments have been carried out to examine the effects of plastic deformation and addition of small amounts of third elements on the aging process in Al-4%Cu and Al-20%Ag alloys by the X-ray Laue method, micro-hardness measurements, transmission electron microscopic studies and resistivity measurements. In binary Al-4% Cu alloys, the plastic deformation immediately after quenching retards the growth of G.P. (1) and G.P. (2), and accelerates the nucleation of the θ′ phase. In Al-20% Ag alloys, similar results are obtained. In undeformed ternary Al-Cu alloy, the retarding effects of third elements on aging become stronger in the order Be<Ti<Zr. In Al-Cu-Zr alloys, the plastic deformation much accelerates the growth of G.P. (1). The role of excess vacancies on aging and the interaction between dislocation and precipitates are discussed

On Precipitation Phenomena in Magnesium-Zinc Alloys

The ageing characteristics of magnesium-zinc alloys in the composition range from 3.2 to 19.0 wt.% zinc were studied at temperatures from 70° to 200°C mainly with X-ray diffraction methods and electron-microscopic observations with thin foils. The G.P. zones were confirmed to exist on the {1011} matrix planes. The transition phase on the {1010} matrix planes is MgZn´ indistinguishable from the hexagonal Laves phase MgZn₂. The effects of plastic deformation were examined with direct observations by thin foils. The formation of G.P. zones on the {1011} matrix plane was hindered by cold working after water quenching, while the rates of precipitation of the transition phase β´ and equilibrium phase β were accelerated

Electron-Microscopic Investigation on Precipitation Phenomena in Aluminium-Zinc Alloys

The precipitation process, its relation with lattice defects and the effect of cold working on precipitation and grain boundary reaction in the aluminium alloys containing ll.2, 17.4, 28.3 and 40.8% zinc respectively were investigated by means of X-ray diffraction, hardness measurements and transmission electron microscopy. It was found that face-centered cubic transition precipitates were formed in granular shape in ll.2% or 17.4% zinc alloys and were plate-like in 28.3% zinc alloys. The plate-like transition precipitates were formed on {110} matrix planes, perhaps preferentially on the prismatic dislocation loops. The results are shown to be consistent with the hypothesis that in the quenched alloys precipitation occurs on prismatic dislocation loops that result from the condensation of quenched-in vacancies. In Al-28.3 and 40.8% Zn alloys, the grain boundary reaction is predominant at lower aging temperatures

Transmission Electron Microscopic Investigation on Recrystallization and Precipitation of Magnesium and Magnesium Alloys

Experiments have been carried out to examine aging characteristics, recrystallization phenomena and effects of plastic deformation after water-quenching on the precipitation of Mg-Th alloys in the composition range from 1.7 to 4.0 w/t% thorium as compared with pure magnesium, Mg-Zn and Mg-Al alloys mainly with electron microscopic observations in thin foils. In Mg-4.0% Th alloys, G. P. zones were confirmed to exist before the appearance of the transition phase Mg2Th in accordance with the result of measurements of electrical resistance. The presence of thorium in a magnesium alloy greatly retarded such processes as recovery and recrystallization. This slowing up process seems to be reflected in the slow precipitation rate of Mg-Th compounds. The effects of cold working on precipitation in these alloys are not simple but complex

Röntgenographische Untersuchungen Über den Ausscheidungsvorgang in einer Kupfer-Beryllium-Legierung und den Einfluss von Magnesium- oder Zink-Zusätzen auf ihr Verhalten

Die Untersuchungen über das Ausscheidungsverhalten von Kupfer-1.8 Gew. -% Beryllium Legierungen ohne und mit etwa 0.2 Atom. -% Magnesium oder Zink wurden röntgenographisch mittels Laue-, Kleinwinkel-Streuung-, Einkristall-Schwenk-, und Debye-Scherrer- Aufnahmen durchgeführt. Die Kinetik der Ausscheidung kann wie folgt dargestellt werden: G.P.-Zonen auf {100} Flächen des α- Mischkristalls, Zwischenphase-γ' mit einem Zonenzustand, und Gleichgewichtsphase-r. Bei der magnesiumhaltigen Legierung hemmt die Abnahme der Übersättigung des Mischkristalls an Beryllium-Atomen zufolge einer bedeutenden Ausscheidung der Zwischenphase-γ' die diskontinuierliche Ausscheidung. Andererseits wird bei der zinkhaltigen Legierung das Wachstum der G.P.-Zonen aktiv, und die feineren Aus-scheidungsteilchen der γ'-Phase, die in dieser Arbeit γ'-Zonen bezeichnet werden, können nicht größer werden. Die mehren übersättigten Beryllium-Atome und die Spannung um die G.P.-Zonen und die γ'-Zonen verursachen die diskontinuierliche Ausscheidung. Für die beschleunigte Bilding der G.P.-Zonen bei Zusätzen von Magnesium oder Zink kann dahingehend gedeutet werden, daß sich die bei der Zonen-Bildung Spannungen durch diese Elemente vermindern, und daß die bei der Zonen-Bildung behilflichen Leerstellen in diesen Legierungen stabiler werden

Possibility of the magnetic field effect on the thermal decomposition of N2O : Molecular dynamics simulation

Molecular dynamics (MD) model calculations for the thermal decomposition of N2O with external magnetic field were performed. The effect of external magnetic field was modeled by parameterization of the interaction term between the singlet and triplet potential surfaces. It was suggested that the increase of the rate constant by external magnetic field could be explained by means of the increase of interaction term which is dependent on the angle of the Jacobi coordinate

Patient affect and caregiver burden in dementia

BACKGROUND: Numerous studies focusing on the burden of caregivers of dementia patients have been published. However, there have been few studies focusing on positive affect as an important factor affecting the caregiver burden, and only a few studies comparing the caregiver burden between different dementia diseases have been reported. METHODS: Three hundred and thirty-seven consecutive caregivers of people with dementia participated in this study. The caregiver burden was evaluated by the short version of the Japanese version of the Zarit Burden Interview. RESULTS: Positive affect scores had a significant relationship with the scores of the short version of the Zarit Burden Interview. Caregivers for patients with dementia with Lewy bodies or frontotemporal dementia suffered from a greater burden than those for patients with Alzheimer's disease dementia. CONCLUSIONS: The caregiver burden differed between people caring for patients with different dementia diseases. Positive affect of dementia patients has a significant relationship with caregiver burden, independently from neuropsychiatric symptoms of patients

The leech excitatory peptide, a member of the GGNG peptide family: isolation and comparison with the earthworm GGNG peptides

AbstractA member of the GGNG peptide family was isolated from Hirudo nipponia (leech). GGNG peptides had only been isolated previously from earthworms. The C-terminus structure of the leech peptide, LEP (leech excitatory peptide), was –Gly–Gly–Asn–amide, while that of the earthworm peptides, EEP (earthworm excitatory peptide), was –Gly–Gly–Asn–Gly. LEP exerted 1000-fold more potent activities on leech gut than did EEP-2. On the other hand, EEP-2 was 1000-fold more potent than LEP on the crop-gizzard of the earthworm. Analog peptides of LEP and EEP-2 were synthesized, and the myoactive potency of each analog on the leech and earthworm tissues was compared