Additions of 1–2 Ni (wt. %) and hot deformation on the microstructure and hardness of A356 aged alloy were studied. The results show that the addition of this element generates the formation of ...Ni31Si12 and NiFe phases with high thermal stability. In addition, the presence of Ni into the Al matrix and precipitates of the second phase affect the precipitation kinetics, transformation sequence, growth rate, and slow loss of hardness in the system after reaching the maximum values. For example, the Ni additions contribute to generating the coexistence of β" precipitate and GP-I zones. Of all the strengthening mechanisms present, hardening by precipitation is the most influential in the hardness.
•Plastic deformations alter the precipitation kinetic.•Ni contribute to generating the coexistence of β" precipitate and GP-I zones.•Ni promotes high thermal stability on second phase precipitates.•Hardening by precipitation is the most influential in the hardness.•Ni promotes a slow loss of hardness after reaching the maximum hardness values.
The effects of the addition <2wt.% of Nickel and solid solution treatment times on microstructure and hardness of Al-Si-Cu alloy (A319) are reported. The results obtained show that Ni additions and ...heat treatments influence changes in microstructure, hardness and precipitation kinetics. The dendrites size and number density of Al-Cu-Ni and Al-Ni intermetallic compounds in as-cast condition are affected with Ni additions; however, occurs a reduction of Al-Cu-Ni phases at longer solution times (7h). The hardness values in alloyed samples with Ni are higher than those of reference samples, the maximum hardness peak are reached at shorter aging times; nonetheless, the decrease was slower during overaging step. The hardness values increase with Ni content ~4% HV where an increase of maximum hardness ~6% HV is reached with aging. After 10h of aging treatment at 170°C, the alloyed samples and not alloyed present different type of precipitates. In reference sample θ′-Al2Cu precipitates were identified, and in the alloyed samples, two types of coherent precipitates with different thickness and size were observed, in addition those precipitates present smaller size and higher number density than those observed in the reference alloy.
•Ni additions increase number density of Al-Cu-Ni, Al-Fe-Ni and Al-Ni intermetallic.•Ni additions increase the hardness of A319 alloy in as-cast and after T6-treatments.•Ni additions change the precipitation sequence of A319 Alloys during T6-treatments.•During overaging step, the growth and coarsening of precipitates are delaying in A319 alloy with Ni additions.
•Thermal and optical properties of Ho3+ doped tellurite glasses were studied.•Thermal stability values increase up to 26% with the addition of Ho3+.•Both thermal and optical properties seem to be ...directly related to each other.
It is well known that optical properties of soft glasses can be improved by modifying the glass matrix or the lanthanides ions concentration. However, in the case of soft glasses doped with Ho3+ ions the information is limited to a few manuscripts that deals mainly with optical properties, neglecting the effect that could have in thermal properties. The present work shows the fabrication and characterization of Ho3+ doped tellurite glass samples ((78-x)TeO2 - 10Nb2O5 - 10TiO2 - 2Al2O3 - xHo2O3, where x = 0, 0.5, 1, 2 and 3 mol.%), prepared by melting and quenching technique. Differential scanning calorimetry were measured. In order to observe the characteristic energy levels of Ho3+ ions, UV-Visible absorption spectra and luminescence spectra under 488 nm excitation were recorded. The results showed that the incorporation of Ho3+ has a positive influence on thermal and luminescent properties as the Ho3+ concentration increases up 0 to 2 mol.%.
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The strengthening mechanisms and precipitation behavior in AA2024 alloys with different Cu/Mg ratios (3.18 and 2.48) and different levels of plastic deformation (5 and 15%) were studied by X-ray ...diffraction, transmission electron microscopy and Vickers microhardness measurements. Results demonstrate that hardening depends significantly on the interaction of different strengthening mechanisms such as solid-solution, strain hardening and precipitation. Hardness is mostly influenced by precipitation, which in turn is modified by plastic deformation and the Cu/Mg ratio. Modification of Cu and Mg content as well as plastic deformation affect the precipitation behavior of the Al2CuMg (S) phase, since these lead to significant changes in size and numeric density of the S precipitates. A higher number density and a smaller size of S precipitates are obtained in the alloy with lower Cu/Mg ratio and 15% of thickness reduction.
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