Abstract
The stress and strain play an important role in strengthening of the precipitation-hardened Aluminum (Al) alloys. Despite the determination of relationship between the mechanical properties and the precipitation existing in the microstructure of these alloys, a quantitative analysis of the local stress and the strain fields at the hardening-precipitates level has been seldom reported. In this paper, the microstructure of a T8 temper AA2195 Al alloy is investigated using aberration corrected scanning transmission electron microscopy (AC-STEM). The strain fields in Al matrix in the vicinity of observed precipitates, namely T1 and β' , are determined using geometric phase analysis (GPA). Young's modulus (Ym ) mapping of the corresponding areas is determined from the valence electron energy loss spectroscopy (VEELS) measured bulk Plasmon energy (Ep ) of the alloys. The GPA-determined strains were then combined with VEELS-determined Ym under the linear theory of elasticity to give rise the local stresses in the alloy. The obtained results show that the local stresses in Al matrix having no precipitates were in the range of 138 ± 2 MPa. Whereas, in the vicinity of thin and thick T1 platelet shape precipitates, the stresses were found to be about 202 ± 3 MPa and 195 ±3 MPa, respectively. The stresses measured in the vicinity of β' spherical shape precipitates found out to be 140 ± 3 MPa which was near to the local stress value in Al matrix. Our findings suggest that the precipitate hardening in T8 temper AA2195 Al alloy predominantly stems from thin T1 precipitates.
Highlights
In the last decade, perovskite materials have become the preferred choice for many photonic applications, due to their unique crystal structures, excellent carrier mobility, high absorption coefficients, and tuned direct band gaps.perovskite-based devices can be manufactured using simple and flexible processes with low production costs, such as solution processing.[1−14] The performance of perovskites as solar light-harvesting materials in photovoltaics[1,2,15] and photodetectors[7] is extraordinary
We explored the potential of CsPbBr3 perovskite quantum dots (PQDs) thin films as laser-active media using, for example, a picosecond laser as an optical pumping source
The lattice fringes of a single quantum dots (QDs) with an interplanar spacing of ∼0.25 nm are visible in the inset of Figure 1b. This corresponded to the distance between adjacent (200) lattice planes, which was confirmed by performing X-ray diffraction (XRD) analysis
Summary
Perovskite materials have become the preferred choice for many photonic applications, due to their unique crystal structures, excellent carrier mobility, high absorption coefficients, and tuned direct band gaps. A low ASE threshold can be attributed to trapping states with small cross sections, slow Auger recombination, and low rates of bimolecular recombination.[73] The dimensions of quantum dots are comparable to the de Broglie wavelength of electrons, so the energy difference between two adjacent levels exceeds the product of the absolute temperature (T) and the Boltzmann constant (k) This results in quantum confinement, which limits the mobility of electrons and holes.[74] The CsPbBr3 PQDs combined the advantages of perovskites and quantum confinement. ■ Figure 8. (a) Integrated PL versus injected carrier density (n) and (b) BGR versus n1/3 of CsPbBr3 PQDs
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