The paper presents results of compressive strength investigations of EN AC-44200 based aluminum alloy composite materials reinforced
with aluminum oxide particles at ambient and at temperatures of 100, 200 and 250C. They were manufactured by squeeze casting of the
porous preforms made of α-Al2O3 particles with liquid aluminum alloy EN AC-44200. The composite materials were reinforced with
preforms characterized by the porosities of 90, 80, 70 and 60 vol. %, thus the alumina content in the composite materials was 10, 20, 30
and 40 vol.%. The results of the compressive strength of manufactured materials were presented and basing on the microscopic
observations the effect of the volume content of strengthening alumina particles on the cracking mechanisms during compression at
indicated temperatures were shown and discussed. The highest compressive strength of 470 MPa at ambient temperature showed
composite materials strengthened with 40 vol.% of α-Al2O3 particles.
The paper presents the results of research of impact strength of aluminum alloy EN AC-44200 based composite materials reinforced with
alumina particles. The research was carried out applying the materials produced by the pressure infiltration method of ceramic preforms
made of Al2O3 particles of 3-6m with the liquid EN AC-44200 Al alloy. The research was aimed at determining the composite resistance
to dynamic loads, taking into account the volume of reinforcing particles (from 10 to 40% by volume) at an ambient of 23°C and at
elevated temperatures to a maximum of 300°C. The results of this study were referred to the unreinforced matrix EN AC-44200 and to its
hardness and tensile strength. Based on microscopic studies, an analysis and description of crack mechanics of the tested materials were
performed. Structural analysis of a fracture surface, material structures under the crack surfaces of the matrix and cracking of the
reinforcing particles were performed.
The paper deals with spectral and lasing characteristics of
thulium-doped optical fibers fabricated by means of two doping
techniques,
i.e. via a conventional solution-doping method and via
a nanoparticle-doping method. The difference in fabrication was the
application of a suspension of aluminum oxide nanoparticles of defined
size instead of a conventional chloride-containing solution. Samples of
thulium-doped silica fibers having nearly identical chemical composition
and waveguiding properties were fabricated. The sample fabricated by
means of the nanoparticle-doping method exhibited longer lifetime,
reflecting other observations and the trend already observed with the
fibers doped with erbium and aluminum nanoparticles. The fiber
fabricated by means of the nanoparticle-doping method exhibited a lower
lasing threshold (by ~20%) and higher slope efficiency (by ~5% rel.).
All these observed differences are not extensive and deserve more
in-depth research; they may imply a positive influence of the
nanoparticle approach on properties of rare-earth-doped fibers for fiber
lasers.
Metal matrix composites (MMC) are finding application in many fields such as aerospace and automobile industries. This is due to their advantages such as light weight and low cost. Among all the available non-traditional machining processes, wire electric discharge machining (WEDM) is found to be a suitable method for producing complex or intricate shapes in composite materials. In this study, an aluminum metal matrix composite (AMMC) with 6% and 8% weight (wt) fraction of Al2O3 is prepared through the stir casting process. The fabricated AMMC specimen is machined using WEDM, considering various process parameters such as wt % of reinforcement, gap voltage (Vg), peak current (IP) wire tension (WT) and dielectric pressure (Pd). Output responses such as the machining rate (MR) and surface roughness (Ra) of the slots are analyzed by conducting L18 mixed orthogonal array (OA) experiments. The experiments are analyzed using techniques for order preference by similarity to ideal solution (TOPSIS) and analysis of variance (ANOVA). Based on the analyses, the optimum combination of process parameters for better MR and Ra is as follows: wt % = 6 gm, Vg = 53 V, Ip = 8 A, WT = 11 g, Pd = 13 bar. The optimum level of process parameters for MR and Ra are 1.5 mm/min and 3.648 µm, respectively. Based on ANOVA, the peak current is found to have a significant influence on MR and Ra. Moreover, based on a scanning electron microscope (SEM) image, the presence of micro-ridges, reinforcement, micro-craters, micro-cracks, recast layers and oxide formation are all analyzed on the surface being machined.