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 results of bend tests at elevated temperatures of aluminium alloy EN AC-44200 (AlSi12) based composite materials
reinforced with aluminium oxide particles. The examined materials were manufactured by squeeze casting. Preforms made of Al2O3
particles, with volumetric fraction 10, 20, 30 and 40 vol.% of particles joined with sodium silicate bridges were used as reinforcement. The
preforms were characterised by open porosity ensuring proper infiltration with the EN AC-44200 (AlSi12) liquid alloy. The largest
bending strength was found for the materials containing 40 vol.% of reinforcing ceramic particles, tested at ambient temperature. At
increased test temperature, bending strength Rg of composites decreased in average by 30 to 50 MPa per 100°C of temperature increase.
Temperature increase did not significantly affect cracking of the materials. Cracks propagated mainly along the interfaces particle/matrix,
with no effect of the particles falling-out from fracture surfaces. Direction of cracking can be affected by a small number of
agglomerations of particles or of non-reacted binder. In the composites, the particles strongly restrict plastic deformation of the alloy,
which leads to creation of brittle fractures. At elevated temperatures, however mainly at 200 and 300°C, larger numbers of broken,
fragmented particles was observed in the vicinity of cracks. Fragmentation of particles occurred mainly at tensioned side of the bended
specimens, in the materials with smaller fraction of Al2O3 reinforcement, i.e. 10 and 20 vol.%.
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.
In this study, ODS ferritic stainless steels were fabricated using a commercial alloy powder, and their microstructures and mechanical properties were studied to develop the advanced structural materials for high temperature service applications. Mechanical alloying and uniaxial hot pressing processes were employed to produce the ODS ferritic stainless steels. It was revealed that oxide particles in the ODS stainless steels were composed of Y-Si-O, Y-Ti-Si-O, and Y-Hf-Si-O complex oxides were observed depending on minor alloying elements, Ti and Hf. The ODS ferritic stainless steel with a Hf addition presented ultra-fine grains with uniform distributions of fine complex oxide particles which located in grains and on the grain boundaries. These favorable microstructures led to superior tensile properties than commercial stainless steel and ODS ferritic steel with Ti addition at elevated temperature.
In this study, to investigate effects of rhenium addition on the microstructures and mechanical properties, 15Cr-1Mo ODS ferritic steels with rhenium additions were fabricated by the mechanical alloying, hot isostatic pressing, and hot rolling processes. Unremarkable differences on grain morphologies and nano-oxide distributions were estimated in the microstructure observations. However, the ODS ferritic steels with 0.5 wt.% rhenium showed higher tensile and creep strengths at elevated temperature than that without rhenium. It was found that rhenium is very effective to improve the mechanical properties.
Ferrtic/martensitic and ODS steels were fabricated by the mechanical alloying process, and their microstructures and mechanical properties were investigated. The 9Cr-1W and 9Cr-1W-0.3Ti-0.35Y2O3 (in wt.%) steels were prepared by the same fabrication process such as mechanical alloying, hot isostatic pressing, and hot rolling processes. A microstructural observation of these steels indicated that the Ti and Y2O3 additions to 9Cr-1W steel were significantly effective to refine the grain size and form nano-sized Y-Ti-O oxide particles. As a result, the tensile strengths at room and elevated temperatures were considerably enhanced. Considerable improvement of the creep resistances at 700°C was also evaluated. It is thus concluded that 9Cr-1W ODS steel with Ti and Y2O3 additions would be very effective in improving the mechanical properties especially at elevated temperatures.