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Ultrasonic melt treatment (UST) was applied to Al-7Si-2Cu-1Mg melt at various temperatures of 620, 650, 700 and 785 °C. MgAl2O4 particles which were often found to be densely populated along oxide films, became effectively dispersed and well-wetted by UST. Transmission electron microscopy work combined with crystallography analysis clearly indicates that MgAl2O4 particles can act as α-Al nucleation site with the aid of UST. However, with UST, grain refinement occurred only at temperature of 620 °C and the grain size increased from 97 to 351 μm with increase of melt temperature to 785 °C for UST. In quantitative analysis of grain size and MgAl2O4 particle diameter, it was found that ultrasonic de-agglomeration decreased mean particle size of the MgAl2O4 particles, significantly reducing size from 1.2 to 0.4 μm when temperature increased from 620 to 785 °C. Such a size reduction with increased number of MgAl2O4 particles does not always guarantee grain refinement. Thus, in this work, detailed condition for achieving grain refinement by UST is discussed based on quantitative measurement. Furthermore, we tried to suggest the most valid grain refinement mechanism among the known mechanisms by investigation of the relationship between grain size and particle size with variation of melt temperature.

In the present study, pull-out and pull-off tests were conducted to examine the bond strength between an inorganic cement adhesive (hereinafter referred to as the “matrix”) and a textile, which composed a fabric-reinforced cementitious matrix (FRCM). The matrix was developed by mixing slag and short fibers in an attempt to improve the alkali resistance and compressive strength. The developed matrix was examined with regard to its alkali resistance, water resistance, and void distribution. Bond tests were conducted in two parts: a pull-out series and pull-off series. The type of textile (carbon or basalt) and the weaving methods were selected as test parameters. These tests were performed in accordance with the methods described in ISO10406-1 (pull-out) and ASTM C1583 (pull-off). The test results showed that the developed matrix was superior to existing mortar methods in terms of alkali resistance, water resistance, and compressive strength. Additionally, the FRCM in which carbon textiles were used exhibited excellent bond performance.

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