The paper presents relationships between the degree of structure fineness and feeding quality of the Al – 20 wt.% Zn (Al-20 Zn) alloy cast into a mould made from sand containing silica quartz as a matrix and bentonite as a binder, and its damping coefficient of the ultrasound wave at frequency of 1 MHz. The structure of the examined alloy was grain refined by the addition of the refining Al-3 wt.% Ti – 0.15 wt.%C (TiCAl) master alloy. The macrostructure analysis of the initial alloy without the addition of Ti and the alloy doped with 50-100 ppm Ti as well as results of damping experiments showed that the structure of the modified alloy is significantly refined. At the same time, its damping coefficient decreases by about 20-25%; however, it still belongs to the so called high-damping alloys. Additionally, it was found that despite of using high purity metals Al and Zn (minimum 99,99% purity), differences in the damping coefficient for samples cut from upper and bottom parts of the vertically cast rolls were observed. These differences are connected with the insufficient feeding process leading to shrinkage porosity as well as gases present in metal charges which are responsible for bubbles of gas-porosity.
The paper is devoted to grain-refinement of the medium-aluminium zinc based alloys (MAl-Zn). The system examined was sand cast Zn10 wt. %. Al binary alloy (Zn-10Al) doped with commercial Al-3 wt. % Ti – 0.15 wt. % C grain refiner (Al-3Ti-0.15C GR). Basing on the measured attenuation coefficient of ultrasonic wave it was stated that together with significantly increased structure fineness damping decreases only by about 10 – 20%. The following examinations should establish the influence of the mentioned grain-refinement on strength and ductility of MAl-Zn cast alloys.
The paper presents results of measuring attenuation coefficient of the Al-20 wt.% Zn alloy (AlZn20) inoculated with different grain refiners. During experiments the melted alloys were doped with Al-Ti3-C0.15 refining master alloy. Basing on measurements performed by Krautkramer USLT2000 device with 1MHz ultrasound wave frequency it was stated that grain refinement reduces the attenuation coefficient by about 20-25%. However, the examined alloys can be still classified as the high-damping ones of attenuation greater than 150 dB/m.
The subject of this study is the presentation of relation between the degree of structure fineness and ultrasonic wave damping coefficient for the high-zinc aluminium alloys represented in this study by the sand mould cast alloy Al - 20 wt% Zn (AlZn20). The studied alloy was refined with a modifying (Al,Zn)-Ti3 ternary master alloy, introducing Ti in the amount of 400 pm into metal. Based on the analysis of the initial and modified alloy macrostructure images and ultrasonic testing, it was found that the addition of (Al,Zn)-Ti3 master alloy, alongside a significant fragmentation of grains, does not reduce the coefficient of ultrasonic waves with a frequency of 1 MHz.
The paper presents results of measuring thermal conductivity and heat capacity of bentonite foundry sand in temperature range ambient – 900 OC. During the experiments a technical purity Cu plate was cast into the green-sand moulds. Basing on measurements of the mould temperature field during the solidification of the casting, the temperature relationships of the measured properties were evaluated. It was confirmed that water vaporization strongly influences thermal conductivity of the moulding sand in the first period of the mould heating by the poured casting.