Micro-defects detection in solidified castings of aluminum alloy has always been a hot topic, and the method employed is mainly depends upon the size and shape of the specimens. In present paper, the amount and distribution characters of micro-defects in a series of 2219 aluminum alloy ingot, with diameters of φ1380 mm, φ1250 mm, φ1000 mm, φ850 mm and φ630 mm, prepared by direct chill casting were investigated by means of metallographic, respectively. Samples were cut along the radius direction from slices in the steady casting stage. The result reveals that typical micro-defects are consist of inclusions, porosity and shrinkage under optical microscope, and the total amount of micro-defect per unit area in an ingot slightly decreased with the increase of its diameter. Meanwhile, defects were classified into 2 types according to its size, the results suggesting that defects greater than 40 μm account for the largest proportion among the counted two kinds of defects. Moreover, the distribution of defects greater than 40 μm along the radial direction was detected, its amount increases as its distance from the side, indicating that the micro-defects greater than 40 μm distributed the most in the center zone of ingots and the larger the ingot diameter, the more obvious the tendency was.
ABSTRACT:
The main goal of this publication is to familiarize western numismatists with the current trends and findings in the research on medieval payment ingots (grivnas) in Eastern Europe. The author presents up-to-date chronological classification of silver payment ingots, shortly describes their basic types and gives the basic list of classic and modern works in this field.
The article presents the results of research concerning AlCu4MgSi alloy ingots produced using horizontal continuous casting process under variable conditions of casting speed and cooling liquid flow through the crystallizer. The mechanical properties and structure of the obtained ingots were correlated with the process parameters. On the basis of the obtained results, it has been shown that depending on the cooling rate and the intensity of convection during solidification, significant differences in the mechanical properties and structure and of the ingots can occur. The research has shown that, as the casting speed and the flow rate of the cooling liquid increase, the hardness of the test samples decreases, while their elongation increases, which is related to the increase of the average grain size. Also, the morphology of the intermetallic phases precipitations lattice, as well as the centerline porosity and dendrite expansion, significantly affect the tensile strength and fracture mechanism of the tested ingots.
Currently there is a constant development in the field of aluminium alloys engineering. This results from, i.a., better understanding of the
mechanisms that direct strengthening of these alloys and the role of microalloying. Now it is microalloying in aluminum alloys that is
receiving a lot of attention. It affects substantially the macro- and microstructure and kinetics of phase transformation influencing the
properties during production and its exploitation. 7xxx series aluminum alloys, based on the Al-Zn-Mg-Cu system, are high-strength
alloys, moreover, the presence of Zr and Sr further increases their strength and improves resistance to cracking.
This study aims to present the changes of the properties, depending on the alloy chemical composition and the macro- and microstructure.
Therefore, the characteristics in the field of hardness, tensile strength, yield strength and elongation are shown on selected examples.
Observations were made on ingot samples obtained by semi-continuous casting, in the homogenized state.
Samples were prepared from aluminum alloys in accordance with PN-EN 573-3: 2013. The advantage of Al-Zn-Mg-Cu alloys are
undoubtedly good strength, Light-weight and resistance to corrosion. As widening of the already published studies it is sought to
demonstrate the repeatability of the physical parameters in the whole volume of the sample.
The paper consists the problem of developing a scientific toolkit allowing to predict the thermal state of the ingot during its formation in all elements of the casting and rolling complex, between the crystallizer of the continuous casting machine and exit from the furnace. As the toolkit for the decision making task the predictive mathematical model of the ingot temperature field is proposed. Displacement between the various elements of the CRC is accounted for by changing the boundary conditions. Mass-average enthalpy is proposed as a characteristic of ingot cross-section temperature state. The next methods of solving a number of important problems with the use of medium mass enthalpy are developed: determination of the necessary heat capacity of ingots after the continuous casting machine for direct rolling without heating; determination of the rational time of alignment of the temperature field of ingots having sufficient heat capacity for rolling after casting; determination of the total amount of heat (heat capacity) required to supply the metal for heating ingots that have insufficient amount of internal heat.
Experimental observations of the steel morphology as well as measurements of the solutes concentration in the macro-scale were made on the basis of the vertical cut at the mid-depth of the 15-tons steel forging ingot serially produced in one of the steel plant in Poland. Experimental observations of the morphology accompanied by the measurements of the Peclet Number were also made on the cross-section of the continuously cast brass ingots serially produced in the copper / brass industry in Poland. The performed measurements allowed to work out some maps of the alloying elements segregation for the longitudinal section of the steel static ingot and a Growth Law for the columnar grains formation in the brass ingots. The marginal stability criterion has been applied to the last mentioned development / description. Some suggestions for the micro-segregation measurement mode in the columnar structure are derived.