Internal casting defects that are detected by radiography may also be detected by ultrasonic method. Ultrasonic testing allows investigation of the cross-sectional area of a casting, it is considered to be a volumetric inspection method. The high frequency acoustic energy travels through the casting until it hits the opposite surface or an interface or defect. The interface or defect reflects portions of the energy, which are collected in a receiving unit and displayed for the analyst to view. The pattern of the energy deflection can indicate internal defect. Ultrasonic casting testing is very complicated in practice. The complications are mainly due to the coarse-grain structure of the casting that causes a high ultrasound attenuation. High attenuation then makes it impossible to test the entire volume of material. This article is focused on measurement of attenuation, the effect of probe frequency on attenuation and testing results.
Nil strength temperature of 1062°C and nil ductility temperature of 1040°C were experimentally set for CuFe2 alloy. The highest formability at approx. 1020°C is unusable due to massive grain coarsening. The local minimum of ductility around the temperature 910°C is probably due to minor formation of γ-iron. In the forming temperatures interval 650-950°C and strain rate 0.1-10 s–1 the flow stress curves were obtained and after their analysis hot deformation activation energy of 380 kJ·mol–1 was achieved. Peak stress and corresponding peak strain values were mathematically described with good accuracy by equations depending on Zener-Hollomon parameter.
The Ca50Mg20Zn12Cu18 was assessed with different methods in order to characterize its basic characteristics, and to determine whether the amorphous alloy of such composition would be applicable as an implant material. The XRD analysis was conducted to conclude the structure of the initial material. The Ca50Mg20Zn12Cu18 ingot sample demonstrates crystalline structure containing two main intermetallic phases, however as-cast plates show features of an amorphous material, revealing the characteristic amorphous halo on the x-ray patterns. It was confirmed by the scanning electron microscopy method and fracture images revealing chevron pattern morphology with shell type fracture. Corrosion resistance, was studied using the potentiostatic analysis. The amorphous samples show higher resistance than the crystalline one. Post corrosion surface of the Ca50Mg20Zn12Cu18 alloy exhibits high concentration of magnesium and calcium hydroxides, forming the globular structures in large aggregates of spherical units.
The article deals with ultrasonic testing possibilities of the copper alloy centrifugal casts. It focused on the problems that arise when testing of castings is made of non-ferrous materials. Most common types of casting defects is dedicated in theoretical introduction of article. Ultrasonic testing technique by conventional ultrasound system is described in the theoretical part too. Practical ultrasonic testing of centrifugal copper alloy cast - brass is in experimental part. The experimental sample was part of centrifugally cast brass ring with dimensions of Ø1200x34 mm. The influence of microstructure on ultrasonic attenuation and limitations in testing due to attenuation is describes in experimental part. Conventional direct single element contact ultrasound probe with frequencies of 5 MHz, 3.5 MHz and 2 MHz were used for all experimental measurements. The results of experimental part of article are recommendations for selecting equipment and accessories for casting testing made of non-ferrous metals.