Application of the Hydraulic Diameter of Interdendritic Space for Calculating the Ultimate Tensile Strength of Gray Cast Iron

A comparative analysis of methods for estimating the gray cast iron ultimate tensile strength σu by the hydraulic diameter of interdendritic space DHydIP and the volume fraction of primary austenite dendrites fdc is performed. Almost the same accuracy of cast iron castings σu estimation according to both these parameters DHydIP and fdc of the primary microstructure is shown.

Creation of AlSi12 Alloy Coating by Centrifugal Induction Surfacing with the Addition of Low-Melting Metals

This paper investigates the structure and mechanical characteristics of a coating based on an AlSi12 alloy, obtained by centrifugal induction surfacing as an alternative to a bronze sliding bearing. To provide for the adhesion of an aluminum layer to the inner surface of a steel bearing housing, a sublayer of low-melting metals was formed, while the formation of the main layer and the sublayer was done in a single processing cycle. The low-melting metals had higher density, which ensured that the sublayer was created at the interface with the steel bearing housing under the action of centrifugal forces. It is shown that the low-melting sublayer forms a strong bond both with the aluminum alloy and with the steel base. Lead and tin are used as low-melting additives. It has been established that lead or tin used in a sublayer are indirectly involved in the structural formation of boundary layers of steel and aluminum claddings, acting as a medium for diffuse mass transfer. Thus, lead is not included in the composition of the main coating and does not change the chemical composition of the aluminum layer. After the addition of tin, the aluminum develops a dendritic structure, with tin captured in the interdendritic space. In this case, the deposited layer is saturated with iron with the formation of intermetallic (Fe, Al, Si) compounds, both at the interface and in the coating volume. This paper offers an explanation of the mechanism through which Pb and Sn act on the structure formation of the coating, and on the boundary layer of the steel bearing housing. Tribological tests have shown that the resulting materials are a promising option for plain bearings and highly competitive with the CuSn10P bronze.

Microstructure and Mechanical Properties of the Alloy Mg61Cu28Gd11 in Submicrovolumes

We studied the microstructure and nanomechanical properties of cast samples of the alloy Mg61Cu28Gd11, obtained by the original method. The alloy Mg61Cu28Cd11 is distinguished by a particularly high glass transition property. In this study samples with a diameter of 16 mm were obtained an inert atmosphere with a cooling rate of 1K/s. Liquid alloy Mg61Cu28Gd11 before crystallization was heated to 780 °C. It was previously installed that, with such heating, irreversible structural changes occur in the melt, which increase the tendency of the metal to glass transition. A metallographic study of the microstructure was performed using a scanning electron microscope and EDS-analysis. Nanohardness HV and Young's modulus E Mg2CuCd and Mg2Cu were measured using the nanoindentation method.The microstructure of the Mg61Cu28Cd11 alloy in the cast state consists mainly of Mg2Cu dendrites; the interdendritic space is represented by the Mg2CuCd phase. The presence of exogenous nonmetallic inclusions of a complex composition CdO + CuO + MgO was also established by the method of micro X-ray spectral analysis.Analysis of the measurement data of HV(GPa), E (GPa) gave a conclusion about the same degree of homogeneity of the mechanical properties of dendrites and interdendritic space.

PROCUREMENT OF FERROTITIAN FROM METAL INDUSTRY WASTE BY METHOD OF ALUMOTHERMAL SYNTHESIS

Researches of procurement of ferrotitanium of Fti25 brand from waste products by method of aluminothermic synthesis are conducted. The thermodynamic analysis revealed that differences in using oxide of iron (Fe2O3) and iron cinder (Fe3O4) are subtle and it is confirmed by the experimental results. According to an elemental analysis, when using an iron cinder, the received alloy contains 18, 0–21,5 titanium and 68–73% of iron. Research of structure showed that at a crystallization of the received alloy two main phases are formed: exuberant, which is presented by dendrites with pronounced borders length of an axis of first order of a dendrite was about 250 microns and having the eutectic structure, is allocated in interdendritic space. It is established that the increase in a mass fraction of oxide of calcium in fusion mixture there is an increase in dispersion of structural components and some sferoidization, transition of an excess phase to globular.

Modification of the Al0.9Zn0.05Sn0.05 Alloy Microstructure by Cold Working and Chemical Composition

ABSTRACTAluminum alloys have increased their use due to the properties such as low density, resistance to corrosion under environmental conditions and mechanical properties. In this work, the alloying elements are immiscible promoting dendrites formation with different phases attributed to zinc and tin. The applied mechanical stresses promoted the modification of the dendrite sizes (interdendritic space) as well as pore sizes and shapes. The microhardness decreased in the ternary Al-Zn-Sn alloy with a subsequent increase caused by microstructural changes after cold work. By XPS, the metallic elements were detected with an aluminum oxide layer.

The Study of the Dissolution AlZr2 Ligatures in the Liquid Alloy AlMg6Mn1

We studied the dissolution of zirconium in the molten alloy AlMg6Mn1. Zirconium is introduced into the melt in the form of the ligature AlZr2. It is established that during 10 minutes at 750 °C complete Zr dissolution occurs. The study of the structure and phase composition of the samples allowed setting the dendrite structure of the samples; presence of clusters of magnesium, manganese, iron and silicon in the interdendritic space. Zirconium is injected into the melt in a stable particulate form (D023) Al3Zr phase is uniformly distributed in grains α - Al as a metastable (L12) Al3Zr phase. After some time, increasing of the density distribution of the metastable (L12) Al3Zr in the aluminum matrix phase is detected in the selected samples after 10 and 60 minutes after the introduction of zirconium. It has been established that after some time, an increase of the aluminum lattice parameter occurs in the samples selected after the addition ligature of zirconium.

Tin and Nickel Influence on the Structure and Properties of the Leaded Bronze Obtained by Means of the Centrifugal Casting

The effect of tin and nickel on the structure and properties of the leaded bronze obtained by means of the centrifugal casting has been studied. Regularities of change of strength properties and ductility explain the features of the structure formation under the influence of nickel and tin. The paper demonstrates that introduction of nickel promotes a uniform distribution of the plate-shaped lead in the interdendritic space. Introduction of tin sufficient for the formation of eutectoid results in a uniform and compact arrangement of lead in the intergranular space. Complex alloying with nickel and tin contributes to strength characteristics increase.

Solidification Behavior and Mechanical Properties of Al-Si-Mg Alloy with Ti Addition

The solidification behavior, microstructural evolution and mechanical properties of Al-Si-Mg foundry alloy with different Ti additions were investigated in the present study. The solidification behavior of those A357 alloys was analyzed through thermal analysis. The microstructures were examined by optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results showed that the addition of Ti could refine grains of A357 as-cast alloy due to a good restriction on the grain growth, but Ti could not refine secondary dendrite arm spacing (SDAS), thus mechanical properties of the A357 as-cast alloy did not improved significantly. After T6 heat treatment, the microstructure with α-Al dendrites with the Al-Si eutectics at interdendritic space was replaced by a homogeneous α-Al matrix with a nonuniform dispersion of discrete, spheroidizing and coarse silicon particles. Hence, compared with the as-cast alloys, both of the strength and ductility of the T6 treated alloys are significantly improved, and an optimal combination of strength and elongation of the A357 alloy can be achieved by the 0.8 wt.% Ti addition after T6 heat treatment.

The Structure and Corrosion Resistance of the Coatings Obtained by Non-Vacuum Electron Beam Cladding of the Ti-Nb Powder Mixture on a Titanium Substrates

In this study Ti-Nb coatings formed on the surfaces of cp-titanium plates by electron beam cladding were investigated. It was found that the coatings were characterized by a dendrite structure and a quenched structure was observed in the interdendritic space. The energy dispersive X-ray analysis revealed some differences between the elemental composition of different areas corresponding to dendritic crystals and the space between them. The corrosion resistance of the Ti-Nb alloy obtained on the titanium surface in the concentrated nitric acid was almost 8 times higher than the cp-titanium corrosion resistance.

Fabrication of Multi-Layered Ti-Ta-Zr Coatings by Non-Vacuum Electron Beam Cladding

In this study Ti-Ta-Zr coatings fabricated on VT1-0 titanium substrates by non-vacuum electron beam cladding in one, two and three passes were investigated. Coatings were characterized by a high quality; such defects as cracks and voids were not observed. The structure of coating was commonly dendritic. The acicular structure in the one-layered coating and in the first layer of multilayered coatings was revealed by using scanning electron microscopy (SEM). The results of the energy dispersive X-ray (EDX) analysis indicated the presence of tantalum and zirconium segregations in dendrite arms and in the space between them. It was found that dendritic branches contained the maximum of tantalum while an increased amount of zirconium was concentrated in the interdendritic space. The maximum concentration of alloying elements (56.87 wt. % Ta and 22.22 wt. % Zr) was obtained in the layer cladded in the third pass of an electron beam. The microhardness of Ti-Ta-Zr layers rose from 4.5 GPa to 6 GPa with an increase in .the percentage of alloying elements