Rafał Michalik

Influence of casting conditions and alloy additives on the Zn40Al2Cu alloy structure

Zn-Al-Cu alloys are characterized by several advantageous properties that can include good castability, good tribological properties, and low energy value needed to form the product. In comparison to bronzes, Zn-Al-Cu alloys are characterized by a lower density. The purpose of this study was to determine the effect of casting conditions and the addition of silicon and rare earth elements on the structure of a Zn-40%Al alloy. The subjects of this examination were an unmodified alloy, an alloy with the addition of 1,5% Si, and an alloy with additions of 1,5%Si and rare earth elements. Samples were cast in sand and graphite molds. In order to determine the microstructure of the tested samples, metallographic examinations using a light microscope and a scanning electron microscope with energy dispersive spectroscopy (EDS) through an X-ray spectrometer were used.

Studies on the Corrosion Properties of High-Mn Austenitic Steels

Institute of Materials Science at Silesian University of Technology since 6 years conducts researches to learn about the new dedicated for automotive, railway and military industries. Some of these materials belong to the group of AHS steels, characterized by the twinning induced plasticity (TWIP) effect. It is a new type of steel possessing both a high strength and a great plastic elongation, and an ideal uniform work hardening behaviour. It is therefore a good candidate for deep drawing applications in the automobile and railway industries. In the paper the of the three grades of high-manganese steels of was studied in 3.5% NaCl solution and in an “acid rain” solution with pH=3.5 environments using polarization experiments. The results of corrosion tests and analysis of show that a higher polarisation resistance and lower values of corrosion current density are observed for all studied steels in 3.5% NaCl solution. Spontaneous passivation ability has been shown only for one grade of high-manganese steel in 3.5% NaCl.

Effect of Cooling Rate on the Porosity of the ZnAl22Cu3 Alloy

Zn-Al-Cu alloys are characterized by advantageous set of functional quality futures: tribological, strength, corrosion. They are used as an alternative material for bronze, cast iron and aluminum alloys in bearings and as a structural material. Properties of Zn-Al-Cu can be improved by partial or total replacement of copper with silicon and addition of rare - earth elements. Previous studies of the current authors have shown a significant effect of cooling rate on the structure of the ZnAl22Cu3 alloy. The presence of pores and significant differences in porosity between samples slowly and fast cooled has been found. The aim of this study was to determine the effect of cooling conditions on the pore formation in ZnAl22Cu3 alloy. The article presents the structure of the slowly and fast cooled alloy. Structural examinations were carried out on samples taken from the top, center and bottom of the ingot. In order to determine the microstructure metallographic tests were carried out using optical microscope and electron scanning microscope. Through EDS X-ray spectrometry quantitative analysis of characteristic microareas was performed as well. In order to assess the morphological characteristics of the pore a computer program Met-Ilo developed in the Department of Materials Science, Silesian University of Technology has been used. Changes of the volume fraction and the average area on a flat cross section in particular areas of the ingot were analyzed quantitatively.

Influence of Casting Conditions and Alloy Additions on the Zn22Al2Cu Structure

Zn-Al-Cu alloys are characterized by a number of beneficial properties that include good castability, good tribological properties and low energy input for forming the product. When compared to bronze, Zn-Al-Cu alloys have a lower density. Properties of Zn-Al-Cu can be improved by the partial or total replacement of copper with silicon and rare earth element additions. In the literature there are few studies on the effect of casting conditions and modifying the chemical composition through the introduction of alloy micro-additives on the alloy structure. The aim of this study was to determine the effect of casting conditions and silicon and rare earth element additions on the structure of Zn-22% Al-2%Cu alloy. The subjects examined were the unmodified alloy, the alloy with 1.5% Si and the alloy with 1.5% Si and rare earth elements (mich metal). Samples were cast in sand and graphite molds. The liquidus temperature for each of these examined samples was determined. Structure examinations were carried out in samples taken from the top, center and bottom of the ingot. In order to determine the microstructure of the examined structures metallographic examinations using an optical microscope and a scanning electron microscope with energy dispersive spectroscopy (EDS) capabilities, an X-ray microscope, was performed. Quantitive analysis on specific, characteristic microzones was performed based on the EDS X-ray spectroanalysis results.

Effect of Modification of Rare Earth Elements on the Morphology of Silicon Precipitates in the ZnAl22Cu3Si Alloy

Properties of the Zn-Al-Cu alloys can be improved by partial or total replacement of the copper with silicon. The previous studies of the current authors have shown that in alloys with silicon addition its precipitates are not evenly distributed, which can lead to uneven wear of parts made of the Zn-Al-Cu alloy. The study of phenomena occurring during the crystallization of the ZnAl22Cu3Si alloy with ATD methods have shown that silicon does not form compounds and solid solutions with Zn and Al. In the examined alloy silicon is released as the primary even before the actual solidification of dendrites. It is not possible to reduce the irregular distribution of precipitates through heat treatment. Therefore it is important to assure the uniform distribution of precipitates of silicon already on the crystallization stage, e.g. by addition of rare earth elements. The purpose of this study was to determine the effect of rare earth elements on the morphology of silicon precipitates in the ZnAl22Cu3Si alloy. The investigated material were alloys containing 22 wt% Al, 3 wt % Cu and 1.5 wt% Si (Zn-remaining). The samples have been taken from the top, middle and bottom of the ingot. In order to determine the morphological characteristics of silicon precipitates a computer program: Met-Ilo developed in the Department of Materials Science, Silesian University of Technology was used. Changes of the area fraction and shape of precipitates in particular areas of the ingot were the subject of analysis in this work.

Structure and Corrosion Resistance of Cast ZnAl40Cu2 Alloy

Zn-Al-Cu alloys are used as an alternative material for bronze, cast iron and aluminum alloys in bearings and as construction material. Advantageous results brings of their application for bearings exposed to high loads. One of the factors determining the possible applications of Zn-Al-Cu alloys is their resistance to electrochemical corrosion. In literature can be found information on the corrosion resistance of Zn-Al-Cu alloys. There have been no comprehensive studies on the influence of casting conditions and modifications of chemical composition on the structure and corrosion resistance. The purpose of the experiments was to determine the structure and corrosion resistance of cast Zn-40%Al-2%Cu alloy. The scope of the experiments included X-ray phase analysis, potentiodynamic and potentiostatic tests, surface condition examinations and alloy structure characterization both before and after corrosion. The Zn40Al2Cu alloy is characterized by a dendritic structure, consisting of solid solutions of Al, Zn-Al and Zn and the CuZn5 phase. A corrosive environment affects the structure of the subsurface zone of the Zn40Al2Cu alloy to a depth of 60 to 130 μm, where a decrease of zinc content and an increase of aluminum content are observed.

An Influence of the Self-Ageing on the Hardness and Corrosion Resistance of the ZnAl22Cu3 and ZnAl40Cu3 Alloys

The purpose of the examination was to determination of influence of self - ageing on the hardness and corrosion resistance of Zn - Al - Cu alloys. Subject of test were ZnAl22Cu3 and ZnAl40Cu3 alloys. The scope of examinations included: Brinell hardness tests and corrosion resistance tests. Tests were carried out just after heat treatment and after duration of 1, 2, 3, 4 and 5 months after heat treatment. The scope of corrosion test included galvanostatic and potentiodynamic tests. It was found, that natural ageing causes significant decrease of the hardness of ZnAl22Cu3 and ZnAl40Cu3 alloys after solution heat treatment. Carried out tests pointed out, that natural ageing significantly influences on corrosion resistance of ZnAl22Cu3 and ZnAl40Cu3 alloys. During ageing process, corrosion resistance is significantly changed. The high aluminum ZnAl 40Cu3 alloy as a higher hardness and higher corrosion resistance than ZnAl22Cu3 alloy

Structure and Hardness of the ZnAl40Cu(1-2)Ti(1-2) Alloys

The purpose of the examination was to determination of influence of microstructure and hardness of Zn-Al-Cu alloys with titanium addition. The subject of examination was were ZnAl40Cu2Ti, ZnAl40Cu1.5Ti1.5 and ZnAl40Ti2Cu alloys. The scope of test included Brinell hardness tests, tests on optical microscope, tests on scanning microscope and X-ray microanalysis. It was found that tested ZnAl40Cu(1-2)Ti(1-2) alloys are characterized by homogeneous, fine- grained structure. Carried out tests pointed out, that addition of titanium to ZnAl40Cu(1-2)Ti(1-2) alloy influences on hardness increasing. It was also found, that the titanium forms Ti-Al precipitates in ZnAl40Cu(1-2)Ti(1-2) alloys and does not take part in solution strengthening process.

Influence of Strain Rate Effects on the Structure and Mechanical Properties of the Fully Austenitic High Mn Steels under Dynamic Impact Deformation

The article presents the dynamic mechanical properties of two types of high manganese austenitic steels. The investigation were carried out for the wide range of strain rates from 1×10-4s-1 up to 4×103s-1 using servo-hydraulic testing machine and Hopkinson bar for the quasi-static and dynamic loading regime, respectively. The mechanical properties at different strain rates as well as the SEA indicator calculated were carried out on the base of the results of impact tests. In the next step, the microstructure of the steel after different deformation rate was observed and analyzed by light microscope in order to disclose a TWIP effect.

The Influence of Molding Parameters on the Structure of the ZnAl40Cu2Ti Alloy

The aim of this study was to determine the influence of casting technology on the structure of the ZnAl40Cu2Ti alloy. The scope of the examination included Brinell hardness tests and tests on optical microscopy, scanning electronic microscope test and X-ray microanalysis. The tests showed that, depending on the casting technology can be obtained different ZnAl40Cu2Ti alloy structure, characterized by different chemical composition in microareas. It has been pointed out that in order to get ZnAl40Cu2Ti alloy modification of Zn-Al-Cu alloy used technology casting is necessary.