H. Woźnica

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.

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.

Influence of Heat Treatment on Corrosion Resistance of the ZnAl22Cu3 Alloy

Zn-Al-Cu type alloys are characterized by a number of advantageous properties which include: good castability, good tribological properties, low energy value needed for forming of the product. As compared to bronze, Al-Zn-Cu alloys are characterized by a lower density. Improved properties of Zn-Al alloys can be obtained by addition of copper and silicon. Advantageous results can also be obtained by heat treatment. There is an extensive literature on the effect of heat treatment upon the structure of Al-Zn-Cu alloys. However, few articles discuss the effect of heat treatment on the corrosion resistance of alloys. The purpose of this examination was to determine the effect of heat treatment on corrosion resistance of ZnAl22Cu3 alloy. The unmodified alloy containing 22% Al mass. and 3%. Cu (Zn - remain) was subjected to the examinations. Tested alloys underwent the following operations: soaking at the temperature of 185°C for 10 hours with cooling in water, soaking at the temperature of 380°C for 10 hours with cooling in water and soaking at the temperature of 380°C for 10 hours with subsequent soaking at the temperature of 170°C with cooling in water. Potentiodynamic and potentiostatic examinations in a solution of acid rain with pH = 3.5 were carried out. Then the tests were followed by examination of the corroded sample surface.The carried out examinations showed a decrease in corrosion resistance after heat treatment at the temperature of 380°C and a slight increase after heat treatment at the temperature of 185°C.