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Content available remote Effect of heat treatment on mechanical properties of magnesium alloy AZ61
The contribution is focussed on the assessment of the influence of a heat treatment of magnesium alloy AZ61 on its mechanical properties. The magnesium alloy AZ61 was manufactured by squeeze casting method using alternative two-stage casting. Metallographic analysis was made by means of light and electron microscopy utilising also the possibility of local chemical analyses. The assessment of the influence of a heat treatment on mechanical properties of AZ61 magnesium alloy was performed by means of tensile tests on specimens of rational geometry. The heat treatment of the bars was performed at the temperature of 380 °C and with dwell from 1 to 16 hours to result in T4 (solution annealed) state. Basic stress and strain characteristics were assessed from the results of the tensile tests. It follows from the experimental results that the tensile strength and deformation characteristics grow even after only 1 hour of dwell at the temperature of 380 °C. Maximum values of tensile strength and deformation characteristics were achieved after 6 hour dwell at the temperature. It was confirmed by the metallographic analysis of the test specimens that there occurs the dissolution of the hard and brittle Mg17Al12 intermetallic phase. It was found by the local chemical analysis that the decrease in micro-heterogeneity of the ä solid solution takes place here at the same time. The increase in the tensile strength and deformation characteristics is caused by the dissolution of the hard and brittle intermetallic phase and by the decrease in heterogeneity of the matrix.
Content available remote Únavové vlastnosti hořčíkové slitiny AZ31
Magnesium alloys are desirable for their low densities and high specific strength to structural use. That is why determining of fatigue properties magnesium alloys are desirable. Here was examined fatigue properties on squeeze casting magnesium alloy AZ31 with 0.5 wt% Ca.
The paper focuses on problems of optimizing the forming temperature of grade 100CrMnSi6-4 bearing steel under partial heating. In order to assess its formability, tensile tests at elevated temperatures ranging from 100 to 800 °C were carried out. Tensile diagrams revealed jump changes of mechanical properties in the brittle region under blue heat and in the region of phase transformations. Experimental examination was then concentrated on assessing the plastic deformation capability of the material under pressure at elevated temperatures, by means of the upsetting test. Another goal of the paper consisted in comparing the two experimental methods chosen for establishing the optimum temperatures of forming grade 100CrMnSi6-4 bearing steels at elevated temperatures. To have a complex assessment of the experimental material the structure and phase analyses of the bearing steel were performed in dependence on heating temperature.
Content available remote Influence of homogenizing on structure and mechanical properties of AZ91 alloy
This paper deals with the influence of homogenizing on mechanical properties of magnesium alloy AZ91. The experimental material was made squeeze casting. Results of tensil test of the sample without heat treatment and samples with homogenizing (405°C/5, 10, 15 and 24 hours) were compared. To study of microstructure light microscopy was used.
The forming process is associated with the plastic deformation capability of materials. The formability of metals and alloys is influenced by physical-metallurgical properties of material and by external forming conditions, forming temperature in particular. A kind of borderline for the division of forming is the recrystallization temperature, according to which forming is divided into cold forming, partially hot forming and hot forming. The paper is concerned with problems of optimizing the temperature of forming grade 100CrMo7-3 bearing steel under partial heating. Experimental establishment of the optimum range of forming temperatures was based on the results of tensile testing at elevated temperatures from 100 to 800 °C. Experimental verification of the behaviour of bearing steel under pressure was conducted via the upsetting test at elevated temperatures. The experimental part of the work is also concerned with the analysis of phase composition of grade 100CrMo7-3 bearing steel using computer simulation, and by the verification of simulation via metallographic evaluation.
This article describes the influences of cooling speed and head treatment on the microstructure and mechanical properties of aluminium alloy AlSi7Mg0,6 (trade description – Anticorodal 72). Results of tensile test (strength, yield strength, ductility, etc. ) to both method heat processing (T6 and T 64).
Content available remote Estimation of tolerance bands of S-N curve
A precise determination of tolerance bands of S-N curves is very difficult problem; therefore simple approximate constructions of these bands are often used. Castillo et al. suggested sophisticated and at the same time easy procedure for their estimation which, however, is based on a special type of regression function for describing S-N curve. This type of regression function called the Castillo function is suitable only for high-cycle fatigue region close to fatigue limit. The paper focuses on the Kohout and Vechet function with wider usability applied in the Castillo procedure.
Content available remote O potrzebie wykorzystania metodologii nauk przyrodniczych w procesie transformacji
Artykuł dotyczy metodologicznej strony nauk ekonomicznych. Przedstawiono w nim argumenty na rzecz wykorzystywania metodologii nauk przyrodniczych do poznawania i opisywania zjawisk do zastosowania na etapie transformacji systemowej w krajach Europy Środkowo-Wschodniej.
The article refers to the methodological side of economic sciences. The author introduced possibility using the methodology of nature sciences for recognition and description of systems tranformation in Middle - Eastern Europe.
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