Odlewanie precyzyjne stopów magnezu o podwyższonych właściwościach

W pracy przedstawiono wybrane aspekty technologii precyzyjnego odlewania stopów magnezu o podwyższonych właściwościach w formach ceramicznych. Przedstawione wyniki badań dotyczą możliwości otrzymywania odlewów ze stopów magnezu o podwyższonych właściwościach mechanicznych i tribologicznych w technologii wytapianych modeli. Poprawę właściwości stopów magnezu uzyskano w wyniku opracowania składu chemicznego nowych stopów magnezu w oparciu o znormalizowane stopy AM60 i AZ91 oraz parametrów ich krystalizacji stosując intensywne studzenie form ceramicznych. W pracy przedstawiono wpływ dodatków chromu lub/i wanadu na mikrostrukturę, charakterystyczne krzywe ATD oraz właściwości mechaniczne oraz tribologiczne badanych stopów. Dodatkowo przedstawiono wyniki badań dotyczące opracowania innowacyjnej technologii nanoszenia inhibitorów na wewnętrzne ściany formy ceramicznej, których zastosowanie pozwoliło na wykonanie odlewów pozbawionych wad powierzchniowych (...).The monograph, based on the author’s original research and ideas, is his contribution to the discipline of Mechanical Engineering. The monograph presents selected aspects of the precision casting technology applied for magnesium alloys with elevated mechanical and tribological properties made in ceramic moulds. The discussed test results concern the possibility of obtaining casts from magnesium alloys with elevated properties in the investment casting technology. An improvement of the magnesium alloy properties was achieved through modification of the chemical composition of normalized alloys AM60 and AZ91 as well as elaboration and application of the technology of intensive cooling of the ceramic moulds. The study demonstrates the effect of chromium and/or vanadium additions on the microstructure, characteristic ATD curves as well as mechanical and tribological properties of the examined alloys. Additionally, the paper presents the test results referring to the elaboration of a technology of preparing ceramic moulds with inhibitors, the application of which made it possible to produce casts without surface defects (...)

Wpływ dodatków stopowych Cr i V na mikrostrukturę i właściwości mechaniczne stopu AM60

The paper presents the results of the investigation of the effect of Cr and/or V alloy additions on the microstructure and mechanical properties of the magnesium AM60 alloy. The examinations are performed within the frames of a project aiming at the elaboration of an experimental and industrial technology of producing constructively complex elements of machines and devices made of magnesium alloys with the method of investment casting. It has been proven that small numbers of Cr and V alloy additions improve the strength properties: Rm, A%, and the hardness HB of the obtained casts. The experimental casts were made in ceramic molds.W pracy przedstawiono wyniki badań wpływu dodatków stopowych Cr i/lub V na mikrostrukturę oraz właściwości mechaniczne stopu magnezu AM60. Badania prowadzone są w ramach projektu, którego celem jest opracowanie technologii doświadczalnej i przemysłowej wytwarzania złożonych konstrukcyjnie elementów maszyn i urządzeń ze stopów magnezu metoda wytapianych modeli. Wykazano, że niewielkie ilości dodatków stopowych Cr i V poprawiają właściwości wytrzymałościowe: Rm, A%, oraz twardość HB otrzymanych odlewów. Odlewy doświadczalne wykonano w formach ceramicznych

Analysis of the crystallization of AZ91 alloy by thermal and derivative analysis method intensively cooled in ceramic shell.

The work presents the test result of the influence of cooling rate on the microstructure of AZ91 alloy, Vickers micro-hardness and Brinell hardness. Studies cooling and crystallization of AZ91 alloy was cast into the ceramic shells pre-heated to 180 ° C and then air-cooled at ambient temperature or intensively super cooled in the liquid coolant. The TDA method was applied to record and characterize the thermal effect resulting from the phase transformations occurring during the crystallization of AZ91 alloy. The kinetics and dynamics of the thermal processes of crystallization of AZ91 alloy in the ceramic shells were determined. Metallographic tests were performed with the use of an optical microscope. A comparison of these test results with the thermal effect recorded by way of the TDA method was made. Influence of cooling rate of AZ91 on HV0, 01 micro-hardness and Brinell hardness alloy was examined

Analiza krystalizacji stopów AM60 i AZ91 w formie ceramicznej metoda analizy termiczno-derywacyjnej (ATD)

The work presents the test results of the crystallisation and cooling of magnesium alloys: AM60 and AZ91, with the use of the TDA method. The tested alloys were cast into ceramic shells heated up to 180 C, produced according to the technology of the shell production in the investment casting method. The TDA method was applied to record and characterize the thermal effect resulting from the phase transformations occurring during the crystallisation of magnesium alloys. The kinetics and dynamics of the thermal processes of the crystallisation of AM60 and AZ91 in the ceramic shells were determined. Metallographic tests were performed with the use of an optical microscope as well as scanning microscopy, together with the EDS chemical analysis of the phases present in the tested casts. A comparison of these test results with the thermal effect recorded by way of the TDA method was made.W pracy przedstawiono wyniki badań krystalizacji i stygnięcia stopów magnezu: AM60 i AZ91 przy użyciu metody ATD. Badane stopy zalewano do form ceramicznych podgrzanych do temperatury 180C, wykonanych zgodnie z technologią wytwarzania form w metodzie traconych modeli. Przy pomocy metody ATD zarejestrowano i wyznaczono charakterystyczne efekty cieplne wynikające z przemian fazowych zachodzących podczas krystalizacji badanych stopów magnezu. Określono kinetykę i dynamikę procesów cieplnych krystalizacji stopów AM60 i AZ91 w formach ceramicznych. Przeprowadzono badania metalograficzne przy pomocy mikroskopu optycznego oraz mikroskopii skaningowej wraz z analizą chemiczną EDS występujących faz w badanych odlewach. Porównano wyniki tych badań z efektami cieplnymi zarejestrowanymi metodą AT

Standards of nasal provocation tests

The nasal allergen provocation test (NAPT) plays an important role in diagnosis of allergy. It is based on the natural reaction of the nasal mucosa after application of tested substances on their surface. Nasal challenges are divided into specific (allergenic) and non-specific. Typical clinical symptoms depend on the immunological reaction: sneezing, itching, rhinorrhea and nasal blockage. Eosinophilic mucosal infiltration is observed in the late phase reaction. Typically the result of nasal challenge should be assessed by the physician and patient. The immunological reaction, especially the level of particular allergenic mediators, could also be investigated. Some objective methods for final assessment of the results are recommended. There is some information about non-specific nasal provocation with aspirin and occupational diseases in the pape

A representative ex-situ fretting wear investigation of orthodontic arch-wire/bracket contacts

International audienc

Effect of Gadolinium on the Microstructure of Magnesium Alloy AZ91

The paper presents the results of research related to the possibility of inoculation of the AZ91 magnesium alloy casted into ceramic moulds by gadolinium. Effects of gadolinium content (0.1–0.6 wt%) on microstructure of the AZ91 alloy under as-cast state were investigated. The influence of the inoculator on the formation of the microstructure investigated by means of the thermal and derivative analysis by analysing the thermal effects arising during the alloy crystallization resulting from the phases formed. The degree of fragmentation of the microstructure of the tested alloys was assessed by means of the light microscopy studies and an image analysis with statistical analysis was performed. Conducted analyses have aimed at examining on the effect of inoculation of the gadolinium on the differences between the grain diameters and average size of each type of grain by way of measuring their perimeters of all phases, preliminary αMg and eutectics αMg+γ(Mg17Al12) in the prepared examined material

Effect of Degassing Parameters on Mechanical Properties of EN AC-46000 Gravity Die Castings

The article is devoted to the optimization of the degassing parameters of the AlSi9Cu3(Fe) alloy. The alloy was degassed with a solid degasser (Ecosal) and nitrogen or argon. The variable parameters were time and type of degasser. The test castings were made in permanent molds with an internal diameter of 25 mm and a length of 150 mm. The effect of the degassing time and the amount of degasser on the mechanical properties, as well as the hydrogen content and density index were investigated. The ALU SPEED TESTER developed by FMA was used to test the hydrogen content and the density index. Magmasoft software was used to design the geometry of the test castings. A significant effect of the solid degasser and degassing time on both the density index and the hydrogen content was demonstrated. Replacing nitrogen with argon did not bring any significant improvement in the above-mentioned parameters. The effect of degassing parameters on the mechanical properties of the EN AC-46000 alloy was much less significant, but was still visible. The optimal degassing parameters needed to obtain the highest strength parameters of the EN AC-46000 gravity die castings were determined

Unlocking the Potential of Biomass Fly Ash: Exploring Its Application in Geopolymeric Materials and a Comparative Case Study of BFA-Based Geopolymeric Concrete against Conventional Concrete

The production of conventional cement involves high energy consumption and the release of substantial amounts of carbon dioxide (CO2), exacerbating climate change. Additionally, the extraction of raw materials, such as limestone and clay, leads to habitat destruction and biodiversity loss. Geopolymer technology offers a promising alternative to conventional cement by utilizing industrial byproducts and significantly reducing carbon emissions. This paper analyzes the utilization of biomass fly ash (BFA) in the formation of geopolymer concrete and compares its carbon and cost impacts to those of conventional concrete. The previous analysis shows great potential for geopolymers to reduce the climate change impact of cement production. The results of this analysis indicate a significant disparity in the computed financial and sustainability costs associated with geopolymers. Researchers have shown that geopolymers may help mitigate the effects of cement manufacturing on the environment. These geopolymers are predicted to reduce green gas emissions by 40–80%. They also show that those advantages can be realized with the best possible feedstock source and the cheapest possible conveyance. Furthermore, our case study on CO2 emission and cost calculation for BFA-based geopolymer and conventional concrete shows that geopolymer concrete preparation emits 56% less CO2 than conventional concrete while costing 32.4% less per ton

Determination of the Thermal Parameters of Geopolymers Modified with Iron Powder

The paper presents the results of research concerning the influence of a metallic micromaterial on the thermal conductivity λ, specific heat Cp, and thermal diffusivity a of modified geopolymers. Iron oxide in the form of powder with an average granulation of 10 μm was used as the geopolymer-modifying material. The research concerned geopolymer composite samples with metakaolin (activated with potassium silicate) and the addition of iron in amounts ranging from 0.5% to 2.5% in relation to the weight of the metakaolin. Additionally, the samples were modified with sand and fireclay in two different amounts—1:1 and 1:1.2 in relation to the metakaolin. The addition of fireclay caused a decrease in the thermal conductivity of the composites by 30% when compared to the samples with the addition of sand. The lowest value of the thermal conductivity coefficient λ was obtained for the geopolymer with metakaolin and fireclay. When the ratio of these components in the composite was 1:1, the value of thermal conductivity was equal to 0.6413 W/(m·K), while in the case of their ratio being 1:1.2, it was equal to 0.6456 W/(m·K). In the samples containing fireclay, no significant influence of the added iron on the values of thermal conductivity was noticed. In the case of the geopolymer with sand, the effect was noticeable, and it was most visible in the samples containing metakaolin and sand in the ratio of 1:1.2. It was noticed that with an increase in the addition of Fe, the thermal conductivity of the composite increased