Metallurgical and Materials Data

Metal ceramic joining with active filler metal in dental practice

Karlo Raic — Mon, 15 Jul 2024 00:00:00 +0000

This paper examines the phenomena that arise at the interface between ceramics and active filler metal during the metal-ceramics bonding process in dental practice. It focuses on three interrelated sub-processes: the wetting of the ceramic surface, the chemical interactions at the interface, and the diffusion across the moving interface. Additionally, the study explores the grain boundary grooves on the ceramic surface, highlighting their role as catalytic surface phenomena.

Following a brief overview of dental metals and bioceramics, the composition and properties of the brazing alloys used in dental practice are presented and explained in detail.

Mechanical Properties of Mullite Investigated by Nanoindentation

Jovana Ružić, Jelena Maletaškić, Željko Radovanović, Svetlana Ilić — Mon, 15 Jul 2024 00:00:00 +0000

The mechanical behavior of sintered mullite material was studied using nanoindentation tests. Mullite compact was obtained by cold pressing sol-gel synthesized mullite precursor powder and sintering at 1550 °C. Analysis of the microstructural parameters and phase composition was done by XRD (X-ray diffraction) and SEM-EDS (scanning electron microscopy with energy dispersive X-ray spectrometry). A Berkovich indenter was employed for nanoindentation measurements at various loads (1000-9000 µN). After each test, in situ SPM (scanning probe microscopy) imaging was performed. The XRD pattern of sintered mullite displayed peaks of mullite (93.3%) and corundum (6.7%). Results revealed average values of hardness and elastic modulus of sintered mullite as 15.55 GPa and 174.37 GPa, respectively. Moreover, nanoindentation results indicated that mullite follows the Hall-Petch hardening relation due to the presence of grains with a size range of 0.2-2 µm. Indentation in areas with smaller grains exhibits higher hardness values. Post-test SPM images disclosed the presence of pile-ups around the indents, which were formed under loads higher than 3000 µN.

Non-destructive Evaluation of Cavitation Erosion Behavior of Alumina-based Ceramic Samples

Ana Alil, Sanja Martinović, Tatjana Volkov-Husović — Mon, 15 Jul 2024 00:00:00 +0000

Numerous industrial parts, devices, and processes are designed to withstand the conditions that lead to cavitation erosion. Metallic, ceramic, and composite materials used for these conditions must achieve specific mechanical characteristics required to resist cavitation erosion. When molten metal or alloy flows and comes into contact with refractory material or coated furnace linings, cavitation erosion can occur. This phenomenon is particularly expected in metallurgy, especially in casting operations. Alumina-based refractories, specifically low cement castable (ALCC), are often used in furnace lining applications due to their superior properties, such as high refractoriness, thermal stability, and mechanical characteristics. Mullite is another refractory material frequently used in foundry lining applications. It can be utilized as a coating in casting processes, such as the Lost Foam process, which is a novel method for producing high-quality, cost-effective castings. These two refractory materials were chosen to study their behavior under cavitation conditions. An ultrasonic vibratory test with a stationary specimen (ASTM G-32) was used for experimental cavitation determination. The results of mass loss and surface morphological parameters of degradation revealed that ALCC samples eroded predominantly at the surface, while the mullite samples exhibited more significant degradation by depth.

Properties of Durable Mullite Bodies Manufactured from Waste Clay-Diatomite

Mon, 15 Jul 2024 00:00:00 +0000

Durable mullite bodies have been fabricated using diatom frustules from diatomite powder as the Si source and Al-nitrate as the Al precursor, resulting in fibrous pore morphology. The hard mullite ceramics prepared by mold pressing without additives showed high compressive strength (up to 133 MPa when sintered at 1500 °C). The diatomite-nitrate samples were sintered at three temperatures (1300, 1400, and 1500 °C) for 2 hours. XRPD analysis of the sintered samples showed that the crystalline mineral phases mainly comprise mullite, cristobalite, and corundum. SEM results indicate the presence of rod-like mullite grains measuring 5 µm in length and 500 nm in diameter (aspect ratio 1:10). XRPD analysis of the samples sintered at 1300 °C demonstrated good thermo-mechanical stability and the formation of new hard phases (mullite, corundum, and cristobalite), making the analyzed diatomaceous earth suitable to produce various types of ceramic, construction, and thermal insulating materials.

The Microstructure Characterization of Al-alloy AW 5454 Intended for Ecological Laser Hybrid Welding

Matjaž Balant, Rebeka Rudolf — Mon, 15 Jul 2024 00:00:00 +0000

The article deals with the presentation of the microstructure characterization of Al-alloy AW 5454, which is intended for laser hybrid welding. In the first part, the procedure of laser hybrid welding and comparison to other laser surface modification techniques is presented. In the following, the key methods of metallographic characterization and hardness measurements at selected locations of Al-alloy AW 5454 are presented, which made it possible to carry out a scientific evaluation of the obtained results. The goal of the research was to gain insight into the microstructure of Al-alloy AW 5454, which in the future will make it possible to determine those technological parameters of laser hybrid welding that have the greatest influence on the resulting final microstructure and thus on the properties of the weld.