Studying the Damage Evolution and the Micro-Mechanical Response of X8CrMnNi16-6-6 TRIP Steel Matrix and 10% Zirconia Particle Composite Using a Calibrated Physics and Crystal-Plasticity-Based Numerical Simulation Model

The mechanical behavior of newly developed composite materials is dependent on several underlying microstructural phenomena. In this research, a periodic 2D geometry of cast X8CrMnNi16-6-6 steel and 10% zirconia composite is virtually constructed by adopting microstructural attributes from literature. A physics-based crystal plasticity model with ductile damage criterion is used for defining the austenitic steel matrix. The zirconia particles are assigned elastic material model with brittle damage criterion. Monotonic quasi-static tensile load is applied up to 17% of total strain. The simulation results are analyzed to extract the global and local deformation, transformation, and damage behavior of the material. The comprehensively constructed simulation model yields the interdependence of the underlaying microstructural deformation phenomena. The local results are further analyzed based on the interlocked and free regions to establish the influence of zirconia particles on micro-mechanical deformation and damage in the metastable austenite matrix. The trends and patterns of local strain and damage predicted by the simulation model results match the previously carried out in-situ tensile tests on similar materials.

Experimental Investigation of the Friction Stir Weldability of AA8006 with Zirconia Particle Reinforcement and Optimized Process Parameters

A lightweight, highly corrosive resistant, and high-strength wrought alloy in the alumi-num family is the Aluminium 8006 alloy. The AA8006 alloy can be formed, welded, and adhesively bonded. However, the recommended welding methods such as laser, TIG (Tungsten Inert Gas welding), and ultrasonic are more costly. This investigation aims to reduce the cost of welding with-out compromising joint quality by means of friction stir welding. The aluminum alloy-friendly re-inforcement agent zirconia is utilized as particles during the weld to improve the performance of the newly identified material AA8006 alloy in friction stir welding (FSW). The objectives of this research are to identify the level of process parameters for the friction stir welding of AA8006 to reduce the variability by the trial-and-error experimental method, thereby reducing the number of samples needing to be characterized to optimize the process parameters. To enhance the quality of the weld, the friction stir processing concept will be adapted with zirconia reinforcement during welding. The friction stir-processed samples were investigated regarding their mechanical proper-ties such as tensile strength and Vickers microhardness. The welded samples were included in the corrosion testing to ensure that no foreign corrosive elements were included during the welding. The quality of the weld was investigated in terms of its surface morphology, including aspects such as the dispersion of reinforced particles on the welded area, the incorporation of foreign elements during the weld, micro defects or damage, and other notable changes through scanning electron microscopy analysis. The process of 3D profilometry was employed to perform optical microscopy investigation on the specimens inspected to ensure their surface quality and finish. Based on the outcomes, the optimal process parameters are suggested. Future directions for further investigation are highlighted.

Moment Dynamics of Zirconia Particle Formation for Optimizing Particle Size Distribution

We study the particle formation process of Zirconia ( ZrO 2 )-based material. With a model-based description of the particle formation process we aim for identifying the main growth mechanisms for different process parameters. After the introduction of a population balance based mathematical model, we derive the moment dynamics of the particle size distribution and compare the model to experimental data. From the fitted model we conclude that growth by molecular addition of Zr-tetramers or Zr-oligomers to growing particles as well as size-independent particle agglomeration takes place. For the purpose of depositing zirconia-based material (ZrbM) on a substrate, we determine the optimal process parameters such that the mineralization solution contains preferably a large number of nanoscaled particles leading to a fast and effective deposition on the substrate. Besides the deposition of homogeneous films, this also enables mineralization of nanostructured templates in a bioinspired mineralization process. The developed model is also transferable to other mineralization systems where particle growth occurs through addition of small molecular species or particle agglomeration. This offers the possibility for a fast determination of process parameters leading to an efficient film formation without carrying out extensive experimental investigations.

Influence of elongated zirconia particles on microstructure and mechanical properties of yttria stabilized zirconia polycrystals

Yttria stabilized tetragonal zirconia polycrystals were prepared using mixtures of two different powders. One is composed of nanometric particles of 3.5mol% Y2O3 solid solution in ZrO2 and the other one of pure zirconia particles. The latter shows elongated particles of about 200 nm length and monoclinic symmetry and the former consists of isometric tetragonal particles of about 7 nm size. Both powders were synthesized under hydrothermal conditions at 240?C in water (the 3.5mol% Y2O3-ZrO2 solid solution) or in 4M NaOH solution (the pure ZrO2 powder). Two homogenous mixtures of these powders were prepared; the one with 5wt.% and the other one with 10 wt.% of the elongated zirconia particles. Compacts of 10mm diameter were isostatically pressed (250MPa) and sintered in a dilatometer furnace at 1400?C with no soaking time. A set of samples heated up to the selected temperatures allowed us to follow phase changes of the materials vs. temperature by X-ray diffraction. It was confirmed that all materials show tetragonal symmetry at the final temperature (1400?C). Density and mean grain size decrease with the elongated zirconia particle additives. The dense samples were polished and their hardness and fracture toughness were determined by Vickers indentation. No hardness changes, due to the elongated zirconia particles additives, were observed, but essential increase of fracture toughness occurred. The observations of the crack runs suggest crack deflection as a potential mechanism of the fracture toughness increase.

Effect of the Sandblasting Process on the Surface Properties of Dental Zirconia

This paper presents the effect of the sandblasting and sintering processes on the surface properties of some commercial yttria stabilized zirconia (Y-TZP) for monolithic dental restorations in dentistry. The surface properties of dental zirconia can be improved further through various surface treatment methods, like surface abrasion, roughening, chemical treatment, tribochemical coating, or selective infiltration etching. But all these treatments are made on the sintered samples, not on the pre-sintered discs as are delivered by the dental suppliers. The hypothesis of this paper was that the mechanical effect on the surface of pre-sintered disc of Y-TZP assured by airborne-particle abrasion with alumina will be maintained after the sintering process. Additionally, we will follow the presence of alumina particles on the Y-TZP surface after airborne-particle abrasion process. Surface modifications of the experimental samples was performed by sandblasting for 15 s with Al2O3 particles (average particle size 83 mm) at pressure of 2 bars, using a SAB-Caloris equipment. Morphological and surface changes in the sandblasted, respectively sandblasted and sintered samples of Y-TZP are examined by using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. It is found that the surface modifications made on the pre-sintered Y-TZP disc remain after sintering process, which not affects these mechanical modifications of the surface. Also, it was detected the presence of alumina particles on the Y-TZP samples after airborne-particle abrasion process and for this reason we recommend the use of zirconia particle for airborne-abrasion process.