Effect of Two Brands of Glaze Material on the Flexural Strength and Probability of Failure of High Translucent Monolithic Zirconia

(1) Background: The effect of glazing on the mechanical properties of monolithic high translucent zirconia is not well reported. Therefore, the purpose of this study was to evaluate the effect of glazing on the flexural strength of high translucent zirconia; (2) Methods: Ninety specimens were prepared from second-generation 3Y-TZP high translucent blocks and divided into three groups. Glaze materials were applied on one surface of the specimen and subjected to a four-point bending test and flexural stress and flexural displacement values were derived. Descriptive fractographic analysis of surfaces was conducted to observe the point of failure and fracture pattern.; (3) Results: Control-nonglazed (647.17, 1σ = 74.71 MPa) presented higher flexural strength values compared to glaze I (541.20, 1σ = 82.91 MPa) and glaze II (581.10, 1σ = 59.41 MPa). Characteristic strength (σƟ) from Weibull analysis also observed higher (660.67 MPa) values for the control specimens. Confocal microscopy revealed that glazed surfaces were much rougher than control surfaces. Descriptive fractographic analysis revealed that there was no correlation between the point of failure initiation and flexural strength; (4) Conclusions: The test results demonstrated that glazing significantly decreased the flexural strength and flexural displacement of the zirconia specimens.

The Investigation of Microstructure and Mechanical Behavior and the Fractographic Analysis of the Ti49.1Ni50.9 Alloy in States with Different Activation Deformation Volumes

In this article, the microstructure and mechanical behavior of the Ti49.1Ni50.9 alloy with a high content of nickel in a coarse-grained state, obtained by quenching, ultrafine-grained (obtained through the equal-channel angular pressing (ECAP) method) and nanocrystalline (high pressure torsion (HPT) + annealing), were investigated using mechanical tensile tests at different temperatures. Mechanical tests at different strain rates for determining the parameter of strain rate sensitivity m were carried out. Analysis of m showed that with an increase in the test temperature, an increase in this parameter was observed for all studied states. In addition, this parameter was higher in the ultrafine-grained state than in the coarse-grained state. The activation deformation volume in the ultrafine-grained state was 2–3 times greater than in the coarse-grained state at similar tensile temperatures. Fractographic analysis of samples after mechanical tests was carried out. An increase in the test temperature led to a change in the nature of fracture from quasi-brittle–brittle (with small pits) at room temperature to ductile (with clear dimples) at elevated temperatures. Microstructural studies were carried out after the tensile tests at different temperatures, showing that at elevated test temperatures, the matrix was depleted in nickel with the formation of martensite twins.

Fatigue behaviour of Vossloh SKL14 tension clamps

<p>The reliability of the railway superstructure depends, among other things, on the actual fastening of the rail to the sleepers. This structure is extremely dynamically loaded. In the paper, the attention is paid to the flexible Vossloh W14 fastening system with the use of SKL14 tension clamps. These clamps are often damaged by fatigue failures, especially in curves of small radii (R &lt; 400 m). Within the research, fracture areas were identified and a fractographic analysis was performed. The analysis proved fatigue failure and, therefore, an estimation of the service life of the clamps was made. The evaluation was focused on a selected area of railway track where the fatigue-damaged clamps were found. The strain gauges were placed directly on the clamps at critical points and the obtained values were confronted with the experimentally obtained fatigue curve. Based on the presented findings, the service life of the clamps in the selected track was identified.</p>

Effects processing parameters and building orientation on the microstructural and mechanical properties of AlSilOMg parts printed by selective laser melting

SYNOPSIS The mechanical properties and microstructure of AlSilOMg alloy samples that were printed by selective laser melting (SLM) were studied to determine the effect of processing parameters and building orientation. After printing, the alloy was stress relieved at 250°C for 2 hours. The microstructures were analysed by optical microscopy and scanning electron microscopy (SEM) to determine the alloy phases and distribution. Phase transformation characteristics of the material were evaluated using differential scanning calorimetry (DSC). Mechanical properties were determined by subjecting the XY- and Z-built samples to tensile and nano-indentation testing. The samples from the tensile tests were then used to perform fractographic analysis by SEM. The microstructural properties in each orientation revealed a non-homogeneous microstructure which was characterized by a semi-elliptical tract and fine silicon precipitates, which were found to be softer along the fusion zone. The DSC thermograms revealed that the material underwent two phase transformations during the first heating cycle. The mechanical properties revealed a higher UTS, higher yield strength, and a lower percentage elongation in the Z orientation than in the XY orientation. Fractographic analysis showed that crack initiation in both orientations started from the surface in a brittle manner due to surface flows, and then propagated via microvoid coalescence. Keywords: AlSi10Mg alloy, additive manufacturing, mechanical propeerties, microstructure.

Microstructural and fractographic analysis of A359/Si3N4 surface composite produced by friction stir processing

High strength and lightweight materials are currently used in the automobile and defence sectors. In this framework, aluminium-based composites are a suitable choice due to their improved properties. The present study deals with the development of surface composites of A359/Si3N4 via friction stir processing. The varying percentage of reinforcement (2% to 6%) is the main criterion behind the study to observe its influence on mechanical, wear, thermal and corrosion properties. Investigations of microstructure and morphological characterization of the developed samples were conducted by optical light microscopy and scanning electron microscopy. Identification of the alloying elements, reinforcement materials and phase distribution is observed by EDS mapping. In addition, Raman spectroscopy and X-ray diffraction analysis were also conducted to validate the structural composition. As a research outcome, the effect of varying reinforcement percentage was examined on the tensile strength supported by fractographic analysis and hardness values. Apart from this, wear, thermal expansion and corrosion tests were conducted to assess the behavior of samples in different operation conditions. The results reveal the maximum tensile strength (478 MPa) and maximum hardness (119 HRB) with minimum wear loss (3.3 mg m–1), maximum thermal expansion (8.2 mm3) and maximum weight loss due to corrosion (0.0058 g) for A359/6%Si3N4 composite.