Mechanical and Thermal Properties of Polylactide (PLA) Composites Modified with Mg, Fe, and Polyethylene (PE) Additives

In this article, polylactic acid-based composites reinforced with 5% of polyethylene, iron, and magnesium powders were prepared by extrusion and compressed under the pressure of about 10 MPa and characterized. These composites were mechanically, thermally, and morphologically evaluated. It was found, compared to the pure polylactic acid (PLA), an improvement in tensile strength (both σ and YS0.2) was obtained for the composite with the iron powder addition, while the magnesium powder slightly improved the ductility of the composite material (from 2.0 to 2.5%). Degradation studies of these composites in the 0.9% saline solution over a period of 180 days revealed changes in the pH of the solution from acidic to alkaline, in all samples. The most varied mass loss was observed in the case of the PLA-5%Mg sample, where initially the sample mass increased (first 30 days) then decreased, and after 120 days, the mass increased again. In the context of degradation phenomenon of the tested materials, it turns out that the most stable is the PLA composite with the Fe addition (PLA-5%Fe), with highest tensile strength and hardness

Role of Cr and Ti contents on the microstructure and mechanical properties of ODS ferritic steels

Six oxide dispersion strengthened (ODS) ferritic steels, with the composition of Fe-(12-14)Cr-2W-(0.1-0.3-0.5)Ti-0.3Y(2)O(3) (wt.%), have been prepared by mechanically alloying elemental powders of Fe, Cr, W, and Ti with Y2O3 nano-particles followed by hot isostatic pressing. The influence of the chemical composition on the microstructure and mechanical properties of various materials was studied. It was found that the chromium content has a significant influence on the microstructure and mechanical properties of the compacted ingots. The 14Cr ODS steel exhibits slightly higher ultimate tensile strength and yield strength values than the 12Cr ODS steel. The total elongation and uniform elongation of both materials, in general, decrease with raising the test temperature, although in the case of the 12Cr ODS steel the elongation is about 30% higher than that of the 14Cr ODS material. In what concerns the effect of titanium content it can be concluded that variations between 0.1 and 0.3% have no visible effects on the microstructure and Charpy impact properties of compacted specimens. However, the microstructure of specimens with 0.5%Ti contains large TiO2 particles with a size in the range of 50-500nm, which have detrimental influence on the mechanical properties of that material

A Vertical Fountain Dryer Adjusted for Sawdust and Wood Chips Drying

This article presents the preliminary results on the drying process in a fountain dryer designed and adapted to drying waist sawdust and/or chips of various morphology and moisture content. In terms of drying technology, it is important to reduce the demand for heat and electricity. The phenomena occurring during the drying of sawdust in a fountain dryer were analyzed. Modifications of a typical fountain dryer were proposed in order to dry the chips, to obtain appropriate moisture and quality suitable for the process of their further granulation for the production of pellets. The test stand and the most important properties of the fountain dryer were described and discussed. Such characteristic aims of the device, i.e., efficiency, combustion, air and exhaust gas flow measurements, among others, were presented. The characteristics of the sawdust drying curves as a function of temperature were also determined. Computer simulations of heat exchange, air, and exhaust gas flow velocities were also performed and compared with the results obtained directly from the modified test stand. The maximum combustion of sawdust measured during startup of the furnace was 0.14 m3/h, which is 0.46 m3 of the fuel consumption for the production of 1000 kg. Drying times of wet sawdust is relatively short and takes ~50 s for (weight of wet sawdust 4.75 kg, with moisture of 35%) the relatively low air temperature of 175 °C

Experimental and numerical small punch tests of the 14cr ods ferritic steel

Nowadays, various small specimen test techniques have gained wide popularity and appreciation among researchers as they offer undoubtful benefits in terms of structural material characterisation. This paper focuses on small punch tests (SPTs) performed on small-sized disc specimens to assess the mechanical properties of 14Cr oxide dispersion strengthened (ODS) steel. A numerical model was established to support experimental data and gain deeper insight into complex strain states developing in a deformed specimen. Modern evaluation procedures were discussed for obtaining mechanical properties from the small punch force-deflection response and were compared with the literature. Applicability and universality of those relations at different test conditions were also studied. It appeared that different ball diameters used had negligible influence on yield point but strongly affected ultimate strength estimation. It was found that friction belongs to decisive factors determining strain distribution in samples, as dry conditions increase the peak strain and move its location farther from the punch pole

Viability analysis of pine sawdust drying in a fountain dryer

This article presents an analysis of the physico-chemical properties of pine sawdust originating from the area of the Knyszyńska Forest, in the context of the possibility of the sawdust drying in a fountain dryer. Several tests were carried out on dry pine sawdust with 45% moisture, including chemical composition, calorific value, ash content as well as morphological changes of wet and dried material. The water storage mechanism in chips and the mechanism of formation of a fountain bed were also discussed. Based on the obtained results, several technical solutions and modifications of the fountain dryer were proposed. These modifications enable sawdust of heterogeneous size and shape to be dried in a fountain dryer as well as additional functional properties

Formation and Microstructural Evolution of Ferritic ODS Steel Powders during Mechanical Alloying

Ferritic ODS steel elemental powder compositions with various Zr content (0.3–1.0 wt.%), ground in a Pulverisette 6 planetary ball mill, were extensively studied by X-ray diffraction line profile analysis, microscopic observations, microhardness testing and particle size measurements. A characteristic three-stage process of flattening the soft powders, formation of convoluted lamellae and, finally, formation of nanocrystalline grains was observed. In order to quantify the microstructural properties, expressed mainly in terms of crystallite size and dislocation density, a methodology for detailed and accurate microstructure analysis of nanosized and severely deformed materials was proposed by the Whole Powder Pattern Modelling (WPPM) approach. In the case of the proposed ODS alloy composition, the overlapping of Fe and Cr Bragg reflections makes the microstructure analysis certainly more complicated. The results showed that the microstructure of powders evolved towards the nanocrystalline state consisting of fine (diameter of ~15 nm) and narrowly dispersed domains, with extensive dislocation density exceeding 1016 m−2

Microstructure, Mechanical, and Corrosion Properties of Ni-Free Austenitic Stainless Steel Prepared by Mechanical Alloying and HIPping

An influence of the powder metallurgy route on the phase structure, mechanical properties, and corrosion resistance of Fe–18%Cr–12%Mn–N nickel-free austenitic stainless steel as a potential material for medical applications were studied. The powder was mechanically alloyed in a high purity nitrogen atmosphere for 90 h followed by Hot Isostatic Pressing at 1150 °C (1423 K) and heat treatment at 1175 °C (1423 K) for 1 h in a vacuum with furnace cooling and water quenching. More than 96% of theoretical density was obtained for the samples after Hot Isostatic Pressing that had a direct influence on the tensile strength of the tested samples (Ultimate Tensile Strength is 935 MPa) with the total elongation of 0.5%. Heat treatment did not affect the tensile strength of the tested material, however, an elongation was improved by up to 3.5%. Corrosion properties of the tested austenitic stainless steel in various stages of the manufacturing process were evaluated applying the anodic polarization measurements and compared with the austenitic 316LV stainless steel. In general, the heat treatment applied after Hot Isostatic Pressing improved the corrosion resistance. The Hot Isostatic Pressing sample shows dissolution, while heat treatment causes a passivity range, the noblest corrosion potential, and lower current density of this sample

Reduced activation ODS ferritic steel - recent development in high speed hot extrusion processing

The paper presents the microstructure and mechanical properties of an oxide dispersion strengthened (ODS), reduced activation, ferritic steel, namely the Fe-14Cr-2W-0.3Ti-0.3Y(2)O(3) alloy, which was fabricated by hot isostatic pressing followed by high speed hydrostatic extrusion (HSHE) and heat treatment HT at 1050 degrees C. Transmission electron microscopy (TEM) observations revealed significant differences in the grain size and dislocation density between the as-HIPped and as-HSHE materials. It was also found that the microstructure of the steel is stable after HT. The HSHE process improves significantly the tensile and Charpy impact properties of the as- HIPped steel. The ultimate tensile strength at room temperature increases from 950 up to 1350 MPa, while the upper shelf energy increases from 3.0 up to 6.0J. However, the ductile-to-brittle transition temperature (DBTT) remains relatively high (about 75 degrees C). These results indicate that HSHE is a promising method for achieving grain refinement and thus improving the mechanical properties of ODS ferritic steels. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei