Effect of Cold Rolling on Cluster(1) Dissolvability during Artificial Aging and Formability during Natural Aging in Al-0.6Mg-1.0Si-0.5Cu Alloy

Natural aging after solution treatment has a negative effect on the precipitation strengthening of Al–Mg–Si alloys since Cluster(1) formed at a room temperature cannot be dissolved or transformed into precipitates during artificial aging at 170 °C. In this study, cold rolling is focused on as an alternative solution to pre-aging, which is a conventional method to prevent Cluster(1) formation. It is known that excess vacancies are necessary for cluster formation. Cold rolling suppresses cluster formation because excess vacancies disappear at dislocations introduced by cold rolling. In addition, it is expected that cold rolling accelerates the precipitation behavior because the diffusion of solute atoms is promoted by introduced lattice defects. The transition of Cluster(1) was evaluated by Micro Vickers hardness tests, tensile tests, electrical conductivity measurements and differential scanning calorimetry analyses. Results showed the negative effect of natural aging was almost suppressed in 10% cold-rolled samples and completely suppressed in 30% cold-rolled samples since Cluster(1) dissolved during artificial aging at 170 °C due to lowering of the temperature of Cluster(1) dissolution by cold rolling. It was found that the precipitation in cold-rolled samples was accelerated since the hardness peak of 10% cold-rolled samples appeared earlier than T6 and pre-aged samples.

Study for Performance Increase of a Extractor Device by Steel Replacement of AISI 304 Steel for AISI 420 Steel

The performance of an extractor device used in the food industry was studied from the development of structural analysis through computational modeling based on finite elements. These analyses considered the mechanical properties of AISI 304 and 420 stainless steels, in addition to the tribological aspects of the device in operation. Initially, uniaxial tensile tests were carried out according to the ABNT NBR 6892 standard and hardness tests were carried out according to ASTM E384, E92, and E18 standards. From the mechanical tests, structural analyses were carried out numerically on each of the components of the extractor device. After analyzing all the components, the device was assembled to be tested in operation. The wear and service life of devices made from these two materials were evaluated. From this study, it could be concluded that the extractor device made with AISI 420 stainless steel, in addition to having a lower manufacturing cost, suffered less wear and had an increase in service life of up to 650% compared to the extractor device made with steel stainless steel AISI 304.

SANS study on the stability of oxide nanoparticles in long-term thermally aged 9Cr-ODS steel

A 9Cr-oxide dispersion strengthened (ODS) steel was thermally aged at 873 K for up to 5000 hours. The size distribution and chemical composition of the dispersed oxide nanoparticles were analyzed by small angle neutron scattering (SANS) method under magnetic field. Combined with transmission electron microscopy (TEM), Vickers micro-hardness tests and electron backscattered diffraction (EBSD) measurements, all the results showed that the thermal treatment had little or no effect on the size distributions and volume fractions of the oxide nanoparticles in the ferromagnetic matrix, which suggested excellent thermal stability of the 9Cr-ODS steel.

Tensile and Hardness Properties of Cast 6063 Aluminium Rods produced from Sand and Squeeze Casting Moulds

This work presents experimental analysis to determine the effect of sand and squeeze casting methods on the Tensile and Hardness properties of AA6063 Aluminium. Sand and squeeze cast moulds were fabricated and used to produce Aluminium rods. The test samples from cast rods were subjected to Tensile and Hardness tests. The results obtained showed better Tensile and Hardness properties, in the squeeze cast samples that were produced under varied pressure. The hardness of squeeze casting varied from 72.9 to 82.3Hv, while that of sand casting had 70.0Hv. Also, Ultimate Tensile Strength increased with increased pressure in squeeze castings from 178.01 to 194.04MPa and 161.97 in sand castings. Conversely, the mechanical properties of the cast products improved from those of sand casting to squeeze casting. Therefore, squeeze cast products could be used in as-cast condition in engineering applications requiring high quality parts while sand casting may be used in as-cast condition for non- engineering applications or engineering applications requiring less quality parts

Microstructural evolution and mechanical properties of LM6 Al alloy

In this paper, multi-axial compression of LM6 Al alloy were performed at room temperature using strain of 0.2 in each pass. Total cumulative strains 0.6, 1.2 and 1.8, were applied in three, six and nine passes, respectively. Microstructural evolution is studied using light optical microscopy of the compressed specimen. Properties (tensile strength, hardness, toughness) of deformed specimens were studied using tensile and hardness tests, and relate them with their microstructures and fractographs. As passes increased from zero to nine, 62% of tensile strength of the material is increased along with hardness from 52 VHN to 74VHN.

Poly(L-lactic acid) Reinforced with Hydroxyapatite and Tungsten Disulfide Nanotubes

Poly(L-lactic acid) (PLLA) is a biocompatible, biodegradable, and semi-crystalline polymer with numerous applications including food packaging, medical implants, stents, tissue engineering scaffolds, etc. Hydroxyapatite (HA) is the major component of natural bone. Conceptually, combining PLLA and HA could produce a bioceramic suitable for implants and bone repair. However, this nanocomposite suffers from poor mechanical behavior under tensile strain. In this study, films of PLLA and HA were prepared with small amounts of nontoxic WS2 nanotubes (INT-WS2). The structural aspects of the films were investigated via electron microscopy, X-ray diffraction, Raman microscopy, and infrared absorption spectroscopy. The mechanical properties were evaluated via tensile measurements, micro-hardness tests, and nanoindentation. The thermal properties were investigated via differential scanning calorimetry. The composite films exhibited improved mechanical and thermal properties compared to the films prepared from the PLLA and HA alone, which is advantageous for medical applications.

Neural Network Model for Synthesis of Thermally Sprayed (AI/AI2O3) Composite Protective Coatings

Al2O3 and Al2O3–Al composite coatings were deposited on steel specimens using Oxy-acetylene gas thermal spray gun. Alumina was mixed with Aluminum in six groups of concentrations (0, 5, 10,12,15 and 20% ) Al2O3, Specimens were tested for corrosion using Potentiodynamic polarization technique. Further tests were conducted for the effect of temperature on polarization curve and the hardness tests for the coated specimens. At first, Modelling was carried out using MINITAB-19, least square method, as a 2nd degree nonlinear model, bad results were achieved because of the high nonlinearity. Better result was achieved using neural network fitting tool. The network was designed using five neurons in the hidden layer and the input was I input with two layers, the electrical potential and alumina concentration.

Kekerasan Produk Metalurgi Serbuk Berbahan Limbah Aluminium dengan Metode Kompaksi Bertahap

The product resulting from the powder metallurgy process has advantages in terms of mechanical properties and physical properties. Material engineering by mixing several types of metal powders is very possible to do. The composition of this powder metallurgical process material is a mixture of aluminum powder (80%), copper powder (15%) and silicon carbide powder (5%) by weight then compacted with a compaction load gradually, starting with a load of 3 tons, holding for 3 minutes, followed by a load of 3 tons. 4 tons were held for 3 minutes and the last 5 tons were held for 3 minutes by pre sintering 1250C. Sintering in the kitchen with temperature variations of 4500C, 5000C and 5500C and sintering time for 60 minutes. Tests carried out on the specimens were hardness tests using the Rockwell (HRF) method. The results showed that the hardness of a single material has a hardness of around 35 HRF. The average hardness of the mixed material at a sintering temperature of 4500C is 80 HRF. The hardness of the mixed material at a sintering temperature of 5000C on average is 74 HRF. Meanwhile, the hardness of the mixed material at a sintering temperature of 5500C averaged 52 HRF. It can be concluded that the application of heat at the time of compaction and the selection of the sintering temperature greatly affect the hardness of the product resulting from the powder metallurgy process.