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In pressure die casting, due to the high speed of the liquid metal injection into the mold, a microstructure with refined grains is obtained and defects such as microporosity and microshrinkage, cold shut, and misrun can occur. These defects can occur due to deficiencies in the tooling design (injection mold), in the definition of calculation parameters, or even in the control of the injection parameters. The aim of this paper is to analyze the influence of injection phase velocities (first and second phases) on the microstructure and mechanical properties of the Aluminum A380 alloy. Standard test samples were cast under die pressure in a cold chamber injection machine. The range injection speeds of the process were 0.10 m/s, 0.25 m/s and 0.50 m/s for the of the first phase, and 0.6 m/s, 1.5 m/s 3.0 m/s of the second phase. The mechanical properties characterization was performed by tensile and hardness tests and the microstructural characterization by optical microscopy. The results indicated that the injection speed does not influence the strength limit of both the first and the second injection phases. However, the level of porosity and misruns changed as a function of the speed variations, factors that affect the result of the elongation and yield point of the die-casting products. [ABSTRACT FROM AUTHOR]

The energy that a material absorbs during its fracture is a very important parameter in the steels. In most parts of the applications in the Market, it is searched a kind of steel that can be resistant and in the same time can have tenacity so in that way, they can be able to avoid catastrophic and fragile failures. On this way, the heat treatment of hardening and tempering is one of the alternatives to be applied for changing the mechanical properties of a big variety of steels. Like this, it is very important that the influences of different conditions of heat treatment that are applied in the same alloy be studied, evaluating the mechanical and microstructural properties which were obtained after the heat treatment. This article has the aim to evaluate the behavior of tenacity of SAE 8640 steel, for that, fifteen pieces of tests were made, they were submitted to the same hardening process and separated in three categories of tempering process (200°C, 400°C e 600°C). It was performed metallographic analysis to get the images of the microstructure as stereomicroscope and electron microscope scanning to get the images of fractured surface together with a hardness test and rehearsal Charpy respecting the ASTM E-23 standard, after the analysis, it was possible to conclude that the material which was submitted to 600°C heat treatment had its hardness decreased and its tenacity increased together with a more ductile behavior than when it was submitted to the materials to200°C e 400°C which kept similar characteristics. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the impact caused in a high strength steel called LN 700 using two different drilling process, being conventional drilling and flow drilling submitted to the threading process (flow tapping process). Thereunto, some parameters were monitored, such as, microstructure, microhardness, tensile strength and fatigue life. The data obtained during this study show the positive influence of the burr from the flow drilling process. When analyzed the fatigue life of the material, it's verified that flow drilling bear a greater number of cycles than the conventional drilling process. Therefore, is noted some benefits form burr in the flow drilling process. [ABSTRACT FROM AUTHOR]

The objective of this work was to produce, by high-energy milling, Zamak 2 alloy powder and consolidated it by hot pressing. The characterization of the powders was performed in terms of morphology and microstructure, while the consolidated products were characterized in terms of microstructure, final densification and hardness. Zamak 2 alloy powder was prepared by milling the elementary powders (Zn, Al, Cu) in an attrition mil at 400 rpm, in argon atmosphere and varying times. The obtained powder was compacted (400 MPa) and then hot pressed (350°C/500 MPa). The micrographs showed that 10 h of milling were sufficient to reach the state of equilibrium between welding and fracture. Zamak 2 powder showed low compressibility due to the increased deformation resistance during the high-energy milling. After consolidation, the alloy presented a 10% increase in density, good cohesion between the particles and homogeneous distribution of α and ε phases. The hardness of the consolidated sample was statistically equal to that of the Zamak ZL4CZAP casting alloy. [ABSTRACT FROM AUTHOR]

Concrete is a material that can be defined, in its hardened state, as an artificial rock, by virtue of its properties of strength, hardness and others. However, it does have some deficient features, they are, which can be done with the reduced ability to make the changes before the break. With the purpose of this correction were progressed with additions, based on work reinforced with fiber. Fiber Reinforced Concrete (CRF) is a composite, that is, a material that has some type of reinforcement. Fiber reinforced concrete and reinforced concrete are examples of composites, in which they are organized by two different phases, being called the fragile matrix and reinforcement. The CRF can be used in large, deep works. [ABSTRACT FROM AUTHOR]

The hardness test is one of the most important mechanical tests used by the metal-mechanical industry. The quality assurance of the measured results is mainly due to the human factor, which is involved in the verification, adjustment, and operation of the measuring equipment. Therefore, the main goal of this paper is to design and develop verification standards for Brinell (HB) and Rockwell (HRC) scales from low alloy carbon steels subjected to different types of heat treatment. In order to assure the reliability of the hardness values of the verification standards, they have been measured on equipment calibrated by laboratories belonging to the Brazilian Calibration Network (RBC). The results showed similar values based on ten measurements made on the standards surface. [ABSTRACT FROM AUTHOR]

SiC is a ceramic used as a structural material due to some characteristics such as: high resistance to wear, thermal shock and oxidation. Sintering of these materials without the use of pressure is impossible, unless sintering additives are used. This fact is due to the high ratio between the grain boundary energy and the SiC surface energy, which prevents high sintering densities. This research promoted the production of alumina and yttria nanometric powders by SHS ("High Temperature Self-Sustaining Combustion Synthesis") and its use as a SiC sintering additive. The objective of this work was to compare the properties of hexagonal carbide silicon additive with aluminum oxides and commercial yttrium with silicon carbide plates added with aluminum oxides and nanometric yttrium produced by SHS and heat treated at 1200°C. It was observed that the plates added with powders produced by the heat treated SHS reaction presented similar or better results when compared to the commercial additive. [ABSTRACT FROM AUTHOR]

The main goal of this work was quality control of post-harvest and performance in production of rounded tomatoes. The absence of post-harvest treatment justifies the existence of quality control tools across the line. There were established quality control parameters: size, weight, ºBrix, firmness, color and its relationship with lycopene content, in order to characterize four varieties of round tomatoes (A, B, C, D) fresh and refrigerated, produced in the western region of Portugal. The fruits were harvested in three different zones of the plants at first crop and in the first cluster, the second fruits were harvested from the third and fourth cluster, the last harvest fruits were in the sixth and last cluster for quality control. There were analysed five fresh fruits and another five fruits were assessed after cooled for one week in a refrigerator at 5 °C and another five the other in cold storage at 4 °C. It was found that all cultivars can reach high quality of productions, highlighting the variety D by the highest values of °Brix and estimated lycopene content. It can be considered that this cultivar has major advantages for production and for marketing. [ABSTRACT FROM AUTHOR]

In this paper, the heat treatment by electromagnetic induction was applied in motorcycle crankshaft. An electromagnetic induction device of Straight Inductor type has been used, whose heat to warm hardened region is generated on the part itself. Measuring the depth of hardened layer, metallographic tests, optical microscopy and X-rays diffraction (XRD) characterization and hardness tests (Rockell C- HRC), ranging from the core to the surface of the hardened region, were performed. The results show that the depth of hardening has reached the value 1.5 mm, and the hardness observed for the three tested crankshafts were 20, 22 e 23 HRC at the core, and 54, 54 e 58 HRC at the treated surface, respectively. The microstructure at the core of the heat treated specimen is composed of pro-eutectoid ferrite network around the grains of toostita perlite. The thermally treated region is composed by an area of fine carbides dispersed in refined ferrite-rich matrix, resulting in a tempered-martensite microstructure. The comparison of the experimental results of this work to quality standards, established by the motorcycle manufacturer, proved the effectiveness of surface heat treatment applied to the crankshaft. [ABSTRACT FROM AUTHOR]

The aluminum alloy A356 (Al-Si-Mg) are used extensively in manufacturing components for automotive and aerospace industries due to their physical and mechanical properties. They are used in many structural applications requiring high strength at low weight, high strength and impact resistance, low coefficient of thermal expansion, good corrosion resistance and excellent fluidity, such as casting alloys for the production of light alloy wheels. In this sense, the main objective of this work is to evaluate the effects of T6-precipitation heat treatment on the microstructure and mechanical properties of the A356 Al- 7SI-0.3Mg alloy. To this end, a wheel of motorcycle has been used and the heat treatment administered in the manufacturing industry, as established standards. The results show a eutectic microstructure composed of Si (spherical silicon) and Fe intermetallic which has been observed between the dendritic ramifications. Rocwell B - hardness tests were carried out and the values correspond to the established standards. [ABSTRACT FROM AUTHOR]

This paper employs the method for evaluating abrasion proposed by Golovanevskiy e Bearman (2008). This method, Gouging Abrasion Test, employs high-stress load gouging/sliding impact wear. The method consists of a steel wear tool with a 90" sharp conical tip. This tip attacks a rock sample in a swinging trajectory with an impact energy of 300 J and a speed of around 5.2 m/s. The Gouging Abrasion Index (Gi) is determined as 10 times the average diameter in millimeters of the conical tip (now flat) after one event of wear. This paper evaluates the Gouging Abrasion Test suitability in a small group of rocks that represents some of the main types to be found in Brazil's rock cutting, drilling and crushing works. Its relationship to other usual tests like uniaxial compressive strength, Amsler abrasive wear and Knoop hardness were also verified. The results show high correlation between Gi and Knoop hardness (R² = 0,94), low correlation with Amlser wear (R² = 0,41) and no relation to uniaxial compressive strength. [ABSTRACT FROM AUTHOR]

Nitriding has been used for martensitic stainless steels to increase surface hardness. However, problems may arise related to surface hardness, core hardness, and corrosion wear resistance. This work presents results on the relation between heat treatment and plasma nitriding parameters in order to obtain the best properties combination. Heat treatments were carried out to reach hardness between 38 and 50 HRC. Plasma nitriding were carried out on temperatures ranging from 480 to 560°C, using times from 1 to 16 hours. X-ray diffraction, optical microscopy, Rockwell C hardness and Vickers microhardness techniques were used to characterize the treatments. Results show that plasma nitriding increases surface hardness up to 1,500 HV. When substrate is quenched and tempered to 50 HRC the plasma nitriding temperature has a strong influence on hardening behaviour. Increasing nitriding temperature from 480 to 560°C substrate hardness drops from 50 to 38 HRC. Otherwise, using start tempered and quenched core hardness close to 38 HRC full surface hardening is reached after plasma nitriding and no core hardness drop is verified. As a consequence different routes for heat treatment and plasma nitriding are discussed herein. [ABSTRACT FROM AUTHOR]

Hard metals are a group of materials known as sintered composites involving hard phases (carbides) with a metallic phase, being widely used in applications where you want high hardness and wear resistance combined with high toughness. This article presents the results of adding 1% by weight of the elements Nb, Ti, Cr and Mo on the microstructure of the hard metal from a commercial composite of WC-6Co. In this composite was added 1.5% (by weight) of zinc stearate as lubricant and sintered at a temperature of 1450°C in an atmosphere of argon. Aiming to analyze the product efficiency was held on micro structural characterization through the testing of green density, shrinkage, sintered density, microstructure and microhardness. [ABSTRACT FROM AUTHOR]

The present study was undertaken to investigate the influence of the raw materials hardness and process temperature on deformation behavior of rolled cooper flat wires. Several samples were laminated using different combinations of the parameters above mentioned in order to evaluate the deformation behavior. Deformation was evaluated by calculation of axial and radial deformation relationship (Anisotropy parameter), additionally mechanical and metallographic characterization of the experimental samples and raw materials were realized. The results indicated significant influence of the raw material hardness and rolling temperature on the copper deformation behavior, showing increases in Anisotropy parameter with decrease in hardness and increase in rolling temperature. [ABSTRACT FROM AUTHOR]

Austenitic stainless steels cannot be conventionally nitrided at temperatures near 550°C due to the intense precipitation of chromium nitrides in the diffusion zone. The precipitation of chro-mium nitrides increases the hardness but severely impairs corrosion resistance. Plasma nitriding allows introducing nitrogen in the steel at temperatures below 450°C, forming pre-dominantly expanded austenite (&#x03B3N), with a crystalline structure best represented by a special triclin-ic lattice, with a very high nitrogen atomic concentration promoting high compressive residual stresses at the surface, increasing substrate hardness from 4 GPa up to 14 GPa on the nitrided case. [ABSTRACT FROM AUTHOR]

Precipitate-hardened stainless steel was developed in 1945 as a consequence of the aerospace industry's need for a high-strength steel that would be resistant to corrosion at high temperatures, and easily welded exceeding the properties of conventional stainless steel. This steel possesses substitutional martensitic microstructures that can afterwards be hardened by precipitation. For this research, two types of steel with alternative compositions were produced by using Nb as a precipitate producer, and PH13-8Mo steel for comparison purposes in terms of mechanical and corrosive resistance. Steel 1 showed corrosive resistance similar to PH13-8Mo and Steel 2 presented mechanical resistance close to that of PH13-8Mo. [ABSTRACT FROM AUTHOR]

Among the techniques used to improve materials performance, deposition on the surface of components is a proper way of recovering worn elements. Thermal spraying processes were developed during the last few years and they are a very suitable method to obtain layers with high hardness for protecting or repairing the base component. Employing these processes, it is possible to overlay metallic substrates with polymers, metals and ceramics. Among these processes are: HVOF, Arc-Spray and Flame-Spray. The selection of a particular type of stainless steel for an application involves some considerations, as the corrosion resistance of the alloy, mechanical properties, manufacture feasibility and cost. In this work, used were samples of AISI 1045 steel, coated with stainless steel AISI 420, using the techniques of Arc-Spray, HVOF and Flame-Spray for the comparative study of their corrosion resistance in sea water, aimed at producing low-cost alternative pieces, compared with massive pieces of steel. The best performances in terms of hardness, porosity levels and corrosion resistance of the layers occurred in the following sequence growing: Flame-Spray, Arc-Spray, and HVOF. [ABSTRACT FROM AUTHOR]