FOUNDING RESEARCH JOURNAL
Year:2021 | Volume:5 | Issue:2|Papers Count:6

In this study, the effects of Sb addition and casting modulus on the microstructure, morphology of graphite, and mechanical properties of ductile cast iron were investigated. For this purpose, a ductile cast iron with different casting modulus of 8, 15 and 30 mm were cast. Also, in order to examine the effect of Sb element in another mold with similar conditions, 0.01 wt% of Sb was added to the melt followed by the microstructure evaluation using an optical microscope. MIP4 image processing software was used to analyze the microstructure images. Brinell hardness and tensile tests were conducted to evaluate the mechanical properties. The results of this study showed that with increasing the casting modulus, nodule count decreased from 500 to 235 nodule per square mm, also nodularity decreased from 71 to 63%. In addition, the study of the results of hardness and the tensile test showed that with increasing the casting modulus, the hardness decreases from 289 to 212 HB and the yield strength from 430 to 350 MPa. Comparison of samples containing Sb and without Sb showed that Sb increased the nodularity, nodule count and volume fraction of perlite. For example, for the sample with 1 mm modulus, the presence of Sb increased the nodule count by 49%, improved the nodularity from 65% to 68.5%, and also increased the perlite volume fraction by almost 11%.

Abstract: The aim of this study was to investigate the creep behaviour of GTD111 nickel base superalloy produced by directional solidification method. First, a cluster of cylinders of this alloy were cast by Bridgman method. Then, by preparing the tensile specimens, they were subjected to creep test at 870˚C and different stresses. Creep behaviour and microstructural changes of this alloy were measured and evaluated by various tests. Considering that the aim of this project is to identify the creep behaviour in the condition that the grains deviate from the ideal angle during directional solidification, first the grain structure was determined in casting samples, then their mechanical behaviour was investigated by determining the grain deviation. Also, numerical simulation was used to model the grain size of the cast samples. By three-dimensional modelling of grains in creep specimens and then changing the growth angle of dendrites in each grain, numerical analysis of the creep of the specimen using Norton equation and changes in creep life by changing the deflection angle of the grains was obtained. The results showed that increasing the angle of deviation during the growth in a grain from zero to 3 degrees caused a 0.4% increase in mean stress and increasing the growth angle in the same grain from 3 to 10 degrees, caused a 5% increase and an increase from 10 to 20 degrees caused an 11% increase in mean stress in this grain in the middle section of the sample.

In this study, the effect of melt holding times for 15, 30, and 45 minutes at superheating temperatures of 200, 250, and 300 °C on the phase of Mg2SiP, eutectic Mg2SiE, Al5FeSi, Al5Mg8Si6Cu2, Al2Cu, nucleation temperature of these phases, and the hardness of Al-20Mg2Si-2Cu composite were examined. Microstructural observations and quantitative analysis showed that the best modification was achieved at superheating of 300 °C and a holding time of 15 minutes. Compared with the reference sample with 100 ° C superheating, the dendritic and coarse morphology of Mg2SiP particles changed to the fine polyhedral. The average particle size decreased dramatically from 1179 to 255.5 μm. Particle area and aspect ratio decreased by 83% and 13%, respectively. The number of particles per unit area increased from 9 to 57. Superheating converted the needle β-Fe to the β α-Fe Chinese script, although no significant change in the features of the Mg2SiE, Al5Mg8Si6Cu2, and Al2Cu phases was observed. A good correlation was found between the nucleation temperature and the microstructural transformation of the Mg2SiP phase. After implementing superheating of 300 °C for 15 minutes, the nucleation temperature of the Mg2SiP phase increased from 647.3 to 664.4 °C. The superheating treated composites showed higher hardness than the reference specimen, regardless of temperature and time. The highest hardness was obtained with 82.1 Vickers, which could be attributed to increasing the number of particles and reducing the distance between particles.

محاسبه وزن مواد بار کوره های ذوب، با موازنه جرم عناصر آلیاژی مواد ورودی و خروجی انجام می شود. اما فرایند ذوب، پیچیدگی هایی دارد، که اغلب در محاسبات نادیده گرفته می شود، و باعث عدم اطمینان در وزن مواد بار، اصلاح چندباره ذوب، تأخیر در تخلیه، افزایش هزینه و کاهش کیفیت مذاب می شود. هدف پژوهش حاضر، توسعه مدلی است، که نه تنها وزن مواد اولیه برای ترکیب شیمیایی ذوب هدف را محاسبه و بهینه سازی کند، بلکه هدررفت ناهمگن عناصر آلیاژی، ناخالصی های غیرفلزی مواد بار، و اصلاح ذوب اولیه در کوره را نیز در نظر بگیرد. مقاله حاضر، فرمولاسیون یک مدل محاسبه بار کوره ی ذوب آلیاژ را ارایه می کند، که بر اساس موازنه جرم غیرخطی و بهینه سازی استاندارد توسعه یافته و همراه با یک الگوریتم حلقه ی تکرار برای حل عددی، ویژگی های موردنظر را برای ذوب تمام آلیاژها در برمی گیرد. برای ارزیابی مدل، یک مساله ذوب آلیاژ برنج با 7 عنصر آلیاژی و 8 نوع مواد بار در مقیاس صنعتی طرح و بررسی گردید. با حل مساله به کمک مدل توسعه یافته، کسر وزنی مواد اولیه، وزن و ترکیب شیمیایی ذوب اصلاح شده و کمترین هزینه مواد محاسبه گردید. مدل پیش بینی کرد که وزن کل مواد ورودی 9909 kg (همراه با ذوب اولیه)، هدررفت مواد معادل 262 kg، وزن نهایی مذاب اصلاح شده 9646 kg و بازدهی ذوب 97.3% باشد. تحلیل بهینه بودن جواب، تایید کرد که کمترین هزینه مواد به دست آمده است. مدل استاندارد غیرخطی، ابزاری سریع برای بهینه سازی هزینه و محاسبه بار کوره است که پتانسیل هایی برای کاهش هزینه و تسهیل اتوماسیون صنعتی فرایند ذوب ایجاد می کند.

Using a high quality, clean melt is a fundamental prerequisite for production of high-quality Al castings. So far, a variety of techniques have been suggested to increase the quality of cast Al alloys including, rotary degassing and the use of fluxes and ceramic foam filters during melt preparation and casting. While the dissolved hydrogen in molten Al alloys is considered as the main cause of the formation of pores and therefore, the low quality of cast aluminum alloys, the study of the literature in this paper demonstrates that hydrogen itself has almost no negative impact on the quality of these alloys. The present paper suggests that the sole factor that impairs their quality is the presence of oxide films and inclusions. Also, this paper suggests a practical procedure to evaluate the damages to cast Al alloys during the production steps that is based on the reduced pressure test and uniaxial tensile test.

The investment casting process is a reliable way to produce complex and delicate shapes , with good surface quality and high dimensional accuracy. The main advantage of investment casting is the ability to produce a wide variety of products from different industries, and non-machinable components can be cast in the same predetermined way, so that the final component generally does not need to be welded and assembled, thus saving time and money. This method was used in ancient times to produce weapons, jewelry and artistic sculptures. Over the centuries, this technology has advanced and is used in the casting of various works of art, industrial parts and the production of turbine blades. The present article is an overview of the application of investment casting process in the production of artistic pieces. In this article, investment casting history, model wax properties, adhesives, additives and fillers, ceramic shell fabrication process for non-ferrous alloys, comparison of microwave and autoclave dewaxing methods, smelting and final operations, 3D printing method for Model construction and finally the simulations used to predict defects and model optimization will be reviewed separately.