ANALYSIS OF TECHNOLOGICAL POSSIBILITIES OF TWO-CHAMBER IMPULSE DEVICES FOR SHEET STAMPING

Проведен анализ технологических возможностей двухкамерных устройств для листовой штамповки с одной и двумя камерами сгорания. В устройствах с одной камерой сгорания штамповка детали происходит в холодном состоянии заготовки под действием на нее гибкой среды за счет кинетической энергии поршня, ускоряемого продуктами сгорания газообразной топливной смеси. В устройствах с двумя камерами сгорания процесс штамповки совершается с нагревом заготовки воздействием на нее горячего газа, образованного при сгорании в верхней камере предварительно сжатой топливной смеси. При этом сжатие смеси осуществляется за счет энергии продуктов сгорания, образованных в нижней камере сгорания. Доказано, что устройства с одной камерой сгорания целесообразно использовать для штамповки из пластичных сортов сталей деталей разнообразной формы толщиной до 4 мм и из пластичных цветных сплавов толщиной до 8 мм. Устройства с двумя камерами сгорания целесообразно использовать для штамповки деталей из малопластичных сортов алюминиевых, титановых сплавов и других труднодеформируемых сплавов. Двухкамерные устройства для листовой штамповки обладают широкими технологическими возможностями и могут быть эффективно использованы в мелкосерийных производствах для штамповки деталей различной формы We carried out the analysis of technological capabilities of two-chamber devices for sheet stamping with one and two combustion chambers. In devices with one combustion chamber, the stamping process is carried out in the cold state of the workpiece by the action of an elastic medium on it, using the kinetic energy of the piston accelerated by the combustion products of the gaseous fuel mixture. In devices with two combustion chambers, the stamping process is carried out with the heating of the workpiece by the action of the hot gas formed during combustion in the upper chamber of the pre-compressed fuel mixture. In this case, the mixture is compressed due to the energy of the combustion products formed in the lower chamber. We established that devices with one combustion chamber are expedient to be used for stamping parts of various shapes with a thickness of up to 4 mm and from plastic non-ferrous alloys with a thickness of up to 8 mm from ductile steels. Devices with two combustion chambers are advisable to be used for stamping parts from low-plastic grades of aluminum, titanium alloys and other hard-to-deform alloys. Two-chamber devices for sheet stamping have wide technological capabilities and can be effectively used in small-scale production for stamping parts of various shapes

Role of Grain Size and Shape in Superplasticity of Metals

Superplasticity is characterized by an elongation to failure of >300% and a measured strain rate sensitivity (SRS), close to 0.5. The superplastic flow is controlled by diffusion processes; it requires the testing temperature of 0.5Tm or greater where Tm is the absolute melting temperature of metals. It is well established that a reduction in grain size improves the optimum superplastic response by lowering the deformation temperature and/or raising the strain rate. The low-temperature superplasticity (LTSP) is attractive for commercial superplastic forming, in view of lowering energy requirement, increasing life for conventional or cheaper forming dies, improving the surface quality of structural components, inhibiting quick grain growth and solute-loss from the surface layers, thus resulting in better post-forming mechanical properties. This paper will summarize the dependence of superplasticity on grain size and shape in various metallic materials, including ferrous and non-ferrous alloys, which has been considered as an effective strategy to enable the LTSP.

Application of cold gas dynamic spraying as an additive technology for producing materials based on nickel aluminide and titanium aluminide

Metal additive manufacturing is widely studied for its unique advantages over traditional manufacturing processes. It is used to form complex components of Ti, Fe or Ni alloys. However, for non-ferrous alloys – aluminum, magnesium, copper – additive technologies are not used due to rapid melting during laser, electron beam and/or arc treatment. Cold spraying is widely used as an effective technology for applying high quality coatings in the mass production of metal and alloy products and/or metal matrix composite coatings. In addition, cold spraying is a serious and effective tool for the additive manufacturing of metals, and research in this area is currently becoming intense. During heat treatment of materials obtained by cold spraying, new chemical compounds are formed – both intermetallic compounds and hardening ceramic inclusions that increase the microhardness. However, as a result of a change in the structure during chemical transformations, a change in the geometry of the product and the formation of pores can be observed.

Friction Stir Welding of Thick Plates of 4Y3Gd Mg Alloy: An Investigation of Microstructure and Mechanical Properties

Applications of non-ferrous light metal alloys are especially popular in the field of aerospace. Hence it is important to investigate their properties in joining processes such as welding. Solid state joining process such as friction stir welding (FSW) is quite efficient for joining non-ferrous alloys, but with thick plates, challenges increase. In this study, Mg alloy plates of thickness 11.5 mm were successfully welded via single-pass FSW. Due to the dynamic recrystallization, grain size in the stir zone was reduced to 16 µm which is ≈15 times smaller than the parent material. The optimized rotational speed and traverse speed for optimum weld integrity were found to be 710 rpm and 100 mm/min, respectively. A sound weld with 98.96% joint efficiency, having an Ultimate Tensile Strength (UTS) of 161.8 MPa and elongation of 27.83%, was accomplished. Microhardness of the nugget was increased by 14.3%.

Investigation of technology schemes for the production of cast composite functional materials

Obtaining and using ligatures, modifiers and deoxidizers to obtain structural alloys of a given composition and properties in metallurgy and foundry is an important production task. One of the existing developments in the field of technologies for the preparation of functional composites on a matrix basis for non-ferrous and ferrous alloys is the combination of solid filler with a melt of an active metal binder. At that, from the filler material, which is selected from the group comprising iron, nickel, titanium, silicon, boron, manganese, first a porous workpiece of a given geometric shape with a technological total pore volume is formed, then it is heated to a temperature corresponding to the liquidus temperature of the active binder, the heating being carried out in a gas inert medium, after which the heated workpiece is impregnated with the melt of this binder by forced infiltration of the melt into the pores of the workpiece under pressure, mainly by the method of liquid stamping. The task of the study was to expand the scope of use of composites, to create a single flexible universal, and at the same time, simplified technology that will provide an opportunity to obtain a wide range of diverse in composition and service characteristics of deoxidizers, modifiers and ligatures for non-ferrous and ferrous alloys. The developed technology, based on vacuum impregnation (suction) of the matrix alloy through porous filler, makes it possible to obtain new functional metal-matrix composite materials of a given composition for use as inexpensive ligatures, modifiers and deoxidizers in metallurgical processes, as well as to simplify and make their use safe. The proposed method for obtaining ligatures, modifiers and deoxidizers provides a possibility of their industrial serial production and is easy to perform, and also reduces the cost of the metallurgy product obtained with their application by increasing the effective content of active components and their more complete assimilation, which reduces the consumption of scarce and expensive materials.

Strong and ductile Fe-24Mn-3Cr alloy resistant against erosion-corrosion

The ternary-based Fe-24Mn-3Cr alloy has superior mechanical properties based on an attractive combination of high strength and ductility, with long-term environmental stability in highly corrosive environments compared to conventional ferritic steel alloys. This study reports that the environmental instability caused by the rapid electrochemical corrosion kinetics on the surface of conventional high Mn-bearing ferrous alloys could be overcome by a combination of high Mn–low Cr-balanced Fe and their synergistic interactions. In contrast to Cr-free Mn-bearing alloys, the high Mn–low Cr-bearing alloy showed comparatively lower corrosion kinetic parameters, without a continuously increasing trend, and higher polarization resistance according to electrochemical polarization and impedance spectroscopy measurements. Moreover, the rate of degradation caused by erosion–corrosion synergistic interaction under erosion–corrosion dynamic flow conditions was the lowest in the high Mn–low Cr-bearing alloy. These surface-inhibiting characteristics of the alloy were attributed primarily to the formation of a bilayer scale structure consisting of inner α-Fe2−xCrxO3/outer FexMn3−xO4 on the surface.

Production of TiC-MMCs Reinforcements in Cast Ferrous Alloys Using In Situ Methods

This literature review aims to summarize the research conducted on the production of locally reinforced ferrous castings based on metal matrix composites reinforced with TiC (TiC-MMCs). One way to improve the wear resistance of cast components is to reinforce critical regions locally with metal matrix composites (MMCs) without changing the toughness of the component core. The in situ method of self-propagating high-temperature synthesis is one of the main approaches for the production of this enhanced material. Using this approach, the reinforcement is formed from a powder compact inserted in the mold cavity. The temperature of the liquid metal then produces the combustion reactions of the powders, which promote the formation of the ceramic phase. This paper focuses on eight powder systems used to synthesize TiC: Ti-C, Ni-Ti-C, Ni-Ti-B4C, Fe-Ti-C/Fe-Cr-Ti-C, Cu-Ti-B4C, Al-Ti-C, and Al-Ti-B4C, and provides an overview of the methodologies used as well as the effect of processing variables on the microstructural and mechanical characteristics of the reinforcement zones.