The Effect of Cold Swaging of Tungsten Heavy Alloy with the Composition W91-6Ni-3Co on the Mechanical Properties

The paper presents the results of studies on the effects of heat treatment and cold-work parameters on the mechanical properties and microstructure of the tungsten heavy alloy (WHA) with the composition W91-6Ni-3Co. Tungsten heavy alloy (WHA) is used in conditions where strength, high density, and weight are required. The material for testing as rod-shaped samples was produced by the method of powder metallurgy and sintering with the participation of the liquid phase and then subjected to heat treatment and cold swaging. The study compares the effect of degree deformation on the strength, hardness, microhardness, and microstructure of WHA rods. The conducted tests showed that heat treatment and cold-work allowed to gradually increase the strength parameters, i.e., tensile strength , yield strength , elongation ε, hardness, and microhardness. These processes made it possible to increase the tensile strength by over 800 MPa (from the initial 600 MPa after sintering to the final value of over 1470 MPa after heat treatment with cold swaging deformation with reduction of 30%) and the hardness from 32 to 46 HRC.

Investigation of Mechanical and Microstructural Properties of Welded Specimens of AA6061-T6 Alloy with Friction Stir Welding and Parallel-Friction Stir Welding Methods

The present study investigates the effect of two parameters of process type and tool offset on tensile, microhardness, and microstructure properties of AA6061-T6 aluminum alloy joints. Three methods of Friction Stir Welding (FSW), Advancing Parallel-Friction Stir Welding (AP-FSW), and Retreating Parallel-Friction Stir Welding (RP-FSW) were used. In addition, four modes of 0.5, 1, 1.5, and 2 mm of tool offset were used in two welding passes in AP-FSW and RP-FSW processes. Based on the results, it was found that the mechanical properties of welded specimens with AP-FSW and RP-FSW techniques experience significant increments compared to FSW specimens. The best mechanical and microstructural properties were observed in the samples welded by RP-FSW, AP-FSW, and FSW methods, respectively. Welded specimens with the RP-FSW technique had better mechanical properties than other specimens due to the concentration of material flow in the weld nugget and proper microstructure refinement. In both AP-FSW and RP-FSW processes, by increasing the tool offset to 1.5 mm, joint efficiency increased significantly. The highest weld strength was found for welded specimens by RP-FSW and AP-FSW processes with a 1.5 mm tool offset. The peak sample of the RP-FSW process (1.5 mm offset) had the closest mechanical properties to the base metal, in which the Yield Stress (YS), ultimate tensile strength (UTS), and elongation percentage (E%) were 76.4%, 86.5%, and 70% of base metal, respectively. In the welding area, RP-FSW specimens had smaller average grain size and higher hardness values than AP-FSW specimens.

Laser Butt Welding of Thin Ti6Al4V Sheets: Effects of Welding Parameters

Titanium and its alloys, particularly Ti6Al4V, which is widely utilized in the marine and aerospace industries, have played a vital role in different manufacturing industries. An efficient and cost-effective way of joining this metal is by laser welding. The effect of laser power and welding speed on the tensile, microhardness, and microstructure of Ti6Al4V alloy is investigated in this paper. Results show that the microhardness is highest at the fusion zone and reduces towards the base metal. The microstructure at the fusion zone shows a transformed needle-like lamellar α phase, with a martensitic α’ phase observed within the heat affected zone. Results of tensile tests show an improved tensile strength compared to the base metal.

Influence of Machine Type and Powder Batch During Laser-Based Powder Bed Fusion (L-PBF) of AISI 316L

The use of additive manufacturing (AM) in industrial applications is steadily increasing due to its near net shape production and high design-freedom. For metallic components, laser-based powder bed fusion (L-PBF) is currently one of the most widely used AM processes. During L-PBF, a component is manufactured layer by layer from a powdery raw material. The process is controlled by a multitude of parameters like the laser power, scanning speed and layer thickness, whose combination significantly influences the properties of the components. In this study, the influence of the L-PBF machine type and the influence of the powder batch are investigated by means of relative density, microhardness and microstructure of the components. For this purpose, three setups are defined, differing in the powder batch and machine type used. By comparing the process results of the additive manufacturing of different setups, the influence of the machine type and powder batch are determined. The considered material is stainless steel AISI 316L. The results revealed significant differences between all investigated properties of the additively manufactured components. Consequently, process parameter combinations cannot be transferred between different machine types and powder batches without verification of the component properties and, if necessary, special adaption of the process.

Effects of rapid conductive heating and passive cooling with cold dies on hot-forming formability and final mechanical properties of boron steel sheets

This paper is focused on the assessment of hot-forming limits and post-process properties of the 22MnB5 steel sheets heated to 950°C using rapid conductive heating, which is proposed as a fast and efficient method. An experimental axisymmetric bulging die set appropriate for conductive heating was designed and manufactured. Stretch-forming tests were conducted on rectangular specimens with three different widths until failure using dies at room temperature. The die set at room temperature performed passive cooling as well as deformation. The tests showed the limits of formability. Microhardness and microstructure analyses of the formed steel proved the bainitic–martensitic nature obtained at the end of the process. The results show good agreement with the published data collected by conventional furnace heating, which is a slower and more inefficient process.

Effect of sintered electrode on microhardness and microstructure in electro discharge deposition of magnesium alloy

In this study, an endeavour have been made to depositing the electrode materials over the surface of the magnesium alloy using electrical discharge machining (EDM) with WC-Cu powder compacted sintered electrode. Various process parameters such as compaction load, discharge current and pulse on time are selected to carry out the experiment in order to attain the maximum material migration rate (MMR) or deposition rate and microhardness (MH). It was concluded that the MMR and MH increased with increase in discharge current and pulse on time at low compacted electrode but it is decreased at lower discharge current and pulse on time. Highest MMR and MH were attained successfully at partial sintered low compaction load electrode. Microstructure evaluation has been carried out on deposited surface using scanning electron microscopy (SEM) and presence of electrode element in the deposited surface was confirmed by energy dispersive spectroscopy (EDS). Defects mechanism such as globules and craters are formed during EDC with high current and pulse on time respectively, which diminishes the surface roughness. It was observed that the compaction load is the influence parameter on the MMR and MH.

Assessment of Applicability of the MPF-4 Magnesium Powder for Manufacturing Parts Using 3D Printing Technologies

The article provides study results for two samples manufactured with the MPF-4 magnesium powder by means of directed laser energy and material deposition. The authors studied microhardness and microstructure of the samples by means of optical and electronic microscopic techniques; provided results of the impact of annealing on microstructure and microhardness of the samples; and assessed the possibility of using the MPF-4 powder for manufacturing parts using 3D printing technologies.

Milling Microchannels in Monel 400 Alloy by Wire EDM: An Experimental Analysis

This paper presents the results of an investigation on the capacity of wire electrical discharge machining (WEDM) to produce microchannels in the Nickel-based alloy, Monel 400. The main objective of the current study is to produce microchannels with desired/target geometry and acceptable surface quality. Square cross-sectional microchannels with dimensions of 500 × 500 µm were investigated. Experiments were conducted based on the one-factor-at-a-time approach for the key input WEDM process parameters, namely pulse-on time (TON), pulse-off time (TOFF), average gap voltage (VGAP), wire feed (WF), and dielectric flow rate (FR). Dimensional accuracy, machining speed, surface roughness, surface morphology, microhardness, and microstructure were analyzed to evaluate the microchannels. The minimum errors of 6% and 3% were observed in the width and depth of the microchannels, respectively. Furthermore, microchannels with enhanced surface integrity could be produced exhibiting smooth surface morphology and shallow recast layer (~0–2.55 µm).

e EFFECT OF ?-Al2O3 NANOPARTICLES ADDITION ON SOME PROPERTIES OF CoCrMo ALLOY FABRICATED BY POWDER METALLURGY ROUTE

CoCrMo alloys are used as biomaterial due to their good corrosion and wear resistance, with reasonable biocompatibility. The present study aims to investigate the effect of (1, 3 and 5) wt% ?-Al2O3 nanoparticle additions on some properties of pre-alloyed CoCrMo when fabricated by powder metallurgy route. The density, porosity, microhardness and microstructure of the fabricated samples were examined. The results revealed that the addition of ?-Al2O3 nanoparticle has a distinguished effect on the density of sintered CoCrMo alloy samples, where continues increase in the porosity was happened and reached to its maximum value at the higher addition amount. While the density showed an inverse trend to that of the porosity with the increasing of the nanoparticle addition. The microhardness was decreased as the amount of the nanoparticle addition to CoCrMo alloy was increased. The microstructure observation by SEM and SEM-Mapping is revealed the partial isolation of CoCrMo particles by the nanoparticle additions and it was associated with the formation of passive Cr2O3 oxide. In turn the XRD analysis depicted the co-existence of ?-Co and ?-Co phases besides, the Cr2O3 oxide. Although the increased porosity with the nanoparticle addition but, this will perhaps, increase the tissue ingrowth when the fabricated nanocomposites were utilized as biomaterial