B. Leszczyńska-Madej

Analysis of Extrusion Welding Conditions for AlMg Alloys with High Mg Content

In the work, an original method and a special modified device is presented enabling to determine welding conditions of hard deformable aluminium alloys. The main advantage of the proposed method is that it simulates conditions occurring in the welding chamber of the porthole dies. The weldability tests were performed for 5754 (3,5% Mg) and 5019 (5,5% Mg) alloys, in a wide range of temperatures and pressures. The microstructure and joints strength were examined. The welding conditions of AlMg alloys that allowed obtaining high-quality joints were determined. The obtained welding stress values will be the basis for extrusion porthole die design.

The Influence of Process Parameters on Microstructure and Mechanical Properties of PM Al+4 wt. %Cu Alloy

Attempts have been made to describe the influence of the process parameters, such as compaction pressure and sintering atmosphere on the microstructure and properties of PM Al4Cu alloy. Homogenous mixtures of Al4Cu elemental powders were achieved by tumbling powders for 30 minutes in the Turbula T2F mixer. The powders were subsequently cold compacted under pressures of: 200MPa, 300MPa and 400MPa in a rigid die on a single action press. The green compacts were sintered in two different atmosphere - nitrogen and vacuum at 600°C for one hour. After that, the samples sintered in nitrogen atmosphere were re-pressed and re-sintered (2p2s) under the same conditions. The green compact and as-sintered densities were measured using the geometric method. Additionally, the Brinell hardness and the bending strength in three point bend test were determined. The microstructure of the samples was also analyzed using both the light microscopy (LM) and scanning electron microscopy (SEM).The obtained results show, that optimal pressing pressure is 300MPa. Increasing pressure to 400 MPa has not a substantial effect on increase of the final sample density. Therefore applying higher compaction pressure (over 300MPa), from the economical point of view, is unnecessary.

Selection of Protective Coatings Obtained by Plasma Spraying Method for Foundry Industry

The paper presents the results of studies of protective coatings for graphite moulds, which were used in copper casting process. The following coatings were involved: Mo, NiAl, NiCrAl, Cr3C2-NiCr, WC-CrC-Ni. All tested coatings were applied on the graphite substrate by plasma spraying method. The microstructure was investigated by optical microscopy (OM) and scanning electron microscopy (SEM). The microhardness of coatings was measured by Vickers method. The wettability of coatings by liquid copper was evaluated. It was found that NiAl and NiCrAl coatings had the highest limiting wetting angle and consequently the lowest wettability among all the examined coatings. It was also found that chemical composition strongly influenced the coating properties.

Effect of the Addition of Glassy Carbon on the Structure and Properties of ZrO2-Y2O2 Coatings

The effect of the addition of glassy carbon on the structure and properties of ZrO2-Y2O2 coatings deposited at the graphite substrate has been investigated. The coatings were deposited by plasma spraying method in an industrial company Plasma System SA Silesian Siemianowice using MIM40 equipment. The microstructure of coatings was investigated by light microscopy (MO), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Abrasion was carried out with the use of tribological tester Ducom by pin-on-disc method. The results of investigations showed that the addition of the glassy carbon into coatings materials has increased microhardness and resistance against the wear.

Bulk Nanomaterials and Powders Consolidation Produced by Cyclic Extrusion Compression

The Cyclic Extrusion – Compression - reciprocating extrusion process (CEC) is one of severe plastic deformation methods (SPD), which allow to produce bulk nanomaterials without changing the initial shape of deformed samples. The results are presented showing that the average grains size and microbands thickness in aluminium alloys decrease below 100 nm. The investigations revealed that the average grains size is about 250 nm and 200 nm in polycrystalline and monocrystalline copper, respectively.The Cyclic Extrusion Compression method is also used to produce bulk materials by powder consolidation. The subgrains/nanograins inside the silver powder particles after the consolidation processes achieved the mean size of about 100 nm. Moreover, it has been found that inside structure observed by TEM, the consolidated powder granules consisted from nanometric twins of about 10 – 20 nm. This silver based powder consolidated by CEC method were extruded by hydrostatic extrusion method. The final product were the wires with a diameter of 3 mm, which were used to electrical contacts production.

Processing of Copper by Equal Channel Angular Pressing (ECAP) – Microstructure Investigations

The present study attempts to apply Equal-Channel Angular Pressing (ECAP) to 99.99% pure copper. ECAP process was realized at room temperature for 4, 8 and 16 passes through route BC using a die having angle of 90°. The microstructure of the samples was investigated by means both light and transmission electron microscopy. Additionally the microhardness was measured and statistical analysis of the grains and subgrains was performed. Based on Kikuchi diffraction patterns misorientation was determined. There were some different types of bands in the microstructure after deformation. The shear bands, bands and in the submicron range the microshear bands and microbands are a characteristic feature of the microstructure of copper. Also characteristic was increasing of the number of bands with increasing of deformation and mutually crossing of the bands. The intersection of a bands and microbands leads to the formation of new grains with the large misorientation angle. The measured grain/subgrain size show, that the grain size is maintained at a similar level after each stage of deformation and is equal to d = 0.25 – 0.32 μm.