Physikalische Eigenschaften von CuNi 10 Fe 1 Mn und CuNi 30 Mn 1 Fe unter besonderer Berücksichtigung des Ausscheidungsverhaltens

Influence of Precipitation Process on the Physical Properties of the Cu? Ni-Alloys CuNi 10 Fe 1 Mn and CuNi 30 Mn 1 Fe The following physical properties were measured on six heats of CuNi 10 Fe 1 Mn and seven heats of CuNi 30 Mn 1 Fe: density, Young's modulus, Poisson's ratio, thermal expansion, specific heat capacity, electrical resistivity, thermal conductivity, thermal diffusivity, thermoelectric voltage, saturation magnetization and magnetic permeability. In addition the variation of the values within different heats and different specimens were evaluated. The influence of precipitates varied depending on thermal treatment. The measurement of electrical resistivity and the magnetic properties are useful to evaluate the thermal treatment of CuNi 10 Fe 1 Mn especially after rapid cooling.     

Einfluß des ZrO2-Zusatzes auf mechanische Eigenschaften und den ungeschmierten Gleitverschleiß von TiB2-ZrO2-Mischkeramiken

Effect of ZrO₂ addition on mechanical and tribological properties of TiB₂-ZrO₂-composites TiB₂-ZrO₂-composites were produced by hot-pressing in argon. The mechanical and tribological properties of the composites were investigated in relation to the amount and the type of the ZrO₂ added. Addition of ZrO₂ reduced the sintering temperature of the TiB₂-ZrO₂-composites and led to growth inhibition of the TiB₂ phase. ZrO₂ also increased the bending strength and fracture toughness of the composites. Tribological tests were carried out using laboratory tribometers under unlubricated oscillating sliding contact against Al₂O₃-, Si₃N₄- and SiC-counterbodies. Abrasive wear of the ceramics against 80 mesh SiC grits was studied by using an abrasive wheel test. During sliding contact the composites showed high wear resistance but caused extensive wear of the counterbodies and high friction coefficients compaired to self-mated monolithic Al₂O₃- and ZrO₂-ceramics. Volumetric wear loss of the TiB₂-ZrO₂-composites due to abasive SiC grits was by a factor up to 30 lower than that of a commercial monolithic Al₂O₃. Wear resistance of the composites increased with decreasing amount of ZrO₂ and was higher for the composites with addition of partially stabilized tetragonal ZrO₂ than for those with addition of monoclinic ZrO₂.     

Einfluß des Richtens auf das mechanische Verhalten von Federlegierungen

Influence of Levelling Processes on the Mechanical Behaviour of Spring Alloys Levelling processes – that means straightening of wire or level rolling of strip – have an impairing effect on the R_p0,2 and R_p0,1 proof strength of cold worked spring alloys and on the hysteresis behaviour of flat springs respectively. SEM and TEM investigations indicate that recovery is initiated by levelling processes and is intensified by a subsequent age hardening treatment. This may lead to a modification of age hardening behaviour and effectivity for those alloys which show different age hardening mechanisms in the cold worked and recovered state respectively. The detrimental influence of level rolling on the hysteresis behaviour is found to be due to an increased subgrain size after age hardening treatment. The results show that improvement of geometry by levelling processes is only possible at the cost of decreased spring properties.     

Einfluß der Korngröße auf mechanische Eigenschaften und den ungeschmierten reversierenden Gleitverschleiß von Al2O3-Keramik

Influence of grain size on mechanical properties and dry oscillating sliding wear of Al₂O₃-ceramics Specimens with average grain sizes varying between about 0.8 μm and 12 μm were produced by cold isostatic pressing of high purity Al₂O₃-powder followed by sintering between 1300°C and 1700°C. Hardness, Young's modulus, bending strength and fracture toughness were measured as a function of average grain sizes. Tribological tests were carried out on the different microstructures at normal laboratory air and room temperature by using a ring-on-block tribometer. Experimental results showed the dependence of mechanical properties on grain size, hardness and bending strength obeying a Hall-Petch type relation, approximately. Coefficient of friction was relatively independent of grain size under the test conditions used. However, wear intensity increased substantially if a critical grain size was surpassed. This was due to a change in mechanisms of material removal which was confirmed by scanning electron microscopical studies of the worn surfaces.     

Kontaktwerkstoffe auf Silberbasis ‐ Gefüge und mechanische Eigenschaften

Silver‐based contact materials – microstructure and mechanical properties Different silver‐based materials have been used in relays and contactors. Silver‐based composite materials in particular have played an important role. To produce such composite materials on an industrial scale, conventional powder mixing and wet‐chemical methods are used. By means of the powder‐metallurgical route, these materials are processed in a second step into wire material. To produce silver‐based composite materials with a comparable microstructure, the usability of alternative production routes was tested. This article shows the potential of the methods high‐energy ball milling (HEM) and intensive mixing compared to the two above‐named conventional methods. The main focus is on the evaluation of the microstructure of the composite powder and the extrusion wires concerning the dispersion of the reinforcement component and the resulting mechanical properties of the wire material.     

Einfluß der Mahlbedingungen und der Qualität der Ausgangsprodukte auf die Eigenschaften von Al-C-Strangpreßprodukten

Influence of the Crinding Parameters and the Quality of the Starting Materials on the Properties of Extruded AIC Products Dispersion strengthened aluminium has been produced by grinding aluminium powder with carbon black in a high energy ball mill, heat treating of the milled powder and subsequented hot extrusion. Tensile strength, elongation, hardness and impact strength were determined. The influence of griding parameters, such as duration, speed of rotation of the rotation arm and the weight ratio of powder to milling balls on the mechanical properties of the extruded rods were investigated. Other important variables are the oxygen content of the aluminium powder, the quality of the carbon black and additions of control agents such as oil or water.     

Über den Einfluß unterschiedlicher Abscheidungsbedingungen auf einige mechanische Eigenschaften von Nickelschichten aus dem Sulfamatbad

Conditions of nickel-plating from a sulfamate electrolyte and mechanical properties of the deposit . Nickel deposits are used for decorative and technical application. In this paper the influence of plating conditions on internal stress, hardness, fatigue and corrosion resistance of nickel deposit is dicussed.     

Der Einfluß der Feuchteaufnahme auf die mechanischen Eigenschaften von Phenoplasten

The Effect of Moisture on the Mechanical Properties of Phenolic Moulded Materials In order to use thermosetting moulding material it is necessary to know how the mechanical properties are changed by absorption of water. Therefore, multiphase systems based on phenolic resin, with varying quantities of wood flour and/or powdered minerals as fillers, were examined. The relationship between moisture absorption and the change in Young's modulus, flexural strength and the strain of the outer fibre at fracture was determined. It could be shown that the increase in flexural strength as water absorption began is a result only of the swelling stress.     

Sinterwerkstoffe für elektrische Kontaktstücke der Energietechnik und ihre Eigenschaften

Sintered Materials for Electric Contacts in Power Engineering and their Properties . In the field of electric contacts the task of material development lies in optimating of contact properties e. g. weld strength, erosion and contact resistance. Included is a survey of the systems of metal-metal, metal-metal compound and metal-metaloid including examples for base metals and additives. Knowledge of weld strength and erosion by arcing are necessary besides physical properties and structure for selecting contact materials. The properties mentioned have been measured by WATE (welding-arc erosion-test-equipment). The values of the weld strength are presented as cumulative frequency plottings. Joining-technique of contact and supporting metal is of special importance. A reliable connection is obtained by two-layer-contacts. Changes of structure caused by arcing are described; for example contacts from AgNi40, WCu30 and AgCdO12. Both, construction and modern contact materials have helped to increase the capacity of contactors and switches as well as the reliability.     

Einfluß der Probengröße auf die bruchmechanischen Eigenschaften von Sinterstahl

Influence of Specimen Size on the Fracture Mechanical Behaviour of Sintered Steel Fracture mechanics testing was carried out with small and big specimens using high-temperature sintered Fe-2%Cu-2.5%Ni-alloys in the densities of ρ = 7.1 and 7.4 g/cm³. These steels are often used in the manufacturing of PM-parts. Due to the different dismensions the crack propagation is for the bigger sizes faster than for the smaller sizes. Also the conditional fracture toughness of the big specimens is superiour to the toughness of the small specimens. But under consideration of a plain strain state for the big specimens and of a plain stress state for the small specimens valid fracture toughness values being independent from the specimen size can be calculated applying linear-elastic fracture mechanics. These results were obtained for both densities investigated. The increase of the density delivers principally better fracture mechanical data. Hereby the relation of strength data with the microstructure is also discussed.     

Einfluß der Wärmeermüdung im Tieftemperaturbereich (77 K ⇔︁ 373 K) auf mechanische Eigenschaften der (α + β)-Ti-Legierung

Effect of the low-temperature thermal cycling (77 K ⇔︁ 373 K) on certain mechanical properties of a two-phase (α + β)-titanium alloy The paper reports an investigation on the effect of low-temperature thermal cycling (LTTC) within (77 K ⇔︁ 373 K) range on select mechanical properties and crystal lattice parameters of the constituent phase, α and β, of a double-phase titanium alloy as determined at temperatures of 295 K and 77 K. Fatigue tests were conducted under plane bending conditions at stresses exceeding the material endurance limit. It was found that the LTTC effects were closely related to the number of thermal cycles applied: after 100 cycles the fatigue strength at the two temperatures rose by 30% as compared with the no-LTTC condition: after 500 LTTC cycles a pronounced drop in the fatigue strength was observed ′ 87% at temperature of 295 K and 30% at 77 K. Microscopy and X-Ray studies showed that twinning had a significant effect on both the LTTC and mechanical fatigue processes. Residual stresses arising during the LTTC treatment were found to be a stimulating factor in the development of deformational processes occurring in the loaded material.     

Der Einfluß der Porosität auf einige Eigenschaften von Wolfram/Kupfer-Kontaktwerkstoffen

The Influence of Porosity on a Few Properties of Tungsten/Copper Contact Materials . An investigation has been carried out on the influence of the amount of residual porosity on the electrical and mechanical properties of infiltrated tungsten/copper materials. By means of adding different quantities of infiltrating metal materials with a tungsten content of approximately 70 wt.% containing between 0,2 and 30% pores were produced. The following properties were measured for the different material specimens: are erosion rate, electrical conductivity, Vickers hardness number, and notch impact toughness. The arc erosion rate is not noticeably increased by pore contents up to 4%, all the other properties, however, are influenced considerably even by the smallest amount of measurable residual porosity. Thus it has to be concluded that infiltration with a slightly smaller quantity of infiltrating metal than that necessary to attain a pore-free material – a technique used occasionally in order to avoid the necessity of finishing the infiltrated parts – will lead to changes in quality.     

Einfluß der Temperatur und der Umgebungsbedingungen auf das Ermüdungsverhalten metallischer Werkstoffe

Influence of Temperature and Environmental Conditions on Fatigue Behaviour of Metallic Materials The corrosion fatigue behaviour of metallic materials is influenced by environmental conditions. With increasing temperature a similar diminishing of fatigue strength can be observed as in the usual tensile properties. Air and water vapour decrease the number of cycles to fracture because they accelerate the crack propagation by adsorptive and reactive processes at the crack tip. By the effect of pure hydrogen or hydrogen sulfide and mixtures from both appears a marked increasing of crack propagation rate in fracture-mechanical test pieces alternating loaded at low frequency (1 Hz). Corrosive mediums influence also the formation of cracks. A mechanical electrochemical failure mechanism leads to a total loss of fatigue strength. Depending on performance of materials in an aggressive solution active or passive corrosion fatigue occurs. With regard to the form of appearance the two kinds differ in characteristic manner.     

Einfluß des Festwalzens auf die Oberflächen‐ und Randzoneneigenschaften der Magnesiumlegierungen AZ31 und AZ91

Influence of burnishing operations on surface‐ and subsurface properties of AZ31 and AZ91 A mechanical surface treatment on magnesium‐alloys can be used to improve surface and subsurface characteristics after the cutting process. Investigations show, that the grooves, resulting from the turning process, are planed. The hardness of the surface rises. Compared to turned and polished samples, the increased strength and the induced residual stress of burnished samples cause an increased fatigue strength under rotating bending stresses. The corrosion resistance of AZ31 is enhanced by roller burnishing.     

Einfluß der Hartstoffkomponenten auf einige Eigenschaften von Hartmetallen unter besonderer Berücksichtigung neuerer Werkstoffentwicklungen

Influence of the Hard-material-components on some Properties of Hardmetals Respecting Especially Modern Developments of Working Materials . In the following paper some properties of hardconcerning the application are discussed. First of all the function of tungsten-carbide, of titanium-carbide and of tantalum-carbide in the conventional hardmetals are described, also pointing out the possibilities of linear-analytical structure-examination in connection with tool-life-tests Also the field of special working-materials with carbide phase used nowaday in the market besides conventional carbide-base hardmetals is reported briefly.     

Der Einfluß der Haupt- und Seitenkerbung auf die Temperaturabhängigkeit der Kerbschlagarbeit

The effect of main notch and of side grooves on the temperature dependence of the absorbed energy in impact tests Charpy impact tests were performed on test pieces having different radii of curvature of base of main notch. Six series were sidegrooved and six series were without side grooves. The fracture mechanisms and the appearance of the fracture surfaces are discussed. It is shown that the common practice to assign lower shelf, transition range, and upper shelf in the absorbed energy-temperature curve to cleavage fracture, mixed fracture, and fibrous fracture is not always valid. Cleavage fracture may occur in the entire transition range and mixed fracture may take place in the upper shelf.     

Der Einfluß der Kohlenstoff-Diffusion auf die mechanisch-technologischen Eigenschaften von ferritisch-austenitischen Schweißverbindungen im Chemie-Betrieb

The effect of carbon diffusion on the mechanical properties of ferritic-austenitic weldments . Weldments between ferritic and austenitic steels indicate a diffusion of carbon from ferritic to austenitic partner as an influence of temperature stresses and due higher solubility of carbon in γ-iron in comparison to α-iron. Investigations on two characteristic weldments (German standard H II/1.4571 and H II/Ni) have been conducted in different annealed conditions to study the effect of carbon diffusion on the various mechanical properties. There is an observable impairement of the mechanical properties of the weldments. Increased hardness in the carburised zone causes cracking and tensile strength as well as notch toughness decrease in the decarburised area.     

Einfluß einer thermomechanischen Behandlung auf die mechanischen Eigenschaften der Ti6Al4V-Legierung

Influence of thermomechanical treatment on the mechanical properties of Ti6Al4V Thermomechanical treatments of Ti6Al4V including deformation just below the β-transus followed by water quenching and aging were shown to substantially improve the mechanical properties. Especially the fatigue strength was raised well beyond levels known from conventional processed material, for both room and elevated temperatures. The paper shows how other properties like tensile strength, ductility, fracture toughness, creep strength fatigue crack growth and stress corrosion cracking are affected.