No abstract

No abstract

In the foregoing years, micro components were frequently employed in various sectors such as the electronics and medical industry. In order to produce these components in large amounts and satisfying quality, the production processes have to be improved constantly. Heat treatment represents a critical step in the production chain of micro components, since it can either soften the foils for micro forming or increase the hardness of the micro components after the cold forming process, provided those are made of hardenable materials. In the investigated Al–Zr alloy, the formation of small primary Al3Zr precipitations results in a considerable improvement of the material's hardness. However, the presence of precipitations in the Al–Zr foils drastically limits the formability. Additionally, the precipitations are nearly not avoidable in the casting of the raw material and irreversible due to the limited solubility of zirconium in aluminum (0.28 wt%) close to the melting point of the aluminum solution. To overcome this problem, magnetron sputtering was employed to fabricate zirconium supersaturated Al–Zr foils by taking advantage of a low substrate temperature (below 50 °C). In particular the plasma power seems to influence the aging behaviour of sputtered Al–Zr foils.

This article discusses the distortion behavior during heating of bearing rings produced by cold rolling. The residual stress relaxation was characterized intensively and correlated to the distortion behavior. In the initial state, the rings show compressive residual stresses in tangential and axial direction with almost no variations along the circumference. Because of the cold-rolling process, the entire cross section is affected by residual stresses. The rings present a characteristic size change between the soaking temperatures 773 K and 823 K (500°C and 550°C), which can be correlated with the macroresidual stress relaxation in the core of the rings. Changes in roundness deviation were found, but the amplitude of oval and triangular shape increases continuously until austenitizing temperature is reached. As the macrostress relaxation is already completed at 873 K (600°C), another mechanism should be responsible for these distortions. A correlation between amplitude of the oval shape and decrease of full width at half maximum seems to be present. This may indicate that inhomogeneous recrystallization happens along the circumference of the rings. A triangular shape may result from the influence of the loading tool used as rings are positioned on three contact points during the stress relief treatment.

Thin sheets (20 µm - 30 µm) of an aluminum-scandium alloy were manufactured by magnetron sputtering with a homogeneous thickness distribution. The influence of bias voltage on the sheet properties was investigated. Steel sheets of 100 µm were employed as substrate and were coated in a dc magnetron sputtering unit fitted with a rectangular target of aluminum 2.0 w% scandium master alloy. After deposition, the substrates were dissolved in an oxidizing medium and thus freestanding aluminum-scandium thin films were obtained. The homogeneous thickness was achieved by a reciprocal movement of the substrate. The influence of a radio frequency bias voltage on the coating properties was investigated. The bias voltage resulted in an important coarsening of the columnar structure as well as an increase of the roughness and hardness. Additionally, a low bias voltage could intensively reduce the coating defect density without altering too much the sheet properties