Mit Lichtmikroskopie, EPMA, TEM und Elektronenbeugung wurde das Ausscheidungsverhalten von Cu – Ag-Legierungen untersucht. Insbesondere werden dabei der Charakter der kontinuierlichen Vorentmischung ...und die Gefügeausbildung im Anfangsstadium der Entmischung sowie zwei unterschiedliche diskontinuierliche Ausscheidungsarten beschrieben. Zu Beginn der Auslagerung konnte ein metastabiler Zustand der silberreichen Entmischungszonen als erstes von drei typischen Entmischungsstadien der kontinuierlichen Ausscheidung beobachtet werden. Die Ausscheidungsvorgänge zeigen starke Abhängigkeit vom Silbergehalt der Legierung: Bei höherem Ag-Gehalt wird die Entmischung beschleunigt. Für die beiden diskontinuierlichen Ausscheidungen ist ein kritischer Übersüttigungsgrad des Mischkristalls erforderlich.
Alloys of the quasibinary section Cu –NiBe were experimentally investigated with differential thermal analysis, optical microscopy, electron microanalysis, transmission electron microscopy and X-ray ...diffraction. The construction of the quasibinary Cu–NiBe phase diagram was made based on the experimental results. The constitution of alloys of the whole section was studied along with the investigation of the microstructure and crystallographic relationship of the NiBe phase in aged alloys from the Cu-rich corner of the Cu–NiBe system.
The evolution of the chemical and phase composition of carbide precipitates in X20CrMoV12.1 steel after longterm service of 56 000 θ (470 – 530 °C at up to 18MPa) and after heat treatment (650 and ...800 °C) was investigated using transmission electron microscopy and Auger electron spectroscopy. The precipitates found were mostly of M
type, the S- and v-phase and traces of M
C. In service loaded state the presence of M
precipitates was also established. The evolution sequence is obviously M
C → M
!M
The constitution of alloys and the liquidus surface in the Al-rich corner of the Al –Si–Sm ternary system were determined by the examination of controlled heated and cooled specimens, as well as ...heat-treated specimens by means of optical and scanning electron microscopy, energy-dispersive X-ray spectroscopy, differential thermal analysis and X-ray diffraction. The Al-rich corner of the Al –Si–Sm ternary system comprises five regions of primary crystallisation (α
, β
, Al
Sm, Al
Si
Sm and AlSiSm) with following characteristic invariant reaction sequences: ternary eutectic reaction L → α
+ β
+ Al
Si
Sm, and two liquidus transition reactions, i. e., L + Al
Sm → α
+ AlSiSm, and L + AlSiSm → α
+ Al
Si
Sm. Along with the position of ternary eutectic and both interstitial points in the Al-rich corner of the Al-Si-Sm ternary system, the temperatures for each reaction were determined.
Improved sample wettability was obtained by oxygen plasma functionalization of pyrolytic graphite. The samples were exposed to highly dissociated oxygen plasma with the density of 1 x 10(16) m(-3), ...the electron temperature of about 5.5 eV and the density of neutral oxygen atoms of 8 x 10(21) m(-3) for 20 s. The surface wettability was measured by a contact angle of water drop. The contact angle dropped from original 112 down to about 1 deg .The functional groups were detected by XPS analyses. The survey spectrum showed a substantial increase of oxygen concentration on the surface, while high-resolution analyses showed additional oxygen was bonded onto the graphite surface in the form of C-O polar functional group responsible for the increase of the surface energy.
The quasicrystalline phase in melt-spun Al–Mn–Be alloys was investigated. In ribbons 40–60
μm thick the phase was present in the form of small particles rather uniformly dispersed in an aluminium ...solid solution matrix. The quasicrystalline phase had a primitive icosahedral structure. It was confirmed that it contained a substantial amount of Be. Nonetheless, it seemed that the electron-to-atom ratio remained close to that of binary Al
80Mn
20 quasicrystal.
Ledeburitic chromium steel X155CrVMo12.1 for cold-work tools was investigated in the quenched and tempered condition. Using appropriate investigative methods the evolution of the microstructure in ...all conditions was characterized. The change in state of a multicomponent matrix during tempering is crucial for attaining the required properties of this steel. In the material investigated, shape, size, fraction and distribution of eutectic (primary) carbides played a secondary role. The evolution of tempered martensite and precipitation of secondary hardening carbides of M
-type and MC-type from the supersaturated matrix during tempering led to secondary hardening and a secondary hardness peak at about 530 °C. The results show that steel X155CrVMo12.1 also exhibits performance ability at moderately elevated temperatures.
Magnetic micro-actuators and systems (MAGMAS) require tiny permanent magnets with dimensions of hundreds of micrometers. Such magnets need to have the highest possible energy density, which means ...Nd–Fe–B magnets are the most appropriate type. Most bottom-up fabrication techniques are either too slow or too expensive; top-down techniques involving machining tend to result in surface damage and a loss of magnetic properties. In this study, we have looked at very neodymium-rich Nd–Fe–B powders that allow us to sinter 100-μm-thick samples to full density at temperatures as low as 800
°C. These very thin magnets have coercivities of up to 1000
kA
m
−1 and are suitable for MAGMAS-type applications.
In a Late Bronze Age hoard at Kanalski Vrh in Slovenia, bronze pendants were found among numerous other artifacts. Among them a group of nine pendants of very similar compositions contained higher ...amounts of antimony, arsenic, nickel, cobalt, and iron, which suggested that speiss was added to bronze. Furthermore, most pendants had a silvery grey surface that differed from the common color of tin bronze, with about 13% Sn. One of the pendants was analysed by light optical and electron microscopy, Auger electron spectroscopy (AES), X-ray diffraction (XRD), and differential thermal analysis (DTA). Analyses revealed that the surface of the pendant was corroded, the copper alpha phase was eaten away, and the remaining eutectoid phase exhibited that silvery grey color. Comparison of chemical composition of the pendant and of compositions of speiss ingots found in the same hoard indicated that speisses could be used as alloying additions in making melts for casting pendants.
