A New Dental Superalloy System: IV. X-Ray Diffraction Analysis

X-ray diffraction analysis of the alloy system Co-Ni-Cr-Ta showed that the ternary alloy base consisted of three phases (a, β, and σ). Addition of Ta caused a decrease in the intensity of the β lines. Further Ta additions caused diffraction lines characteristic of the intermetallic compound α-Co3Ta. At higher Ta concentrations, the intensity of the lines characteristic of the σ phase increased and lines characteristic of Co2Ta appeared.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66588/2/10.1177_00220345730520041701.pd

FERRITE GRAIN REFINEMENT IN SEAMLESS PIPES THROUGH INTRAGRANULAR NUCLEATION ON VN

Mill rolling process of seamless pipe was simulated with the aim of applying grain refinement through theformation of intragranular ferrite on VN precipitated inside austenitic grains, for production of as-hot rolledmicrostructures, which are currently attained only by in-line normalising. Tests were performed on V+N andV+N(Ti) steels using two types of schedules with long and short transfer/heating times prior to sizing between930-830°C. It was found that transfer/heating time between high temperature rolling and low temperaturesizing could be used for precipitation of VN in austenite which in turn can nucleate intragranular ferritegrains on cooling. To facilitate the precipitation process of VN a sub-micro-addition of Ti was used which alsohelps to restrain austenite grain growth during piercing and pipe forming. Subsequent V(C,N) precipitationof the remaining vanadium in the ferrite contributes precipitation strengthening. Hot rolling followed byintragranular ferrite formation in 0.1%V-0.015%N-0.005%Ti steel is able to develop a fine ferrite-pearlitemicrostructure with an average ferrite grain size of 7um

Dispersion strengthening in vanadium microalloyed steels processed by simulated thin slab casting and direct charging. Part 2 - chemical characterisation of dispersion strengthening precipitates

The composition of the sub-15 nm particles in six related vanadium high strength low alloy steels, made by simulated thin slab direct charged casting, has been determined using electron energy loss spectroscopy (EELS). Such particles are considered to be responsible for dispersion hardening. For the first time, particles down to 4 nm in size have had their composition fully determined. In all the steels, the particles were nitrogen and vanadium rich and possibly slightly sub-stoichiometric carbonitrides. Equilibrium thermodynamics predicted much higher carbon to metal atomic ratios than observed in all cases so that kinetics and mechanical deformation clearly control the precipitation process. Thus it is important to formulate the steel with this in mind

Effect of Tantalum Additions to a Cobalt-Chromium-Nickel Base Alloy

An investigation by electron diffraction, transmission and scanning electron microscopy, and energy-dispersive X-ray analysis has shown that Ta additions to a 40-30-30 Co-Cr-Ni-base alloy strengthen by ordering and by formation of coherent α-Co3Ta precipitate. However, increasing Ta content increases the proportion of the hexagonal phase and decreases ductility.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67626/2/10.1177_00220345740530022401.pd