Reactive spray processing of advanced materials

Spray forming alloying REACTIVE ADVANCED

- reactive

SPRAY PROCESSING MATERIALS

Electrical materials OF

A.Lawley et al. (Drexel University, USA.) Material synthesis by reactive processing was discussed with regard to structure, properties and uses of spray forming in Osprey and plasma modes. Phase regimes of interest are gas/liquid, liquid/solid, liquid/ liquid and if there is subsequent thermal processing, solid/solid. Fundamental issues in reactive spray processing, energetics, fluid flow, diffusion and phase transformation were critically considered. The current status of the technology was reviewed with regard to materials formulation and possible future developments were indicated. COPPER REACTIVE

BASE COMPOSITES SPRAY DEPOSITION

BY

D.Morris, A.Benghalem (University of Neuchatel, Neuchatel, Switzerland.) The need for Cu alloys with high strength and electrical conductivity was discussed using Cu with AlaOs, synthesized by internal oxidation of the Al, as an example. There are some production problems with this alloy. Spray forming was considered to make this material but has different difficulties. It was noted that a cast alloy of Cu with Fe, Cr or Nb yields a strength of 1008 MPa and 80% conductivity after heavy deformation. The use of rapid solidification techniques followed by heavy deformation was reported to give compposite structures with a grain size below 50 nm with fibres less than 4nm thick. Results were discussed with respect to structure/property relationships and the behaviour of matrix and fibre during deformation. SOLIDIFICATION AND MICROSTRUCTURESOFSPRAY FORMED HIGH SPEED

STEELS

S.Eon et al. (Research Inst. of Industrial Science and Technology, Pohang, Korea.) Structural evolution in spray formed HSS was investigated with emphasis on eutectic carbide morphology. Atomized powders were shown to contain fine dendrites and a continuous carbide network. Spray cast alloys showed finely dispersed MC and a discontinuous MzC carbide network. Droplets in flight partially solidified and fragmented on impact, remelted and solidified rapidly forming M& carbides which decomposed into MC and M& on annealingIt was considered that the enthalpy of the droplets was the major factor controlling final microstructure.

36

MPR November

1996

and

STRUCTURE SINTERING

magnetic

FORMATION OF OXIDE

DURING MAGNETS

G.Yaglo (Don State University, Rostov-on Don, Russia.) An investigation of fabrication of Ba-Sr magnets by pressing in a magnetic field and sintering was described. Grain size in the magnet was an order of magnitude different than in the powder. The magnet was shown to have a comb-like structure. This was considered to increase strength and to prevent internal shrinkage. SOFT MAGNETIC MATERIALS TRANSFORMERS SINTERED IRON BASED POWDERS

FOR FROM

V.Vasilyev, M.V.Lulko (Don State University, Rostov-on Don, Russia.) Soft magnetic materials, made by PM, were discussed with regard to processing and properties. It was reported that reduction annealing of the powders reduced powder loss in service. Optimum composition and process comnditions were outlined. Fe powders coated with P were shown to yield magnets with good properties. TESTING TUNGSTEN

OF PROPERTIES HEAVY ALLOYS

OF

J.Bucki et al. (University of Technology, Warsaw, Poland.) Experiments to ascertain if magnetic properties of W heavy alloys can be used to assess quality were described. It was reported that the alloys had very weak, if properties. This was any, magnetic attributed to the W content of the matrix and intermetallic phases. INVESTIGATIONS OF PRECIPITATED PHASES IN LIQUID PHASE SINTERED TUNGSTEN ALLOYS

G.L.Zu (Central Iron and Steel Research Inst., Beijing, China.) The microstructure of W-C-Cu-MgO-Ni alloys was examined. The precipitated phase made up 75% of the structure which was identified as a complex cubic carbide approximating to (W,C),Cu. Studies of mechanical properties suggested that this is responsible for the strength and ductility of the alloy.

Intermetallic STATISTICAL INTERMETALLIC POWDERS

A statistical study of the influence of powder characteristics on consolidation and sintering of Fe based intermetallic materials was described. This was reported to have established criteria for the dispersivity of the powders and lead to improved quality. MECHANICAL ALLOYING WAVE CONSOLIDATION ALUMINIDES

AND SHOCK OF TITANIUM

G.Frommeyer et al. (Max-Planck Inst., Dusseldorf, Germany.) Investigations of mechanical alloying, to give nano-crystalline and amorphous powders, and shock wave compaction, as a method of preparing Ti aluminides, were described. Microstructural evolution, phase formation and thermal stability of the powder were determined. Explosives with detonation velocities of 2000 to 8000 m.sec-’ were used to study the effect of consolidation conditions on structure and properties. FORMATION OF IRON-TITANIUM CARBIDE CERMET BY REACTION FERRO-TITANIUM AND CARBON

OF

V.Potapenko, M.S.Kovaltchenko. (Ukraine Academy of Sciences, Kiev, Ukraine.) Physico-chemical processes occuring during heating of mixtures of fen-o-Ti and C were investigated. An exothermic reaction was initiated by heating to 1085°C forming a cermet containing 75%TiC which was further densified by hot pressing. The process was rapid and resulted in a fine grained structure.

Powder production and propagating high temperature synthesis MECHANICAL NANOSIZED BORIDES

ALLOYING TITANIUM

OF CARBIDES

se/f

AND

I.I.Timofeev et al. (Inst. for Problems of Materials Science, Kiev, Ukraine.) Mechanochemical methods of initiating solid state reactions were discussed. Studies of synthesis of important carbides and borides were described. Studies of mechanical alloying, by planetary ball milling, of Ti-C and Ti-B-C, leading to amorphization of the powders, were described. Results of powder characterization were used to monitor the MA.

materials ANALYSIS IRON

AGGLOMERATION OF ATOMIZED POWDERS

OF BASED

Y.F.Sapelkina (Don State Technical sity, Rostov-on-Don, Russia.)

Univer-

SPHERICAL

GAS

C.Aslund (Scandanavian Powdertech, Sweden.) Development of a novel process for agglomeration of spherical gas atomized