processed. Fe-lO%Zr-20%B powders, in which Ni replaced some of the Fe, was mechanically alloyed. The Ni was reported to accelerate amorphisation and to enhance thermal stabili- ty of the amorphous powder. Recrystallisation kinetics were shown to vary with Ni content. Ni contents of 7 to 28% were studied.

Improvement of thermoelectric properties of bismuth telluride by mechanical alloying

S.Turenne et af (EC& Polytechnique, Canada.)

Production of Bi telluride materials by PM methods, mechanical alloying, pressing, sinter- ing, hot extrusion and heat treatment, from elemental Bi, Ti and Se powders, was outlined. Evolution of microstructure throughout pro- cessing was described. Extrusion was shown to be particularly important to development of the crystallographic texture needed to obtain thermoelectric properties comparable with sin- gle crystal materials made by the Bridgeman method.

Powder injection moulding Gel strengthening additives for agar based binder for injection moulding feedstock

J.L&& et al. (Polymer Technologies Inc., USA.)

It was reported that a gel forming agaroid polysaccharide and a gel forming solvent had been used in formulation of an injection moulding binder. The strength of the gel was shown to be important in facilitating removal of the moulded part from the die and reducing cycle time. Effects of gel strengthening addi- tives were investigated and were found to increase the gel strength by 37%.

Recyclability of injection moulding feedstock

J.B.Kolts, K.M.Kulkami. (Advanced Metalworking

Practices Inc., USA.)

It was noted that in injection moulding much of the feedstock remains as runner scrap and only a small proportion is in the part. The scrap must be recycled but there is little data about the effects of recycling. An investigation in which process waste was recycled up to 13 times, with tests of feedstock properties and part characteristics after each, was described. The feedstock studied was reported to have good ability to be recycled without need for intermediate processing.

Optimised injection moulding with aqueous gel binders

J.ESteuenson et ai. (Honeywell lntemationai, Inc.,

USA.)

It was shown that use of aqueous gel binders allows large moulds to be filled at low temperatures and pressures and that

40 MPR May 2002

process conditions can readily be optimized. Experimental and simulated studies were carries out to identify the most favourable process conditions for minimum part vari- ability. The simulation used a code incorpo- rating thermal contact resistance at the mould surface.

Effect powder particle size and alloying technique on distortion in injection moulded parts

D.T.Whychell. (CM Furnaces Inc., USA.)

Distortion in injection moulded parts was

discussed and the lack of a standard test was noted. Distortion arises from a variety of

sources. A study of the effects of feedstocks containing 316L and 17-4PH stainless steel powders on distortion was described. Nine feedstocks were prepared from prealloyed steel powders or carbonyl Fe with 1.5X gas atomized master alloy powders. Sag of flat test bars, dur- ing thermal treatment, was monitored. Test data were presented and discussed.

Cemented carbides Toughcoated hard powders for hardmetals with novel properties

P.Ettmuyer et al. (Technological University, Vienna,

Austria.)

Limitations to mechanical properties of materials were reviewed. Tough-coated pow- ders were described as hard refractory particles with a coating of WC-Co which, when consol, idated formed, a cellular structure of intercon, netted tough shells with hard wear resistant cores. In use the wear resistant surface is con- tinuously renewed. An example, TiN coated with WC-Co, was given. Formation of car- bonitrides is avoided. Production, characteris- tics and comparison with conventional tool materials were described.

Double-cemented carbide composite

P.Pattersm et al. (Unwersity of Alabama, USA.)

Double-cemented carbide materials were

described. These consist of granules of WC-Co in a metal matrix, Co or steel. This was shown to improve wear resistance and toughness com- pared with conventional WCCo. Production by hot pressing of granules of different sizes was described. The steel matrix materials were heat-treated. Effects of process and material parameters on structure and properties were described.

Engineered composite powders

A.J.Shennm, D.Baker. (Powdmnet Inc., USA.)

Characteristics of a range of composite car-

bide materials were described with reference to variations in microstructure, production and performance. Materials are produced using a wide range of processes. Grain coarsening and

particle rearrangement during sintering were discussed.

Sinter hardening Optimisation of furnace atmosphere for sinter hardening

C.Blais et al. (Do&r Metal Powders Ltd., Canada.)

Sinter hardening of steel parts was reviewed with regard to material and process character- istics, in particular cooling rate from sintering temperature. It was noted that little attention had been given to effects of furnace atmos- phere composition on sinter hardening. Experiments and calculations to optimise the use of H in the cooling zone of sintering fur- naces were carried out and the results present- ed and compared.

Influence of sinter furnace cycle on parameters of sinter hardened parts

O.Mars et al. (North American Htigmiis, USA.)

Effects of cooling rate on the structure of steel were discussed in relation to sinter hard- ening. Relationship between sintering furnace cycle characteristics, heating rate, time, tem- perature, furnace atmosphere and cooling rate and structure were investigated for a range of cycles. Structures and process cycle character- istics were correlated

Intermetallic materials Sintering of titanium carbide-nickel base intermetallic composites

A. Woods et al. (Southern Ilhnois University, USA.)

NiCr and NiFeCr intermetallic compounds, with 50 to 7Ovol%TiC, were processed con- ventionally by ball milling and batch sintering or, unconventionally, by turbomilling and

continuous sintering. Process conditions were

described. Full density was attained by both methods. Structures and properties of both types of material were compared. It was report- ed that unconventional processing gave advan-

tages in costs and structure/property relation- ships.

Thermo-mechanical properties of titanium-nickel shape memory alloys

H.Kyogoku et al. (Kinki University, Jopan.)

TiNi shape memory alloys were fabricated

by spark plasma sintering from elemental

powders. Process conditions were investigated

with regard to thermo-mechanical properties

of the sintered materials. Highest density

attained was 96.6% at 880°C. Thermo-

mechanical properties were enhanced by heat

treatment. Properties were discussed. Tensile

strength of 400MPa, with 5.5% elongation,

was attained for solution treated Ti- 5l.Oat%Ni alloys.

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