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Wpływ szybkości nagrzewania na zmiany wymiarowe towarzyszące spiekaniu reakcyjnemu układów Fe-Al i Fe-Al-Si

Pieczonka T., Kazior J., Gialanella S., Molinari A., Skrzypek S. J.

Rudy i Metale Nieżelazne

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2000

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R. 45, nr 4

272-276

PL

Proces spiekania reakcyjnego układów Fe-Al i Fe-Al-Si kontrolowano za pomocą dylatometru. Spiekaniu poddawano wypraski wykonane z proszków elementarnych. Celem badań było określenie wpływu szybkości nagrzewania, ciśnienia prasowania oraz obecności krzemu na zmiany wymiarowe spiekanych kształtek. Analiza dylatometryczna umożliwiła również określenie mechanizmów mających znaczenie podczas spiekania reakcyjnego badanych układów. Z uwagi na to, że faza ciekła pojawia się w spiekanych układach tuż przed reakcją syntezy faz międzymetalicznych i jeszcze przed osiągnięciem temperatury spiekania izotermicznego całkowicie zanika, głównym efektem dylatometrycznym jest pęcznienie kształtek. Wzrost szybkości nagrzewania ogranicza rozmiary tego pęcznienia.

EN

Reactive sintering process of Fe-Al and Fe-Al-Si systems was controlled by dilatometry. Green compacts were made using elemental powders mixtures. The influence of heating rate, pressing pressure and silicon addition on dimensional changes occuring during sintering was established. Some mechanisms taking place during that process were recognized and discussed. Since the liquid phase appears in investigated systems just before the self-propagating high temperature synthesis (SHS) reaction starts and even below the isothermal sintering temperature is reached, swelling is the main dillatometric effect of the sintering. Higher heating rate reduces the scale of the swelling.

2

Thermal fatigue resistance of the salt quenched AISI H11 hot work tool steel.

Molinari A., Gialanella S., Straffelini G.

Inżynieria Materiałowa

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1998

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R. XIX, nr 3

372-379

EN

In the present work the thermal fatigue resistance of a typical hot work tool steel was studied. The material was subjected to salt quenching, by cooling the specimens in two different ways. The first cooling cycle produces a coarser microstructure than the second one, and induces the formation of upper bainite. While the thermal fatigue crack density is the same in the two materials, a clear difference in their propagation was found. The coarser microstructure and the presence of upper bainite tend to reduce the thermal fatigue resistance.

3

Effect of heating rate on the synthesis of nickel aluminides by reactive sintering.

Gialanella S., Pieczonka T., Molinari A., Kazior J.

Inżynieria Materiałowa

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1998

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R. XIX, nr 4

909-912

EN

Dimensional changes occuring during reactive sintering of three different elemental nickel - aluminium powder mixtures were investigated. Sintering process of powder compacts was curried out under vacuum in a horizontal dilatometer at a various heating rates. The synthesis reaction proceeded with a sudden release of heat and sudden dimensional changes, corresponding to the appearance of liquid phase in the system. Heating rate is a crucial parameter affecting the dominant sintering mechanisms: both extensive shrinkage as well as extensive swelling were observed for each investigated mixture composition depending on the actual heating rate. At slower heating rate the synthesis reactions were initiated and developed between solid powders of nickel and aluminium. In these cases, owing to the limited amount of liquid phase which developed, a swelling of compacts was observed. However, at the higher heating rate solid state reactions were limited and after transient swelling also shrinkage was observed.