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Relationship of density to hardness of steam treated sintered iron
PM
P o w d e r Production P R O D U C T I O N OF A M O R P H O U S METAL POWDERS BY IMPACT FLATTENING O F D R O P L E T S ON ROTATING WHEEL
.~ Inoue, (Tohoku University, Sendai, Japan) J Japan Soc Powder and Powder Metallurgy, Vol 40, No 3, 1993, 347-354. (In Japanese). It is reported that amorphous Fe, Co and A1 alloy powders have been produced by impact flattening of atomized droplets on a rapidly spinning conical wheel. The particles were 1 to 3 ~m in thickness with an aspect ratio of 20 to 200. Structures were amorphous even in systems where no amorphous phase is formed by high pressure gas atomization. The formation o f amorphous structures is attributed to second stage cooling, reduction in powder thickness and rapid heat a b s t r a c t i o n on i m p a c t . T h e f l a k y pow de r s are shown to have s m o o t h surfaces, uniform thickness and high optical reflectivity, corrosion resistance, strength and anistropic magnetic properties. P R O D U C T I O N OF A M O R P H O U S METAL POWDERS BY IMPACT -- M E T H O D S FOR A D D I N G ALLOY E L E M E N T S IN POWDER METALLURGY P R O C E S S I N G
F. Molnar, J. Lezanski (Technical University, Kosice, Slovakia) Metal Proszkow, Vol 26, No 1-2, 1992, 31-35. (In Polish). A comparison and analyses are made of the m et h o d s used for addition of alloy elements in PM processing. Mixing of e l e m e n t a l p o w d e r s , p r e a l l o y i n g , e l e c t r o l y t i c an d e l e c t r o l e s s p l a t i n g , atomization of alloys and infiltration are considered.
Fundamentals CURVATURE OF I N T E R F A C E BOUNDARY B E T W E E N SOLID A N D LIQUID D U R I N G LIQUID PHASE SINTERING
M.M. Zivokovic (Belgrade University, Belgrade, Yugoslavia) Science o f Sintering, Vol 24, No 2, 1992, 133-138. A new method for the calculation of the curvature of the interface between solid and liquid in simulation of liquid phase sintering is described. The method is shown to be quick to use and to be s e n s i t i v e to grid l o c a t i o n if th e radius of curvature is less than the grid spacing.
48 MPR April 1994
LITERATURE
REVIEW
Sintering S I N T E R I N G M E C H A N I S M S IN T H E I N T E R M E D I A T E STAGE
W. Schatt, J.I. Boiko (University of Technology, Dresden, Germany) Science of Sintering, Vol 23, No 2, 1992, 95-103. The f u n d a m e n t a l s of f o r m a t i o n , interaction and relaxation of point, line, area and volume defects are explained. The role of lattice defects in densiflcation during the isothermal stage of sintering is shown.
PRODUCTS: Aluminium HIGH STRENGTH AND STIFFNESS ALUMINIUM-IRON-MANGANE SE ALLOYS MADE BY MECHANICAL ALLOYING
Y~P. Niu et al (Catholic University of Leuven, Heverlee, Belgium) Powder Metallurgy Int, Vol 25, No 3, 1993, 118-124. It is reported that A1-4wt%Mn-(3 to 6)%Fe alloys with high strength and stiflhess had been produced by mechanical alloying, heat treatment, second MA, degassing and extrusion. The preparation of composite powder with inert dispersoids and intermetallic dispersoids is described. The properties of the consolidated alloys at ambient and elevated temperatures are described.
Iron a n d s t e e l MICROSTRUCTURE A N D P R O P E R T I E S OF S I N T E R E D IRON
H. Danninger et al (Technical University, Vienna, Austria) Powder Metallurgy Int, Vol 25, No 3, 1993, 111-117. A novel approach to the study of microstructure/property relationships in sintered Fe is described. Microstructural p a r a m e t e r s are d i s c u s s e d and it is suggested that metallography may give incorrect information concerning m i c r o s t r u c t u r e , in p a r t i c u l a r p o r e connectivity. I m p o r t a n t concepts are reviewed and it is shown that they often start from ideas about structure which restricts the applicability in some cases. RELATIONSHIP OF DENSITY TO H A R D N E S S O F STEAM T R E A T E D S I N T E R E D IRON
G. Mair, (GKN Bound Brook, Bruneck, Italy)
Powder Metallurgy Int, Vol 25, No 3, 1993, 174-175. The hardness and local density of sintered and steam treated Fe cylinders was measured along the axis and the hardness/density relationship deduced. OPTIMIZATION OF T O U G H N E S S IN IMPACT F O R G E D 4 6 4 5 S T E E L S
D.W. Smith et al (Michigan Technological University, Houghton, USA) Int J Powder Metallurgy, Vol 29, No 4, 1993, 379-391. An investigation of the effects of deformation, microstructure and second phase particles on strength and toughness of powder forged 4645 steels, containing three levels of inclusion forming additives, is described. The structures were found to be similar to wrought steels with similar C contents. The PF steels showed greater tendency to undergo quasi-cleavage and it is deduced that the inclusions influence fracture toughness at similar strengths. Q u a n t i t a t i v e p r e d i c t i o n s of f r a c t u r e toughness were made using continuum and micromechanical methods to correlate inclusion effects and matrix ductility on void initiation and growth during ductile fracture. E F F E C T S OF OXYGEN C O N T E N T IN IRON POWDER ON PREPARATION O F IRON N I T R I D E S
If. Majima et al (Osaka University, Suito, Japan) J Japan Inst of Metals, Vol 57, No 2, 1993, 203-208. (In Japanese). It is reported that mechanical alloying in NH3 has been used to produce Fe16N2 powders from electrolytic and carbonyi Fe. The electrolytic Fe was found to nitride more quickly and suffer less oxidation than the carbonyl Fe. Increase in NHa was found to reduce the rate of oxidation. MA resulted in the formation of supersaturated solid solution below 14 to 15at%N and FeaN above 18 to 19%N. Mechanical grinding did not result in the formation of nitrides. STRUCTURAL EVOLUTION D U R I N G TRANSIENT LIQUID P H A S E S I N T E R I N G OF IRON-TITANIUM COMPACTS
A. Cias et al (Akademia Gorniczo-Hutnicxa, Krakow, Poland) Metal IVoszkow, Vol 26 No 1-2, 1993, 10-20. (In Polish). A study of structure evolution in Fe-Ti during liquid phase sintering of compacts made from elemental powder mixtures is described. Mechanisms of liquid phase formation are discussed. Swelling and
P o w d e r Production P R O D U C T I O N OF A M O R P H O U S METAL POWDERS BY IMPACT FLATTENING O F D R O P L E T S ON ROTATING WHEEL
.~ Inoue, (Tohoku University, Sendai, Japan) J Japan Soc Powder and Powder Metallurgy, Vol 40, No 3, 1993, 347-354. (In Japanese). It is reported that amorphous Fe, Co and A1 alloy powders have been produced by impact flattening of atomized droplets on a rapidly spinning conical wheel. The particles were 1 to 3 ~m in thickness with an aspect ratio of 20 to 200. Structures were amorphous even in systems where no amorphous phase is formed by high pressure gas atomization. The formation o f amorphous structures is attributed to second stage cooling, reduction in powder thickness and rapid heat a b s t r a c t i o n on i m p a c t . T h e f l a k y pow de r s are shown to have s m o o t h surfaces, uniform thickness and high optical reflectivity, corrosion resistance, strength and anistropic magnetic properties. P R O D U C T I O N OF A M O R P H O U S METAL POWDERS BY IMPACT -- M E T H O D S FOR A D D I N G ALLOY E L E M E N T S IN POWDER METALLURGY P R O C E S S I N G
F. Molnar, J. Lezanski (Technical University, Kosice, Slovakia) Metal Proszkow, Vol 26, No 1-2, 1992, 31-35. (In Polish). A comparison and analyses are made of the m et h o d s used for addition of alloy elements in PM processing. Mixing of e l e m e n t a l p o w d e r s , p r e a l l o y i n g , e l e c t r o l y t i c an d e l e c t r o l e s s p l a t i n g , atomization of alloys and infiltration are considered.
Fundamentals CURVATURE OF I N T E R F A C E BOUNDARY B E T W E E N SOLID A N D LIQUID D U R I N G LIQUID PHASE SINTERING
M.M. Zivokovic (Belgrade University, Belgrade, Yugoslavia) Science o f Sintering, Vol 24, No 2, 1992, 133-138. A new method for the calculation of the curvature of the interface between solid and liquid in simulation of liquid phase sintering is described. The method is shown to be quick to use and to be s e n s i t i v e to grid l o c a t i o n if th e radius of curvature is less than the grid spacing.
48 MPR April 1994
LITERATURE
REVIEW
Sintering S I N T E R I N G M E C H A N I S M S IN T H E I N T E R M E D I A T E STAGE
W. Schatt, J.I. Boiko (University of Technology, Dresden, Germany) Science of Sintering, Vol 23, No 2, 1992, 95-103. The f u n d a m e n t a l s of f o r m a t i o n , interaction and relaxation of point, line, area and volume defects are explained. The role of lattice defects in densiflcation during the isothermal stage of sintering is shown.
PRODUCTS: Aluminium HIGH STRENGTH AND STIFFNESS ALUMINIUM-IRON-MANGANE SE ALLOYS MADE BY MECHANICAL ALLOYING
Y~P. Niu et al (Catholic University of Leuven, Heverlee, Belgium) Powder Metallurgy Int, Vol 25, No 3, 1993, 118-124. It is reported that A1-4wt%Mn-(3 to 6)%Fe alloys with high strength and stiflhess had been produced by mechanical alloying, heat treatment, second MA, degassing and extrusion. The preparation of composite powder with inert dispersoids and intermetallic dispersoids is described. The properties of the consolidated alloys at ambient and elevated temperatures are described.
Iron a n d s t e e l MICROSTRUCTURE A N D P R O P E R T I E S OF S I N T E R E D IRON
H. Danninger et al (Technical University, Vienna, Austria) Powder Metallurgy Int, Vol 25, No 3, 1993, 111-117. A novel approach to the study of microstructure/property relationships in sintered Fe is described. Microstructural p a r a m e t e r s are d i s c u s s e d and it is suggested that metallography may give incorrect information concerning m i c r o s t r u c t u r e , in p a r t i c u l a r p o r e connectivity. I m p o r t a n t concepts are reviewed and it is shown that they often start from ideas about structure which restricts the applicability in some cases. RELATIONSHIP OF DENSITY TO H A R D N E S S O F STEAM T R E A T E D S I N T E R E D IRON
G. Mair, (GKN Bound Brook, Bruneck, Italy)
Powder Metallurgy Int, Vol 25, No 3, 1993, 174-175. The hardness and local density of sintered and steam treated Fe cylinders was measured along the axis and the hardness/density relationship deduced. OPTIMIZATION OF T O U G H N E S S IN IMPACT F O R G E D 4 6 4 5 S T E E L S
D.W. Smith et al (Michigan Technological University, Houghton, USA) Int J Powder Metallurgy, Vol 29, No 4, 1993, 379-391. An investigation of the effects of deformation, microstructure and second phase particles on strength and toughness of powder forged 4645 steels, containing three levels of inclusion forming additives, is described. The structures were found to be similar to wrought steels with similar C contents. The PF steels showed greater tendency to undergo quasi-cleavage and it is deduced that the inclusions influence fracture toughness at similar strengths. Q u a n t i t a t i v e p r e d i c t i o n s of f r a c t u r e toughness were made using continuum and micromechanical methods to correlate inclusion effects and matrix ductility on void initiation and growth during ductile fracture. E F F E C T S OF OXYGEN C O N T E N T IN IRON POWDER ON PREPARATION O F IRON N I T R I D E S
If. Majima et al (Osaka University, Suito, Japan) J Japan Inst of Metals, Vol 57, No 2, 1993, 203-208. (In Japanese). It is reported that mechanical alloying in NH3 has been used to produce Fe16N2 powders from electrolytic and carbonyi Fe. The electrolytic Fe was found to nitride more quickly and suffer less oxidation than the carbonyl Fe. Increase in NHa was found to reduce the rate of oxidation. MA resulted in the formation of supersaturated solid solution below 14 to 15at%N and FeaN above 18 to 19%N. Mechanical grinding did not result in the formation of nitrides. STRUCTURAL EVOLUTION D U R I N G TRANSIENT LIQUID P H A S E S I N T E R I N G OF IRON-TITANIUM COMPACTS
A. Cias et al (Akademia Gorniczo-Hutnicxa, Krakow, Poland) Metal IVoszkow, Vol 26 No 1-2, 1993, 10-20. (In Polish). A study of structure evolution in Fe-Ti during liquid phase sintering of compacts made from elemental powder mixtures is described. Mechanisms of liquid phase formation are discussed. Swelling and