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Microstructure of rapidly solidified titanium aluminide powders
forging. A power law relationship between d e n s i t y and a p a r a m e t e r , ~, w h i c h is defined as the ratio of horizontal and v e r t i c a l c o n s t r a i n t s , is e s t a b l i s h e d . Structures and properties were investigated and it is reported t h a t the properties of the sinter-forged materials are s u p e r i o r to t h o s e of c o n v e n t i o n a l l y produced alloys. The shearing action of the process is said to have a beneficial effect on densification. DIE D E S I G N FOR HOT FORGING OF SINTERED IRON PREFORMS K.S. Panday (Regional Engineering College, Tiruchipalli, India), Powder Metallurgy Science and Technology, Vol 4, No 1, 1992, 35-46. The p a p e r describes an investigation of die design for hot forging of sintered Fe powder preforms. The dies are designed to a c c o m m o d a t e situations where there is a change of c o m p o n e n t s h a p e and well as densification. Based on the results of plane upsetting tests using open and closed dies, dies of various shapes were designed for use on friction screw presses. The production of structurally sound and mechanically strong parts is reported. STRUCTURAL EVOLUTION OF IRON-MANGANESE ALLOYS DURING EXTRUSION T.F. Volynova et al, Poroshkovaya Metallurgiya, No 5, 1992, 29-37. (In Russian). It is shown from a study of structural transformation in Fe-Mn alloys, produced from atomized powder, that the processes of static and dynamic recrystallization do n o t p r o c e e d to c o m p l e t i o n . T h i s is attributable to the failure of nuclei to grow. E F F E C T S OF TIME AND TEMPERATURE OF SINTERING ON PHYSICO-MECHANICAL PROPERTIES OF A STEEL A.I. Uliyanov et al, Poroshkovaya Metallurgiya, No 5, 1992, 38-43. (In Russian). The effects of variations in sintering time and t e m p e r a t u r e on the mechanical and m a g n e t i c p r o p e r t i e s of a s t e e l w e r e investigated with the objective of establishing relationships between strength, magnetic saturation and coercivity. The q u a l i t y of s i n t e r i n g is shown to be related to a change in elastic modulus. SURFACE ALLOYING OF PM IRON BASE ALLOYS S.G. Agbalyan et al, Poroshkovaya Metal lurgiya, No 5, 1992, 53-59. (In Russian). The formation of Fe-C-Cr, Fe-C-Cr-Ni and Fe-C-Cr-Mo powder layers on steel substrate was studied. Phases identified included (~ + Cr + (Fe,Mo) 7C:0.
E F F E C T S OF POROSITY OF POWDER S T E E L S ON STRENGTH U N D E R VISCOUS FAILURE
e n h a n c e s the mechanical properties. It is considered t h a t a complex oxide of K, A1 and Si contributed to bubble formation.
S.A. Firstov et al, Poroshkovaya Metallurgiya, No 5, 1992, 95-98. (In Russian).
GRAIN BOUNDARY S E G R E G A T I O N IN MOLYBDENUM ALLOYS AND E F F E C T ON INTERGRANULAR FRACTURE
An investigation of the influence of p o r o s i t y on t h e b r e a k i n g s t r e s s of consolidated powder Fe is described. It is n o t e d t h a t in general t h e s t r e n g t h is d e p e n d e n t on structural conditions prior to failure in p a r t i c u l a r t h e dislocation structure which d e t e r m i n e s d e f o r m a t i o n characteristics. A model, based on physical details is p r o p o s e d which allows correlation between strength and porosity. WEAR RESISTANT S I N T E R E D MATERIALS FROM 'FERRO-TITANIT' WASTE SHAVINGS A.Cias a n d T. Pieczonka ( A c a d e m y of Mining and Metallrugy, Carcow, Poland),
Powder Metallurgy Science and Technology, Vol 4, No 1, 1992, 47-54. The use of a powder, m a d e from waste shavings of Fe-33 wt% TIC-3% Cr-3% Mo1.5% Cu by mechanical comminution, to p r o d u c e c o m p o n e n t s is described. The materials are r e p o r t e d to have controlled porosity, density and physical properties. The wear properties were assessed on pino n - r i n g t e s t s u n d e r dry o r p a r t i a l l y lubricated conditions and are shown to be better t h a n the steels compared.
Titanium MICROSTRUCTURE OF RAPIDLY SOLIDIFIED TITANIUM ALUMINIDE POWDERS M.Cao et al (Academia Sinica, Shenyang, China), Acta Metallurgica Sinica, Vol 28, No 10, 1992, A428-A430. (In Chinese). The characteristics of Rs Ti-34 wt% A1-2% Mn gas atomized powders are described. The mean particle size is 27 ~m and t h e structure is shown to consist of a major (~2 p h a s e and a minor 7 phase. There were equixed and dendritic grains. After annealing the powder the ~ t r a n s f o r m e d into equilibrium 7 p h a s e with a refinement of the microstructure.
Molybdenum RECRYSTALLIZATION AND DOPANT BEHAVIOUR OF MOLYBDENUM WIRE J-D. Kim et al (Korean Tungsten Co., Daegu, Korea), J Korean Inst of Metals, Vol 30, No 11, 1992, 1308-1316. (In Korean). The effects of doping on the mechanical properties of Mo wire were investigated with respect to heat treatment t e m p e r a t u r e . Recrystalliszation a n d t h e formation of bubbles were detected. It is r e p o r t e d t h a t the bubbles in the d o p e d wire
A.V. Krajnikov et al (Ukraine Academy of Sciences, Kiev, Ukraine), Int J Refractory Metals & Hard Materials, Vol 11, No 3, 1992, 175-180. It is noted t h a t e m b r i t t l e m e n t in group 6A refractory metals is often associated with interstitial impurities and precipitation of grain boundary phases. An investigation of e m b r i t t l e m e n t of Mo is d e s c r i b e d . It is r e p o r t e d t h a t t h e t e m p e r a t u r e d e p e n d e n c e of segregation of O and C in recrystallized Mo is non-linear and results from structural changes, dislocation substructure disintegration, grain growth and grain boundary migration. A c o r r e l a t i o n is e s t a b l i s h e d b e t w e e n grain b o u n d a r y c h e m i s t r y and cold brittleness.
Nickel MICROSTRUCTURE OF AN OXIDE DISPERSION STRENGTHENED MECHANICALLY ALLOYED NICKEL BASE ALLOY POWDER W.()sterle a n d X.P. Li. (BAM, Berlin, G e r m a n y ) , Z fitr Metallkunde, Vol 84, No 2, 1993, 85-90. (In German). The role of MA in the production of oxide dispersion s t r e n g t h e n e d (ODS) Ni base alloys is discussed and it is noted t h a t microstruetural evolution is w e l l d o c u m e n t e d for the consolidation stage b u t n o t for t h e MA stage. A f t e r MA electron microscopy showed that the s t r u c t u r e c o n s i s t e d of Ni-Cr-Al s o l i d solution with particles of refractory metals the grain size being a b o u t 50 nm. After milling the Y203 could not be detected but a p p e a r e d only after h e a t t r e a t m e n t at 1000°C.
Tungsten A S P E C T S OF RESEARCH AND DEVELOPMENT ON T U N G S T E N AND T U N G S T E N ALLOYS W.D Schubert (Technical University, Vienna, Austria), Int J Refractory Metals & Hard Materials, Vol 11, No 3, 1992, 151-157. Aspects of research into W and its alloys is discussed with reference to the current m a r k e t s i t u a t i o n for W a n d t r e n d s in materials science, the possible impact of R&D on the e n d - u s e r is discussed with regard to p a t t e r n s of W consumption. A range of applications and the recycling of W are considered.
MPR July\August 1993 45
E F F E C T S OF POROSITY OF POWDER S T E E L S ON STRENGTH U N D E R VISCOUS FAILURE
e n h a n c e s the mechanical properties. It is considered t h a t a complex oxide of K, A1 and Si contributed to bubble formation.
S.A. Firstov et al, Poroshkovaya Metallurgiya, No 5, 1992, 95-98. (In Russian).
GRAIN BOUNDARY S E G R E G A T I O N IN MOLYBDENUM ALLOYS AND E F F E C T ON INTERGRANULAR FRACTURE
An investigation of the influence of p o r o s i t y on t h e b r e a k i n g s t r e s s of consolidated powder Fe is described. It is n o t e d t h a t in general t h e s t r e n g t h is d e p e n d e n t on structural conditions prior to failure in p a r t i c u l a r t h e dislocation structure which d e t e r m i n e s d e f o r m a t i o n characteristics. A model, based on physical details is p r o p o s e d which allows correlation between strength and porosity. WEAR RESISTANT S I N T E R E D MATERIALS FROM 'FERRO-TITANIT' WASTE SHAVINGS A.Cias a n d T. Pieczonka ( A c a d e m y of Mining and Metallrugy, Carcow, Poland),
Powder Metallurgy Science and Technology, Vol 4, No 1, 1992, 47-54. The use of a powder, m a d e from waste shavings of Fe-33 wt% TIC-3% Cr-3% Mo1.5% Cu by mechanical comminution, to p r o d u c e c o m p o n e n t s is described. The materials are r e p o r t e d to have controlled porosity, density and physical properties. The wear properties were assessed on pino n - r i n g t e s t s u n d e r dry o r p a r t i a l l y lubricated conditions and are shown to be better t h a n the steels compared.
Titanium MICROSTRUCTURE OF RAPIDLY SOLIDIFIED TITANIUM ALUMINIDE POWDERS M.Cao et al (Academia Sinica, Shenyang, China), Acta Metallurgica Sinica, Vol 28, No 10, 1992, A428-A430. (In Chinese). The characteristics of Rs Ti-34 wt% A1-2% Mn gas atomized powders are described. The mean particle size is 27 ~m and t h e structure is shown to consist of a major (~2 p h a s e and a minor 7 phase. There were equixed and dendritic grains. After annealing the powder the ~ t r a n s f o r m e d into equilibrium 7 p h a s e with a refinement of the microstructure.
Molybdenum RECRYSTALLIZATION AND DOPANT BEHAVIOUR OF MOLYBDENUM WIRE J-D. Kim et al (Korean Tungsten Co., Daegu, Korea), J Korean Inst of Metals, Vol 30, No 11, 1992, 1308-1316. (In Korean). The effects of doping on the mechanical properties of Mo wire were investigated with respect to heat treatment t e m p e r a t u r e . Recrystalliszation a n d t h e formation of bubbles were detected. It is r e p o r t e d t h a t the bubbles in the d o p e d wire
A.V. Krajnikov et al (Ukraine Academy of Sciences, Kiev, Ukraine), Int J Refractory Metals & Hard Materials, Vol 11, No 3, 1992, 175-180. It is noted t h a t e m b r i t t l e m e n t in group 6A refractory metals is often associated with interstitial impurities and precipitation of grain boundary phases. An investigation of e m b r i t t l e m e n t of Mo is d e s c r i b e d . It is r e p o r t e d t h a t t h e t e m p e r a t u r e d e p e n d e n c e of segregation of O and C in recrystallized Mo is non-linear and results from structural changes, dislocation substructure disintegration, grain growth and grain boundary migration. A c o r r e l a t i o n is e s t a b l i s h e d b e t w e e n grain b o u n d a r y c h e m i s t r y and cold brittleness.
Nickel MICROSTRUCTURE OF AN OXIDE DISPERSION STRENGTHENED MECHANICALLY ALLOYED NICKEL BASE ALLOY POWDER W.()sterle a n d X.P. Li. (BAM, Berlin, G e r m a n y ) , Z fitr Metallkunde, Vol 84, No 2, 1993, 85-90. (In German). The role of MA in the production of oxide dispersion s t r e n g t h e n e d (ODS) Ni base alloys is discussed and it is noted t h a t microstruetural evolution is w e l l d o c u m e n t e d for the consolidation stage b u t n o t for t h e MA stage. A f t e r MA electron microscopy showed that the s t r u c t u r e c o n s i s t e d of Ni-Cr-Al s o l i d solution with particles of refractory metals the grain size being a b o u t 50 nm. After milling the Y203 could not be detected but a p p e a r e d only after h e a t t r e a t m e n t at 1000°C.
Tungsten A S P E C T S OF RESEARCH AND DEVELOPMENT ON T U N G S T E N AND T U N G S T E N ALLOYS W.D Schubert (Technical University, Vienna, Austria), Int J Refractory Metals & Hard Materials, Vol 11, No 3, 1992, 151-157. Aspects of research into W and its alloys is discussed with reference to the current m a r k e t s i t u a t i o n for W a n d t r e n d s in materials science, the possible impact of R&D on the e n d - u s e r is discussed with regard to p a t t e r n s of W consumption. A range of applications and the recycling of W are considered.
MPR July\August 1993 45