The effects of up to 3 wt% Sn on the densification of Ti-6% Al-6%V alloys made by liquid phase sintering from premixed elemental powders or from prealloyed powders were investigated. Increases in Sn content and sintering temperature are both r e p o r t e d to e n h a n c e s i n t e r a b i l i t y . Homogenization heat treatment was used to develop uniform microstructures. HIP was reported to be required for the attainment of full density. Structures and mechanical properties are described.
microscopy. It is reported that Si and A1 are segregated at grain boundaries and other elements within the grains. The K bubble is used to explain creep behaviour.
DIAMOND AND GRAPHITE CRYSTALLIZATION UNDER CONDITIONS OF HIGH TEMPERATURE AND PRESSURE
Electrical and magnetic materials
USE OF PLASMA POWDER WELDING TO APPLY TITANIUM OVERLAY WITH DISPERSED TITANIUM CARBIDE
J.D. Park et al (Icheon University, Incheon, Korea), J Korean Inst of Metals, Vol 31, No 1, 1993, 39-47. (In Korean). Fe-16 at% Nd-5% B-1.5% Cu alloy magnets were prepared by hot pressing. A finite element method was used to calculate stress d i s t r i b u t i o n and showed t h a t compressive stress in the compressive direction was high in the centre of the specimen and declined towards the outside. It was reported that the highest values of magnetic properties were found at the midradius of the samples. This was attributed to process conditions.
L Varga et al (Budapest Technical University, Budapest, Hungary) Int J Refractory Metals & Hard Materials, Vol 11, No 5, 1992, 275-283. An investigation of the crystallization conditions for diamond and graphite in h i g h p r e s s u r e a n d t e m p e r a t u r e chambers is described. It is reported that the optimum conditions for yield of good quality crystals lie close to the d i a m o n d / g r a p h i t e e q u i l i b r i u m line. The proposed mechanisms are clustering and diffusion.
T. Tomita, Y. Hayashi (Inst of Industrial Research, Hyogo, Japan), J. Japan Inst of Metals, Vol 57, No 1, 1993, 68-74. (In Japanese). It is reported that a Ti-TiC alloy had been deposited on a Ti substrate by plasma spraying of powders. Effects of process conditions on the distribution of TiC in the matrix were determined. Composite TiTiC powders and mixed TiC and Ti powders were compared. The composite powder was found to give the more homogeneous deposit. LOOSE POWDER SINTERING OF POROUS TITANIUM PLATE Z. Jianbo et al (Non-Ferrous Metals Research Inst, Guangzhou, China), PM Technology, Vol 10, No 4, 1992, 282-286. (In Chinese). The use of loose powder sintering for the production of porous Ti plate is described. It is reported that the properties of the plate could be controlled by selection of powder particle size distribution and process conditions. The porous plates had been used for filtration of industrial effluent.
Tungsten OBSERVATION OF PARTICLE GROWTH DURING SINTERING OF TUNGSTEN IN NON-REDUCING ATMOSPHERES
EFFECTS OF STRESS ON CRYSTAL ORIENTATION AND MAGNETIC PROPERTIES OF HOT PRESSED NEODYMIUM-IRON-BORON MAGNETS
Hard materials and tool steels INFLUENCE OF COMPOSITION ON GAS PRESSURE SINTERED SILICON NITRIDE BASED MATERIALS J. Guoxin, W. Shenghong (Central Iron and Steel Research Inst, Beijing, China), PM Technology, Vol 10, No 4, 1992, 270-273. (In Chinese). It is reported that gas pressure sintering has been used, w i t h a d v a n t a g e , to consolidate SiaN4 alloys with additions of BN and MgO or SiO2. The additives are considered to en h an ce the sintering characteristics. Densification mechanisms are discussed. USE OF MAGNETIC PROPERTIES FOR NON-DESTRUCTIVE EVALUATION OF TUNGSTEN CARBIDE-COBALT
Z. Fang, J.W. Eason (Roger Tool Works Inc, Rogers, Arkansas, USA), Int J Powder Metallurgy, Vol 29, No 3, 1993, 259-265. The use of density and magnetic p r o p e r t i e s of WC-Co to e v a l u a t e c o m p o s i t i o n is r e p o r t e d . A d e n s i t y / magnetic saturation ((~sc) diagram is described which shows dependence of csc on C and Co contents and it is shown that C and Co contents can be determined from m e a s u r e m e n t s of d e n s i t y an d ~sc. Relationships between eoereiviW, WC grain size and Co and C contents are also BEHAVIOUR OF ALLOY ELEMENTS IN described. Grain size can be calculated SWAGED TUNGSTEN BILLET from an empirical relationship between X. Zhichang, Z. Ping (Tsinghua University, coercivity and mean free path of the Co Beijing, China), PM Technology, Vol 10, phase if the C and Co contents are known. The results are compared with No 4, 1992, 243-247. (In Chinese). experimental results using quantitative The distribution of doping elements in W wire was investigated by scanning electron metaUography.
I.H. Moon et al (Hanyang University, Seoul, Korea), Int J Refractory Metals & Hard Materials, Vol 11, No 5, 1992, 309-315. It is reported that W sinters at a lower rate in a non-reducing atmosphere and this was explained on the basis of particle growth. It is considered that mass transfer t h r o u g h t h e g a s e o u s p h a s e , by an o x i d a t i o n / r e d u c t i o n m e c h a n i s m , was responsible for particle growth.
STRENGTH AND THERMAL RESISTANCE OF SYNTHETIC DIAMONDS L. Varga et al (Budapest Technical University, Budapest, Hungary), Int J Refractory Metals & Hard Materials, Vol 11, No 5, 1992, 285-294. The structures of synthetic diamonds, f o r m e d by high p r e s s u r e processes, are discussed. The breaking strength and thermal resistance are considered to be the most important properties and it is sh o w n t h a t t h e s e ar e t e m p e r a t u r e d e p e n d e n t a n d a r e i n f l u e n c e d by conditions of synthesis. The properties are affected by the presence of impurities, inclusions and crystal habit. COMPOSITION MORPHOLOGY AND DISTRIBUTION OF RARE EARTHS IN CEMENTED CARBIDES L Chenguang (Research Inst, for NonFerrous Metals, Beijing, China), Int J Refractory Metals & Hard Materials, Vol 11, No 4, 1992, 295-302. The form and distribution of rare earth additions to WC-Co and WC-TiC-Co alloys were investigated. The findings are; uCo to ~Co change is found to be inhibited, there is solid solution strengthening of the binder and microstructural changes are described. COMPOSITION MORPHOLOGY AND DISTRIBUTION OF RARE ELEMENTS IN CEMENTED CARBIDES L. Chenguang (Research Inst for NonFerrous Metals, Beijing, China), Int J Refractory Metals & Hard Materials, Vol 11, No 5, 1992, 295-302. The form and distribution of rare earth additions to WC-Co and WC-TiC-Co a l l o y s w e r e i n v e s t i g a t e d by X-ray diffractometry and electron microscopy. It is r e p o r t e d t h a t the ¢¢Co to ~Co transformation is restricted, that there is solid solution strengthening of the matrix and that there are microstructural changes.
MPR March 1994 41