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Processing TiAl-Based Alloy by Elemental Powder Metallurgy
Yong LIU,Baiyun HUANG,Yuehui HE,Kecheo ZHOU,

材料科学技术学报 , 2000,
Abstract: TiAl-based alloys with various compositions (includingTi-48Al, Ti-47Al-2Cr-2Nb, Ti-47Al-2Cr-2Nb-0.2B and Ti-47Al-3Cr, in mole fraction) had been prepared by elemental powder metallurgy (EPM). The results have shown that the density of the prepared Ti-48Al alloy increases with increasing hot pressing temperature up to 1300 degreesC. The Ti-48Al alloy microstructure mainly consisted of island-like Ti3Al phase and TiAl matrix at hot pressing temperature below 1300 degreesC, however, coarse alpha (2)/gamma lamellar colonies and gamma grains appeared at 1400 degreesC. It has also indicated that the additions of elemental Cr and B can refine the alloy microstructure. The main microstructural inhomogeneity in EPM TiAl-based alloys was the island-like aa phase or the aggregate of alpha (2)/gamma lamear colony, and such island-like structure will be inherited during subsequent heat treatment in (alpha+gamma) field. Only after heat treatment in a field would this structure be eliminated. The mechanical properties of EPM TiAl-based alloys with various compositions were tested, and the effect of alloy elements on the mechanical properties was closely related to that of alloy elements on the alloy microstructures. Based on the above results, TiAl-based alloy exhaust valves were fabricated by elemental powder metallurgy and diffusion joining. The automobile engine test had demonstrated that the performance of the manufactured valves was very promising for engine service.
Properties of duplex stainless steels made by powder metallurgy  [PDF]
L.A. Dobrzański,Z. Brytan,M. Actis Grande,M. Rosso
Archives of Materials Science and Engineering , 2007,
Abstract: Purpose: of this paper was to examine the mechanical properties of duplex stainless steels.Design/methodology/approach: In presented study duplex stainless steels were obtained through powder metallurgy starting from austenitic, martensitic base powders by controlled addition of alloying elements, such as Cr, Ni, Mo and Cu. In the studies behind the preparation of mixes, Schaeffler’s diagram was taken into consideration. Prepared mixes have been sintered in a vacuum furnace with argon backfilling at 1260°C for 1 h. After sintering: rapid cooling have been applied in argon atmosphere. Produced duplex stainless steels have been studied by scanning and optical microscopy. Mechanical properties such as tensile strength, impact energy, hardness and wear rate were evaluated.Findings: According to achieved results, it was affirmed that applied sintering method as well as powder mixes preparation allows for manufacturing the sintered duplex steels with good mechanical properties which depends on austenite/ferrite ratio in the microstructure and elements partitioning between phases. The additions of alloying elements powders (promoting formation ferritic and austenitic phase) to master alloy powder, makes possible the formation of structure and properties of sintered duplex stainless steels. Sintered duplex steels obtained starting from austenitic and ferritic powders with admixture of elemental powders achieve lower mechanical properties when compared to composition obtained by mixing ferritic and austenitic powder in equal amounts.Research limitations/implications: According to the powders characteristic, the applied fast cooling rate seems to be a good compromise for mechanical properties and microstructures, nevertheless further tests should be carried out in order to examine different cooling rates.Originality/value: The use of elemental powders added to a stainless steel base showed its potentialities, in terms of fair compressibility and final sintered density. In addition a good microstructural homogeneity and first of all mechanical properties and corrosion resistance was achieved, also working with cycles possible for industries.
Production of a low young modulus titanium alloy by powder metallurgy
Santos, Dalcy Roberto dos;Henriques, Vinicius André Rodrigues;Cairo, Carlos Alberto Alves;Pereira, Marcelo dos Santos;
Materials Research , 2005, DOI: 10.1590/S1516-14392005000400014
Abstract: titanium alloys have several advantages over ferrous and non-ferrous metallic materials, such as high strengthto-weight ratio and excellent corrosion resistance. a blended elemental titanium powder metallurgy process has been developed to offer low cost commercial products. the process employs hydride-dehydride (hdh) powders as raw material. in this work, results of the ti-35nb alloy sintering are presented. this alloy due to its lower modulus of elasticity and high biocompatibility is a promising candidate for aerospace and medical use. samples were produced by mixing of initial metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by isochronal sintering between 900 up to 1600 °c, in vacuum. sintering behavior was studied by means of microscopy and density. sintered samples were characterized for phase composition, microstructure and microhardness by x-ray diffraction, scanning electron microscopy and vickers indentation, respectively. samples sintered at high temperatures display a fine plate-like a structure and intergranular b. a few remaining pores are still found and density above 90% for specimens sintered in temperatures over 1500 °c is reached.
Workability Behaviour of Powder Metallurgy Aluminium Composites  [PDF]
S. Narayan,A. Rajeshkannan
Journal of Powder Technology , 2014, DOI: 10.1155/2014/368721
Abstract: An efficient way to find the workability limit for powder metallurgy parts has been suggested. Compacts of Al-4%TiC, Al-4%WC, Al-4%Fe3C, and Al-4%Mo2C were produced to the relative density of 0.82 and 0.86 with three different geometries through primary operations of powder metallurgy routes. Each sintered compact was hot deformed to various strain levels till a visible crack appeared at the free surface. Oyane’s fracture principle was used to develop a theory to study powder metallurgy compacts. A least square technique was used to determine the constants in fracture criteria and these equations were finally used to find workability limit. It is found that the projected technique was well in agreement with the experimental values. 1. Introduction Powder metallurgy manufacturing technique is used to produce parts to close tolerance, intricate shapes, and near net shapes. It has proved to be cost effective of producing many parts such as porous materials, composite materials, refractory materials, and special high duty alloys [1–3] to be used in aircraft, automotive, and manufacturing industry. Further, powder metallurgy route is green manufacturing and energy efficient manufacturing compared to casting operation [4]. Aluminum metal matrix is used for wide range of industrial applications due to its exceptional properties such as low specific density, great strength, low thermal growth, and decent wear resistance and is cost-effective [5–9]. Ductile aluminum matrix strengthened with tougher and stiffer carbides offers a blend of properties of the metallic material and ceramic strengthening parts [10]. Titanium carbide and tungsten carbide based parts are presently used in high strength application where better strength, wear resistance, and corrosion resistance are necessary [11, 12] and aluminium reinforced with tungsten carbide prepared by warm accumulative roll bonding method exhibited enhanced mechanical properties [13]. The workability of the powder metallurgy parts plays an important part in defining if the powder metallurgy part will be shaped successfully or fracture initiates in the forming practice. Workability is the amount of deformation in which a material can sustain the induced internal stresses of forming prior to failure. Workability features are dependent not only on the material but also on numerous forming parameters such as stress and strain rate, porosity, friction, and temperature [14, 15]. Over the years, numerous models [16–18] were established to study workability of conventional parts; however, they cannot be directly applied
SYNTHESIS OF TiAl+TiB_2 COMPOSITE AND-ITS THERMAL STABILITY
QU Xuanhui HUANC Baiyun LEI Changming CHEN Shiqi Central South University of Technology,Changsha,China professor,Powder Metallurgy Research Institute,Central South University of Technology,Changsha,China,
QU Xuanhui HUANC Baiyun LEI Changming CHEN Shiqi Central South University of Technology
,Changsha,China professor,Powder Metallurgy Research Institute,Central South University of Technology,Changsha,China

金属学报(英文版) , 1993,
Abstract: Synthesis process of a TiAl+TiB_2 composite from the elemental powders was studiedby means of differential scanning calorimetry and X-ray diffractometry.TiB_2 particlesmay form in TiAl matrix at temperature even below 700℃ owing to the exothermicreactions between Ti and Al powders.TiB_2 particles are very thermally stable,and theyalmost did not change in their relative amount,morphology and size after the synthesizedcomposite was remelted.In addition,the existence of TiB_2 particles has obvious refiningeffect in the as-cast microstructure of TiAl-base alloys.
New alloying systems for ferrous powder metallurgy precision parts  [PDF]
Danninger H.,Gierl C.
Science of Sintering , 2008, DOI: 10.2298/sos0801033d
Abstract: Traditionally, the common alloy elements for sintered steels have been Cu and Ni. With increasing requirements towards mechanical properties, and also as a consequence of soaring prices especially for these two metals, other alloy elements have also become more and more attractive for sintered steels, which make the steels however more tricky to process through PM. Here, the chances and risks of using in particular Cr and Mn alloy steels are discussed, considering the different alloying techniques viable in powder metallurgy, and it is shown that there are specific requirements in particular for sintering process. The critical importance of chemical reactions between the metal and the atmosphere is described, and it is shown that not only O2 and H2O but also H2 and even N2 can critically affect sintering and microstructural homogenization.
Production of titanium alloys for advanced aerospace systems by powder metallurgy
Henriques, Vinicius André Rodrigues;Campos, Pedro Paulo de;Cairo, Carlos Alberto Alves;Bressiani, José Carlos;
Materials Research , 2005, DOI: 10.1590/S1516-14392005000400015
Abstract: titanium alloys parts are ideally suited for advanced aerospace systems because of their unique combination of high specific strength at both room temperature and moderately elevated temperature, in addition to excellent corrosion resistance. despite these features, use of titanium alloys in engines and airframes is limited by cost. the alloys processing by powder metallurgy eases the obtainment of parts with complex geometry. in this work, results of the ti-6al-4v and ti-13nb-13zr alloys production are presented. samples were produced by mixing of initial metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering between 900 up to 1500 °c, in vacuum. sintered samples were characterized for phase composition, microstructure and microhardness by x-ray diffraction, scanning electron microscopy and vickers indentation, respectively. it was shown that the samples were sintered to high densities and presented homogeneous microstructure from the elements dissolution with low interstitial pick-up.
Improvement of Ductility of Powder Metallurgy Titanium Alloys by Addition of Rare Earth Element
Yong LIU,Lifang CHEN,Weifeng WEI,Huiping TANG,Bin LIU,Baiyun HUANG,
Yong
,LIU,Lifang,CHEN,Weifeng,WEI,Huiping,TANG,Bin,LIU,Baiyun,HUANG

材料科学技术学报 , 2006,
Abstract: Ti-4.5Al-6.0Mo-1.5Fe, Ti-6Al-1Mo-1Fe and Ti-6Al-4V alloys were prepared by blended elemental powder metallurgy (PM) process, and the effects of Nd on the microstructures and mechanical properties were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD).It was found out that the addition of Nd increased the density of sintered titanium alloys slightly by a maximum increment of 1% because small amount of liquid phase occurred during sintering. The addition of Nd shows little effect on the improvement of tensile strength, while the elongation is significantly improved. For example, the elongation of Ti-4.5Al-6.0Mo-1.5Fe can be increased from 1% without addition of Nd to 13% at a Nd content of 1.2 wt pct.
Properties of rhenium-based master alloys prepared by powder metallurgy techniques  [PDF]
A. Wrona,M. Staszewski,M. Czepelak,M. Woch
Archives of Materials Science and Engineering , 2010,
Abstract: Purpose: The aim of this work was to investigate an effect of phase composition, microstructure and selected properties of the rhenium-based alloys on the conditions of their preparation by mechanical alloying followed by pressure sintering.Design/methodology/approach: The structure and mechanical and physical properties of the Re-14.0% Ni, Re-13.7% Co and Re-9.1% Fe alloys prepared from pure metal powders by mechanical alloying in a planetary mill for 10 hours followed by sintering conducted for 1 hour at the temperature of 1150°C under the pressure of 600 MPa were investigated.Findings: The mechanical alloying results in partial dissolving of alloy components into each other, whereas their structure remains unchanged, and in a decrease in average density of powders and average diameter of their particles. As a result of sintering the alloy additives almost fully pass into rhenium-based solid solution. Density and hardness of the sinter compacts and homogeneity of alloying elements distribution were higher at longer times of mechanical alloying.Research limitations/implications: The obtained results provide complementary information on the possibility of obtaining high-melting alloys by mechanical alloying and on the rate of structural transformations taking place as a result of this process.Practical implications: The obtained materials can be used as master alloys for the production of contact materials and superalloys, providing higher homogeneity of the chemical composition and microstructure of the final products.Originality/value: A new method for preparation of rhenium-based alloys by means of mechanical alloying and powder metallurgy techniques has been successfully tested.
MICROSTRUCTURE OF RAPIDLY SOLIDIFIED TiAl ALLOY POWDER
CAO Mingzhou HAN Dong ZHANG Tao LI Dong Institute of Metal Research,Academia Sinica,Shenyang,China Associate Professor,
CAO Mingzhou HAN Dong ZHANG Tao LI Dong Institute of Metal Research
,Academia Sinica,Shenyang,China Associate Professor,Institute of Metal Research,Academia Sinica,Shenyang,China

金属学报(英文版) , 1993,
Abstract: The rapidly solidified powder of Ti-34Al-2Mn alloy was obtained by means of ultrasonicgas atomisation (USGA) technique.The tupical size of the powder is 27 μm.X-ray diffractionresults show that the powder consists of major α_2-phase and minor γ-phase.Under opticalmicroscope both equiaxed and dendritical microstructure features were observed on RS pow-der sections.After annealing at 900 ℃/for 2 h in vacuum,most of α_2-phase transforms intoγ-phase,resulting in refinement of structure.
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