Papers by Keyword: Powder Metallurgy (PM)

Abstract: A Ti-50at%Pt alloy synthesized using the spark plasma sintering (SPS) technique has been characterized for phases’ identification. TiPt alloys have potential use as high temperature shape memory alloys(HTSMAs). Test specimens were prepared at SPS temperature of 1300°C. Sintering pressure and time were varied. The microstructural features of the specimens were investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electron microscope used was equipped with an EDS detector, that, together with the XRD, were used for both the identification and analyses of the phases in the starting materials and the sintered alloys. High temperature XRD (800 -1300°C) as well as ambient temperature XRD analyses were done on the starting mechanically alloyed powders. All the samples tested at elevated temperatures were subsequently tested at room temperature after cooling. XRD analyses of the sintered samples were all done at room temperature. Analyses of the XRD results revealed new distinct phases from a temperature of 1000°C. A comparison of the room temperature XRD results for alloy powders and that of the sintered alloys was made. The following phases have been identified and studied TiPt B2, TiPt B19, Pt3Ti, Ti3Pt and Pt5Ti3. SPS pressure and sintering time did not show much effect on the phases detected. The alloy composition was found to be very inhomogeneous.

Abstract: Large-size Ni-based bulk metallic glass (BMG) composite samples exhibiting simultaneously high strength, enhanced plasticity and improved conductivity were produced by spark plasma sintering of mixed glassy powder blended with high-conductive Cu particulates. This opens new possibilities for the applications of the BMG composites as functional and structural materials.

Abstract: Cu–Co–based alloys are the new generation of metal matrix for diamonds by powder metallurgy processed cutting tools. These alloys are created with the purpose of reducing the cobalt content in diamond tools. Cu-Co-based alloys matrix were fabricated using a hot pressing process at the temperature of 710°C , 750°С and 790°С by 15 MPa. Structures formed during sintering were studied by XRD and WDS. Micro-structural aspects were observed by EPMA. Densification, hardness, yield strength and compressive yield strength were performed. The results showed as follows: Cu-Co-based alloy matrix is composed by gray pre-alloyed particles, Cu-Sn binary solid solution, copper-rich phase and interface between particles and matrix; The higher sintering temperature, the more dendrite phase, in addition, the diffusion of carbon occurs; the holding force from matrix to particles becomes larger and the distribution of particles becomes more uniform; As the sintering temperature increased, the mechanical properties of Cu-Co-based alloy matrix enhanced.

Abstract: Fe-1.5Cu-1.5Ni-0.5Mo-0.3C alloy was prepared by powder metallurgy (P/M) warm compaction. Under the conditions of compaction pressures of 600 or 800 MPa and compaction temperature of 100 or 120°C , sintered in cracked ammonia atmosphere at 1120°C for half an hour, the researched alloy samples with higher properties could be prepared. The results show: when formed at a compaction pressure of 800 MPa and compaction temperature of 120°C , the alloy presented a sintered density 7.41g/cm³, hardness 88HRB, ultimate tensile strength 593MPa， yield strength 585MPa, and elongation 3.8%. Their mechanical properties, crack morphology and surface composition weres analyzed.

Abstract: The paper deals with the influence of severe plastic deformation on the typical powder metallurgy (PM) microstructural characteristics, such as porosity, of a PM aluminum alloy. A commercial ready-to-press aluminum based powder was used as material to be investigated. After applying different compacting pressures (400, 500, 600 and 700 MPa), specimens were debinded in a ventilated furnace at 400 °C for 60 min. Sintering was carried out in a vacuum furnace at 610 °C for 30 min. The specimens were ECAPed for 1 pass. The dimensional and morphological porosity of investigated materials were measured individually for each pore. Results show that ECAP generates shearing stress breaking down the oxide film; this, coupled to particles deformation under local constraints, enables strong bonding and stability. Therefore, ECAP supports next progressive decreasing of pore size as well as strongly influences both dimensional and morphological porosity characteristics, considering that small pores evolve easily to a circular form. Moreover, ECAP cause strong bonding between adjacent particles, which results in a significant increase of mechanical properties.

Abstract: The possibilities of Cu-Al2O3 particulate reinforced composites, of competitive functional properties, processing by the classical powder metallurgy route have been investigated taking into consideration its known technical and economical advantages in respect to the known worldwide investigated technological routes of their processing. The adopted compositions, of (5.0÷20.0) [vol.%] Al2O3, were selected in agreement with published data for a large range of applications. Pharmaceutical homogenization method applied for powder mixtures preparation proved to assure a high homogeneity, evidenced by SEM and EDS analyses. Their determined compressibility has shown that, for all compositions, the obtainable compactness is very close to that of pure Cu (even over 94 %). Cold uniaxial compaction at 500 and 700 MPa, and subsequent sintering in argon of high purity at 800 °C for 45 and 60 min have been adopted for composites realization. The performed analysis of the compacting pressure and sintering time influence on the composite compactness proved that, beside the above specified values obtaining for 700 MPa and 60 minute processing parameters, high enough values, acceptable for numerous applications, can be also obtained at 500 MPa and 60 or even 45 minutes. Finally, microstructural analysis highlighted that, by the adopted processing conditions, a high uniformity of Al2O3 particles distribution in the Cu matrix can been assured, both creating premises for obtaining good functional properties of Cu-Al2O3 composites, proving the competitiveness of the investigated PM route for their elaboration.

Abstract: MMCs components are mostly produced using near net shape manufacturing methods and are subsequently machined to the final dimensions and surface finishes. The MMCs consist of extremely hard reinforcing particles and pose considerable challenges due to the poor machinability and severe wear of the cutting tool. In this study, cutting performance of WC, CBN and PCD cutting tools were investigated with respect to surface roughness during machining of 10 wt % SiCp reinforced Al-Si alloy matrix composites produced by powder metallurgy (PM) method. Average surface roughness (Ra) corresponding to each machining condition was measured. After the machining process the worn insert tips were examined under the scanning electron microscope (SEM). Chip geometry and machined surface photographs have been taken by optical microscopy. The experimental results showed that surface roughness decreased with increasing cutting speed for all of cutting tool materials. The best surface integrity was occurred after the machining with PCD insert at the highest cutting speed employed.

Abstract: In this study the formation of the liquid phase during sintering process of Fe-Cu-Sn-Pb system was investigated. In order to reach this purpose a new material based on iron powder was developed using PM technologies. Additions like copper, tin and lead were added to iron powder and the mixture was sintered in dry hydrogen atmosphere at different temperatures and maintaining time. The liquid phase formed during sintering led to a considerable accurate process and swelling of the sintered compact was observed and studied.

Abstract: In this study, electrolyze unit, which is used for the production of metal powders, was designed and produced. The production of powder was carried out by using different parameter times of powder removal (5, 10, 20, 30 and 40 min.). The effect of time of powder removal on powder particle size and shape was examined. Laser particle measurement machine and SEM were also used to measure particle size and particle shape respectively. Experimental results indicated that an increase in time of powder removal caused an increase in powder particle size and its shape changed from acicular dentritic to globular dentritic.

Abstract: In this study, the machinability of the Cu matrix composites reinforced with 5, 10, 15 and 20 vol.% of Al2O3 particulates produced by powder metallurgy have been investigated. The effects of compaction pressure, sintering duration and volume fraction of reinforcing component on the surface roughness during machining of the considered composites, obtained by the appropriate Cu-Al2O3 powder mixtures cool die pressing at 500, respectively 700 MPa, and sintered at 800 °C for durations of 45 and 60 minutes in an argon atmosphere were determined. The machining tests were performed on a CNC machining centre, by means of samples face milling in dry conditions, at two different feed rates and four different cutting speeds, while the depth of cut was kept constant. As cutting tools have been adopted commercial grade (H13A) uncoated cemented carbide inserts manufactured by Sandvik Coromant with the geometry of TPKN1603 PP-R. After the machining tests, the surface roughness measurements clearly showed an increasing trend in surface roughness when the feed rate is increased from 300 mm/min to 400 mm/min for both sintering durations. Surface damages created on the machined surface through release from the matrix of particles negatively impact surface roughness. The most stable results in terms of surface roughness were obtained at 20% reinforcing ratio for 700 MPa compacting pressure and 60 minutes sintering duration.