scholarly journals Microstructure and Mechanical Strength of Attritor-Milled and Spark Plasma Sintered Mg-4Y-3Nd Alloy

Crystals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 574
Author(s):  
Mária Zemková ◽  
Peter Minárik ◽  
Michal Knapek ◽  
Stanislav Šašek ◽  
Jan Dittrich ◽  
...  
Keyword(s):  
Grain Size ◽  
Yield Strength ◽  
Mechanical Strength ◽  
Milled Powder ◽  
Secondary Phase ◽  
Size Refinement ◽  
Attritor Milling ◽  
Spark Plasma ◽  
Powder Particles ◽  
Microscopy Techniques

Gas-atomized powder of an Mg-4Y-3Nd magnesium alloy was attritor-milled at room temperature in an argon atmosphere for two time periods—1.5 and 5 h. Subsequently, the gas-atomized powder as well as both of the milled powders were spark plasma sintered at four temperatures, 400, 450, 500, and 550 °C, for 3 min. The effect of the milling on the powder particles’ morphology and the microstructure of the consolidated samples were studied by advanced microscopy techniques. The effect of the microstructural changes, resulting from the pre-milling and the sintering temperature, on the mechanical strength was investigated in compression along and perpendicular to the sintering load direction. Both the compression yield strength and ultimate compression strength were significantly affected by the grain size refinement, residual strain, secondary phase particles, and porosity. The results showed that attritor-milling imposed severe deformation to the powder particles, causing a significant grain size refinement in all of the consolidated samples. However, 1.5 h of milling was insufficient to achieve uniform refinement, and these samples also exhibited a distinctive anisotropy in the mechanical properties. Only a negligible anisotropy and superior yield strength were observed in the samples sintered from 5 h milled powder, whereas the ultimate strength was lower than that of the samples sintered from the gas-atomized powder.

scholarly journals Microstructure and texture in cryomilled and spark plasma sintered Ti Grade 2

2020 ◽  
Vol 321 ◽  
pp. 12030
Author(s):  
Jiří Kozlík ◽  
Josef Stráský ◽  
Petr Harcuba ◽  
Tomáš Chráska ◽  
Miloš Janeček
Keyword(s):  
Grain Size ◽  
Spark Plasma Sintering ◽  
Milled Powder ◽  
Recrystallization Process ◽  
Advanced Technique ◽  
Microstructural Investigation ◽  
Cryogenic Milling ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Powder Particles

Titanium (Grade 2) was processed by cryogenic milling and subsequently sintered by spark plasma sintering (SPS) method with the aim of creating and preserving the ultra-fine grained (UFG, < 1 μm) microstructure. Microstructural investigation was performed after both cryogenic milling and spark plasma sintering. An advanced technique of transmission Kikuchi diffraction (TKD) was used to characterize the individual milled powder particles. Investigations of milled powders showed significant grain refinement down to 50 nm after milling in liquid argon with tungsten carbide balls. We assume that this is the equilibrium grain size resulting from the balance of deformation, recovery and dynamic recrystallization. A texture, resembling the rolling texture in Ti, was also found in the milled particles, which can be explained by the nature of deformation during milling. UFG microstructure was not maintained after sintering, with the mean grain size of 2.6 μm. Although the grains are completely recrystallized, a texture, similar to the powder texture, was also found in these samples as a result of packing of the powder particles and the nature of the recrystallization process (continuous static recrystallization).

Evolution of phases during tempering of P91 steel at 760℃ for varying tempering time and their effect on microstructure and mechanical properties

2016 ◽  
Vol 231 (6) ◽  
pp. 1141-1161 ◽  
Author(s):  
C Pandey ◽  
MM Mahapatra
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Grain Size ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Yield Strength ◽  
Secondary Phase ◽  
Particle Spacing ◽  
Carbide Particles ◽  
Tempering Time

In the present investigation, a systematic study has been undertaken with regard to the effects of tempering time on room temperature mechanical properties of P91 (X10CrMoVNNB9-1) steel. Samples cut from P91 (X10CrMoVNNB9-1) industrial pipe were normalized at 1040 ℃ for 40 min and then tempered at 760 ℃ for different tempering times starting from 2 h to 8 h. Detailed analysis of microstructure, particle size, inter-particle spacing, and secondary phase carbide particles of the tempered samples was conducted by secondary electron microscopy technique. Optical microscopy was also utilized to characterize the tempered samples and for the measurement of grain size. In order to reveal the various phases formed during tempering of P91 (X10CrMoVNNB9-1) steel, X-ray diffraction was carried out . To study the fracture surface morphology of tensile tested and impact tested specimen field-emission scanning electron microscopy was carried out. The effect of tempering time on the microstructural parameters revealed an increase in grain size up to 4 h of tempering and then decreased because of recrystallization. The coarsening of secondary phase carbide particles M23C6 was revealed with an increase in tempering time. As a consequence, yield strength, hardness, and ultimate tensile strength were observed to decrease with increase in the tempering time. However, a drastic change was observed in the yield strength, ultimate tensile strength, and toughness after tempering for 6 h. From the present study, it was concluded that optimum combination of yield stress, ultimate tensile strength, hardness, and toughness obtained after tempering at 760 ℃ for 6 h.

The Strength and Ductility of 5483 Aluminium Alloy Processed by Various SPD Methods

2013 ◽  
Vol 765 ◽  
pp. 423-428 ◽  
Author(s):  
Piotr Bazarnik ◽  
Barbara Romelczyk ◽  
Mariusz Kulczyk ◽  
Małgorzata Lewandowska
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Mechanical Strength ◽  
Aluminium Alloy ◽  
Microstructural Analysis ◽  
Boundary Misorientation ◽  
Size Refinement ◽  
Specific Strength ◽  
Angular Pressing ◽  
Significant Difference

Grain size refinement is an efficient way to improve mechanical strength and thus make light metals even lighter in terms of specific strength. However, the strength improvement is at the expense of ductility. Therefore, a better understanding of microstructural factors influencing both parameters is of prime importance for further development of ultrafine grained materials. In this work, we report results obtained for 5483 aluminium alloy which was subjected to several severe plastic deformation (SPD) methods, i.e. equal channel angular pressing (ECAP), Hydrostatic Extrusion (HE) and the combination of the two. Detailed microstructural analysis revealed significant difference in the grain size and grain boundary characteristics between samples obtained following different routes. It was found that although the grain size is a prime microstructural parameter determining mechanical strength, second order factors such as grain size distribution and distribution of grain boundary misorientation angles also play a significant role.

scholarly journals Effect of Short Attritor-Milling of Magnesium Alloy Powder Prior to Spark Plasma Sintering

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 3973
Author(s):  
Peter Minárik ◽  
Mária Zemková ◽  
Michal Knapek ◽  
Stanislav Šašek ◽  
Jan Dittrich ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Magnesium Alloy ◽  
Spark Plasma Sintering ◽  
Alloy Powder ◽  
Mechanical Performance ◽  
Milled Powder ◽  
Plasma Sintering ◽  
Attritor Milling ◽  
Spark Plasma ◽  
Superior Mechanical Properties

The spark plasma sintering (SPS) technique was employed to prepare compacts from (i) gas-atomized and (ii) attritor-milled AE42 magnesium powder. Short attritor-milling was used mainly to disrupt the MgO shell covering the powder particles and, in turn, to enhance consolidation during sintering. Compacts prepared by SPS from the milled powder featured finer microstructures than compacts consolidated from gas-atomized powder (i.e., without milling), regardless of the sintering temperatures in the range of 400–550 °C. Furthermore, the grain growth associated with the increase in the sintering temperature in these samples was less pronounced than in the samples prepared from gas-atomized particles. Consequently, the mechanical properties were significantly enhanced in the material made of milled powder. Apart from grain refinement, the improvements in mechanical performance were attributed to the synergic effect of the irregular shape of the milled particles and better consolidation due to effectively disrupted MgO shells, thus suppressing the crack formation and propagation during loading. These results suggest that relatively short milling of magnesium alloy powder can be effectively used to achieve superior mechanical properties during consolidation by SPS even at relatively low temperatures.

scholarly journals Bimodal Microstructure in an AlZrTi Alloy Prepared by Mechanical Milling and Spark Plasma Sintering

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3756
Author(s):  
Orsolya Molnárová ◽  
Jan Duchoň ◽  
Esther de Prado ◽  
Štefan Csáki ◽  
Filip Průša ◽  
...  
Keyword(s):  
Spark Plasma Sintering ◽  
Mechanical Milling ◽  
Milled Powder ◽  
Sintered Sample ◽  
Second Phase ◽  
Bimodal Microstructure ◽  
Plasma Sintering ◽  
Second Phase Particles ◽  
Spark Plasma ◽  
Powder Particles

The aim of this study was to prepare a low porosity bulk sample with a fine-grained structure from an AlZrTi alloy. Nanostructured powder particles were prepared by mechanical milling of gas atomized powder. The mechanically milled powder was consolidated using spark plasma sintering technology at 475 °C for 6 min using a pressure of 100 MPa. Sintering led to a low porosity sintered sample with a bimodal microstructure. The sintered sample was revealed to be composed of non-recrystallized grains with an approximate size of about 100 nm encompassed by distinct clusters of coarser, micrometer-sized grains. Whereas the larger grains were found to be lean on second phase particles, a high density of second phase particles was found in the areas of fine grains. The microhardness of the milled powder particles was established to be 163 ± 15 HV0.01, which decreased to a slightly lower value of 137 ± 25 HV0.01 after sintering.

Mechanical properties of Mg-based materials fabricated by mechanical milling and spark plasma sintering

2018 ◽  
Vol 233 (10) ◽  
pp. 1972-1984 ◽  
Author(s):  
Mutlu Karasoglu ◽  
Serdar Karaoglu ◽  
Gursoy Arslan
Keyword(s):  
Grain Size ◽  
Yield Strength ◽  
Spark Plasma Sintering ◽  
Mechanical Milling ◽  
Microstructural Analysis ◽  
Compressive Yield Strength ◽  
X Ray ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Hardness Values

In this work, magnesium powders of different grain sizes were synthesized by mechanical milling for periods ranging from 0.5 to 30 h. Subsequent to milling, powders were consolidated by spark plasma sintering at 550 ℃ for 10 min. Before and after sintering, microstructural changes were investigated by analytical methods including X-ray diffraction (XRD), X-ray spectrometer, optical and electron microscopy. Analyses showed that nanocrystalline sizes were achieved by mechanical milling for milling times exceeding 5 h. Additionally, it was recognized that grain growth occurred during sintering, but to a limited extent. Mechanical test results displayed reasonable improvements in both compressive yield strength and hardness values with increasing milling times up to 5 h, where these reached their maximum values (245.5 MPa and 75.9 HV). The enhancement in these properties with increased milling time up to 5 h was attributed to both the extent of grain refinement and the formation of MgO together with incorporation of Fe particles, originating from the milling process, into the matrix. On the other hand, a substantial decrease in yield strength and hardness values in the samples milled in excess of 5 h were recorded, which in turn was related to the accompanying decline in bulk density of the samples. Microstructural analysis of the deformed samples revealed that grain size reduction suppressed twin formation, which elucidates the enhancement in ductility with decreasing grain size.

scholarly journals Mechanical Properties of Ti-15Mo Alloy Prepared by Cryogenic Milling and Spark Plasma Sintering

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1280 ◽  
Author(s):  
Anna Veverková ◽  
Jiří Kozlík ◽  
Kristína Bartha ◽  
Tomáš Chráska ◽  
Cinthia Antunes Corrêa ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Spark Plasma Sintering ◽  
Milled Powder ◽  
Two Phase ◽  
High Oxygen Content ◽  
Cryogenic Milling ◽  
Plasma Sintering ◽  
Refined Microstructure ◽  
Spark Plasma ◽  
Powder Particles

Metastable β-Ti alloy Ti-15Mo was prepared by cryogenic ball milling in a slurry of liquid argon. Material remained ductile even at low temperatures, which suppressed particle refinement, but promoted intensive plastic deformation of individual powder particles. Repetitive deformation of powder particles is similar to the multidirectional rolling and resembles bulk severe plastic deformation (SPD) methods. Initial and milled powders were compacted by spark plasma sintering. Sintered milled powder exhibited a refined microstructure with small β-grains and submicrometer sized α-phase precipitates. The microhardness and the yield tensile strength of the milled powder after sintering at 850 °C attained 350 HV and 1200 MPa, respectively. Low ductility of the material can be attributed to high oxygen content originating from the cryogenic milling. This pioneering work shows that cryogenic milling followed by spark plasma sintering is able to produce two-phase β-Ti alloys with refined microstructure and very high strength levels.

Synthesis of FeAl Hetero-Nanostructured Bulk Parts via Spark Plasma Sintering of Milled Powder

2006 ◽  
Vol 980 ◽  
Author(s):  
Thierry Grosdidier ◽  
Gang Ji ◽  
Frédéric Bernard ◽  
Sébastien Launois
Keyword(s):  
Grain Size ◽  
Spark Plasma Sintering ◽  
Sintering Temperature ◽  
Milled Powder ◽  
Large Temperature ◽  
Proper Selection ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Strength And Ductility ◽  
Selection Of

AbstractSpark plasma sintering (SPS) has been used in order to introduce nanocrystalline grains within fully dense FeAl consolidated parts. Hetero-nanostructured parts, consisting of nano, ultrafine and micrometric grains, have been successfully processed when milled - Y2O3 reinforced - FeAl powder was used. The large temperature differences that are spontaneously generated during the SPS process as well as the use of milled powder account for the formation of such interesting structures. The grain size distribution - that is suggested to be very potent to improve both strength and ductility - could be significantly modified by a proper selection of sintering temperature and holding time.

scholarly journals Microstructure and Mechanical Properties of Nanocrystalline Al-Zn-Mg-Cu Alloy Prepared by Mechanical Alloying and Spark Plasma Sintering

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1255 ◽  
Author(s):  
Cheng ◽  
Cai ◽  
Zhao ◽  
Yang ◽  
Chen ◽  
...  
Keyword(s):  
Grain Size ◽  
Ball Milling ◽  
Spark Plasma Sintering ◽  
Milling Time ◽  
Milled Powder ◽  
Bulk Alloy ◽  
Engineering Strain ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Ball Milling Time

In this study, Al, Zn, Mg and Cu elemental metal powders were chosen as the raw powders. The nanocrystalline Al-7Zn-2.5Mg-2.5Cu bulk alloy was prepared by mechanical alloying and spark plasma sintering. The effect of milling time on the morphology and crystal structure was investigated, as well as the microstructure and mechanical properties of the sintered samples. The results show that Zn, Mg and Cu alloy elements gradually dissolved in α-Al with the extension of ball milling time. The morphology of the ball-milled Al powder exhibited flaking, crushing and welding. When the ball milling time was 30 h, the powder particle size was 2–5 μm. The α-Al grain size was 23.2 nm. The lattice distortion was 0.156% causing by the solid solution of the metal atoms. The grain size of ball-milled powder grew during the spark plasma sintering process. The grain size of α-Al increased from 23.2 nm in the powder to 53.5 nm in the sintered sample during the sintering process after 30 h of ball milling. At the same time, the bulk alloy precipitated micron-sized Al2Cu and nano-sized MgZn2 in the α-Al crystal. With the extension of ball milling time, the compression strength, yield strength and Vickers hardness of spark plasma sintering (SPS) samples increased, while the engineering strain decreased. The compression strength, engineering strain and Vickers hardness of sintered samples prepared by 30 h milled powder were ~908 MPa, ~8.1% and ~235 HV, respectively. The high strength of the nanocrystalline Al-7Zn-2.5Mg-2.5Cu bulk alloy was attributed to fine-grained strengthening, dislocation strengthening and Orowan strengthening due to the precipitated second phase particles.

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