Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《材料研究学报》
Abstract： Pre-alloyed powders of T55 have been hot-isostatic-pressed (HIPed) at different HIPing temperatures, and the powder compacts were solution- and aging- treated. Thereafter the powder compacts were carefully examined to establish the relationship between their microstructure and mechanical property. Powder compacts HIPed at 940℃ and 970℃ showed no significant difference on the microstructure and tensile properties. Due to the densification wave effect caused by a non-uniformity of temperature/pressure field during HIPing, the recommended HIPing temperature is 940℃ in this work. The tensile property of powder compact at 600℃ was improved obviously after solution- and aging- treatment. The tensile property of the heat-treated powder compact is close to that of the wrought alloy but better than those of the cast ones. Finite element analysis was used to predict the final dimensions of the small casing component after HIPing, which is well consonant with the experimental data, thus, the FEM analysis is an efficient method for the design and manufacture of powder components. Based on the optimal container design and FEM analysis, a large thin-wall cylindrical structure of Ti55 alloys was manufactured successfully.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract： Pre-alloyed powders of Ti-47Al-2Cr-2Nb-0.15B (%, atom fraction) were prepared by an electrode induction melting gas atomization process, and powder metallurgy (PM) γ-TiAl alloys were prepared by hot isostatic press (HIP). Pre-alloyed powders of γ-TiAl were characterized. A comparison study was made between vacuum degassed and not degassed for the pre-alloyed powders and the PM alloys were subjected to tensile and rupture life test at different temperatures. Infrared spectrum analysis showed that the powders would absorb H2O when exposed in air. By getting rid of the absorbed H2O and O2 through a carefully designed vacuum degassing pre-treatment, the numbers of voids in the prepared PM γ-TiAl alloys decreased obviously, correspondingly the rupture life, as well as the consistency of room temperature tensile elongation, was also improved. In order to find out the influence of container materials on the microstructure and mechanical properties of the PM γ-TiAl alloys, two different container materials (CP-Ti and mild steel) were adopted. Experimental results showed that a lot of obvious voids appeared in the reaction zone due to severe reaction diffusion between the mild steel container and the PM γ-TiAl alloys when HIPed at 1260oC. The shielding effect of the mild steel container was stronger than that of the CP-Ti container, thus the densification shrinkage process of the CP-Ti canned PM γ-TiAl alloys would be more fully completed when HIPed at 1230oC compared with that of the mild steel canned PM γ-TiAl alloys, and thereby both of the yield and tensile strength were both improved. The γ-TiAl alloys prepared by powder metallurgy route present more uniform microstructure, finer grain and better properties compared with the casting alloys. Furthermore, the PM γ-TiAl alloys had no texture which was very common for the casting alloys.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract： Powder metallurgy (PM) Ti2AlNb alloy of Ti-22Al-24Nb-0.5Mo (atomic fraction, %) was prepared from pre-alloyed powder using hot isostatic pressing (HIPing). Compression tests of PM Ti2AlNb alloy, heat treated PM Ti2AlNb alloy and wrought Ti2AlNb alloy with the same chemical composition were conducted on Gleeble-3800 testing machine. The testing temperatures were from 930oC to 1050oC, strain rates varied from 0.001 s-1 to 10 s-1, and engineering strain was about 50% for each compression. The results show that the deformability of PM Ti2AlNb alloy is comparable to that of wrought alloy, and heat treatment has no obvious effect on the hot workability of PM Ti2AlNb alloy. The high temperature flow behavior of Ti2AlNb alloys prepared by different fabrication routes is similar in this work, while processing windows for PM Ti2AlNb alloy is broader than casting alloys especially at low temperature or relative high strain rate. PM Ti2AlNb billets for hot deformation were prepared by a typical powder metallurgy process, and were upset or drawn out to different deformation in two-phase region. Macrostructure of deformed PM Ti2AlNb billets were observed, no macro crack was found in deformed PM Ti2AlNb billets and the deformation was uniform. The results of tensile tests show that the deformed PM Ti2AlNb alloy after heat treatment presents better tensile properties.
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