Microstructure and properties of hot isostatically pressed powder and extruded Ti25V15Cr2Al0·2C

Abstract

The influence of process route on the microstructure and tensile behaviour of specimens prepared from hot isostatically pressed powders and extruded ingot of the burn resistant alloy, Ti-25V-15Cr-2Al-0?2C (wt-%), has been investigated. Samples based on gas atomised (GA) and plasma rotating electrode process (PREP) powders have been studied. Microstructural examination shows that many PREP powder particles are single crystals, whereas GA particles are polycrystalline. The mechanical properties of hot isostatically pressed specimens have been assessed using tensile testing monitored by acoustic emission, while microstructures have been characterised by synchrotron X-ray microtomography and optical and analytical scanning electron microscopy. Tomographic examination revealed a small fraction (,0?002 vol.-%) of pores in samples made from hot isostatically pressed GA powders, but no porosity was detected in samples made from hot isostatically pressed PREP powder. In view of their similar tensile behaviour, it is concluded therefore that the porosity does not contribute to the scatter and poor ductility in these hot isostatically pressed samples. These pores increased in size and volume fraction after heat treatment above the hot isostatic press temperature. The large scatter in tensile properties of both hot isostatically pressed GA and PREP samples was correlated with the presence of large (100-400 mm) circular crack initiation sites on the fracture surfaces, but the origin of these initiation sites has not been identified.

Microstructure and Mechanical Properties of Powder Metallurgy Ti-22Al-24Nb-0.5Mo Alloys Joints with Electron Beam Welding

“…The low level of porosity could be readily visualized using the tomographic reconstruction technique. Synchrotron X-ray micro-tomography [16][17][18][19] was used to observe porosities in the PM Ti 2 AlNb compacts. The obtained data were post-processed using the commercial visualization and analysis software package Avizo.…”

The effect of cooling rates on the microstructure and mechanical properties of thermo-mechanically processed Ti–Al–Mo–V–Cr–Fe alloys

“…One of the most promising cost-effective powder metallurgical techniques is the blended elemental powder metallurgy (BEPM) method [7]. A number of Ti based alloys [7][8][9][10][11][12] have been produced using powder metallurgy technique where an additional processing step called hot isostatic pressing (HIP) is used in order to increase relative density or reduce the residual porosity. This results in an extra processing cost which compromises the cost savings of powder metallurgy technique.…”

Effect of Hot Isostatic Pressing and Heat Treatment on Microstructure and Mechanical Properties of Pm Ti‐22Al‐24Nb‐0.5Mo (At.%) Alloy

“…According to other researchers' study [6,10] , HIP'ing parameters (temperature, pressure and time), especially HIP'ing temperature has a significant effect on the porosity, microstructure and properties of PM alloys. In this study, four representative HIP'ing temperatures (930 o C, 980 o C, 1010 o C and 1030 o C) were selected based on DSC analysis.…”

“…Contaminations introduced during powder preparation, storage and processing reduced the performance of the PM alloys due to the early initiation of cracks at the sites of weak bonding between matrix and contamination-induced inclusions [6][7] . In this work, pre-alloyed powder of Ti-22Al-24Nb-0.5Mo (at.%) was prepared by gas atomization.…”

“…Micro-CT [6,9] was used to assess the porosity in PM Ti 2 AlNb alloys HIP'ed under different temperatures.…”