Microstructural evolution of Y2O3 and MgAl2O4 ODS EUROFER steels during their elaboration by mechanical milling and hot isostatic pressing

2004 ◽  
Vol 335 (1) ◽  
pp. 83-102 ◽  
Author(s):  
C. Cayron ◽  
E. Rath ◽  
I. Chu ◽  
S. Launois
Keyword(s):  
Microstructural Evolution ◽  
Mechanical Milling ◽  
Hot Isostatic Pressing ◽  
Isostatic Pressing

Microstructural Changes of a Creep-Damaged Nickel-Based K002 Superalloy Containing Hf Element under Different HIP Temperatures

2016 ◽  
Vol 35 (2) ◽  
pp. 153-159 ◽  
Author(s):  
Xiaomeng Wang ◽  
Yu Zhou ◽  
Jian Dong ◽  
Tianyou Wang ◽  
Zihua Zhao ◽  
...  
Keyword(s):  
Microstructural Evolution ◽  
Temperature Increase ◽  
Volume Fraction ◽  
Hot Isostatic Pressing ◽  
Nucleation And Growth ◽  
Dissolution Process ◽  
Microstructural Changes ◽  
Isostatic Pressing ◽  
Solute Atoms

AbstractEffects of hot isostatic pressing (HIP) temperature on the microstructural evolution of a nickel-based K002 superalloy containing Hf element after long-term service were investigated using three different soaking temperatures during HIP. The degraded γ′ precipitates represented coarse and irregular morphology after long-term service. These γ′ precipitates still were of coarse and irregular shape, but the size and volume fraction of γ′ precipitates were markedly reduced under HIP condition of 1,190°C/200 MPa/4 h, indicating that the γ′ precipitates were experiencing a dissolution process. Meanwhile, the concentrically oriented N-type γ′ rafting structure around the cavities was formed. With HIP temperature increase to 1,220°C and 1,250°C, the small-sized, cubic and regular γ′ precipitates were re-precipitated, and the concentrically oriented γ′ structure vanished. The unstable morphology induced by the nucleation and growth of γ matrix was found near the creep cavities, indicating that the solute atoms diffused inward the creep-induced cavities during HIP. However, at HIP temperature of 1,220°C and 1,250°C, a large number of blocky MC(2)-type carbides containing amounts of Hf elements were precipitated, demonstrating that HIP treatment at higher temperatures can result in the formation of a large number of blocky MC(2)-type carbides.

Mechanical Properties and Fracture Behaviour of Nanostructured and Ultrafine Structured TiAl Alloys Synthesised by Mechanical Milling of Powders and Hot Isostatic Pressing

2011 ◽  
Vol 683 ◽  
pp. 149-160 ◽  
Author(s):  
De Liang Zhang ◽  
Hong Bao Yu ◽  
Yuong Chen
Keyword(s):  
Mechanical Milling ◽  
Room Temperature ◽  
Hot Isostatic Pressing ◽  
High Energy ◽  
Grain Boundary Sliding ◽  
High Oxygen Content ◽  
Tial Alloys ◽  
Isostatic Pressing ◽  
Grain Sizes ◽  
Boundary Sliding

Bulk nanostructured (grain sizes in the range of 50-200nm) and ultrafine structured (grain sizes in the range of 100-500nm) -TiAl based alloys with compositions Ti-47Al (in at%) and Ti–45Al–2Cr–2Nb–1B–0.5Ta (in at%), respectively, have been produced using a combination of high energy mechanical milling of mixtures of elemental powders and hot isostatic pressing at 800 and 1000oC respectively, and the microstructures of the samples have been characterised. At room temperature, the HIPed samples fractured prematurely at tensile stresses in the range of 200-300MPa and showed no ductility, very likely due to the relative high oxygen content (0.6wt%) in the samples and very low tolerance of TiAl based alloys on dissolved oxygen. At 800oC, the HIPed samples showed a yield strength in the range of 55-70MPa, a tensile strength in the range of 60-80MPa, a large amount of elongation to fracturing around 100% and clear strain softening. Examination of the fractured tensile test specimens at room temperature and 800oC showed that the level of the consolidation was fairly high, but the HIPed samples do contain a small fraction of interparticle boundaries with weak atomic bonding. The fracture of the HIPed samples in tensile testing at room temperature and 800oC, respectively, is predominately intergranular, and the large amount of plastic deformation prior to fracture at 800oC is achieved mainly through grain boundary sliding in conjunction with dislocation gliding, in agreement with the deformation mechanisms of nanostructured and ultrafine structured alloys generally agreed by researchers.

Ultrafine Grained Ti-47Al-2Cr (at%) Alloy Prepared by High Energy Mechanical Milling and Hot Isostatic Pressing

2007 ◽  
Vol 29-30 ◽  
pp. 139-142 ◽  
Author(s):  
Vijay Nadakuduru ◽  
Peng Cao ◽  
De Liang Zhang ◽  
Brian Gabbitas
Keyword(s):  
Mechanical Milling ◽  
Composite Powder ◽  
Hot Isostatic Pressing ◽  
High Energy ◽  
Layered Composite ◽  
Hot Workability ◽  
Major Barrier ◽  
Isostatic Pressing ◽  
Specific Strength ◽  
Ultrafine Grained

Gamma TiAl based alloys are important materials with potential applications in aerospace and automotive applications due to their high specific strength and creep resistance. The major barrier for their applications is their limited ductility at room temperature and limited hot workability. One way of overcoming this barrier is to reduce the grain sizes to ultrafine grained (<500μm) or nanostructured (<100nm) level. In our present study, we attempt to produce bulk ultrafine grained Ti- 47Al-2Cr (at%) alloy using a combination of high energy mechanical milling of elemental powders to produce a very fine structured Ti/Al/Cr composite powder and consolidation of the powder using hot isostatic pressing (HIPping). It was confirmed that high energy ball milling using a planetary ball mill led to the formation of extremely fine Ti and Al layered composite structure. The thermal behaviour of the powder was studied using differential thermal analysis, and it was shown that the reactions between the Ti and Al phases in the fine structured composite powder occur at fairly low temperatures, below the melting point of the Al phase (660oC). The macrostructure and phase structure of the HIPped samples were also examined using optical and scanning electron microscopy and X-ray diffractometry (XRD). This paper is to report and discuss the results of this investigation.

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