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.

Thermomechanical Consolidation of Ti/Al/Cr Composite (Composition: Ti-47Al-2Cr (at %)) Powders

2009 ◽  
Vol 618-619 ◽  
pp. 501-504
Author(s):  
Vijay Nadakuduru ◽  
De Liang Zhang ◽  
Peng Cao ◽  
Brian Gabbitas
Keyword(s):  
Mechanical Properties ◽  
Mechanical Milling ◽  
Composite Powder ◽  
Powder Compact ◽  
Hot Isostatic Pressing ◽  
Milled Powder ◽  
Processing Technique ◽  
Processing Conditions ◽  
Isostatic Pressing ◽  
Ultrafine Grained

The present study aims to develop a process to make ultrafine grained (UFG) Ti-47Al-2Cr (at %) alloy using elemental Ti, Al and Cr powders. The process involves mechanical milling of a mixture of the elemental powders to produce a Ti/Al/Cr composite powder, compaction of the milled powder, and consolidation of the powder compact using hot isostatic pressing (HIP) or powder compact forging. This paper is to give an overview of microstructure and the mechanical properties of the alloy samples obtained using the above processing technique. Inhomogeneous microstructures with high amounts of (α2) Ti3Al phase, along with, elemental Ti, were observed in some samples. An attempt has been made to explain the formation of (α2) Ti3Al, and elemental Ti, in the alloy and the processing conditions appropriate for the specific alloy are also discussed.

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.

Prediction of Ring Rolling Process of PM Ti2AlNb Alloy by Hot Isostatic Pressing Based on Gleeble-3800 and FE Simulation

2016 ◽  
Vol 849 ◽  
pp. 753-759
Author(s):  
Zheng Guan Lu ◽  
Jie Wu ◽  
Rui Peng Guo ◽  
Jia Feng Lei ◽  
Lei Xu ◽  
...  
Keyword(s):  
Hot Isostatic Pressing ◽  
Rolling Process ◽  
Ring Rolling ◽  
Hot Workability ◽  
Isostatic Pressing ◽  
Parameters Selection ◽  
C 50 ◽  
Ring Rolling Process ◽  
Temperature Strain ◽  
O Phase

Hot workability during hot ring rolling of Ti2AlNb alloy prepared by hot isostatic pressing (HIPing) was studied in this work. Compression results showed that the hot workability of HIP’ed Ti2AlNb was comparable to that of wrought Ti2AlNb. O phase disappeared in compression samples (conducted from 930~1030°C, ~50% total reduction) after deformation which is considered to cause elongation decrease. Finite element method (FEM) was used to predict the temperature/strain distribution during rolling process, and the results indicated that the rolling parameters were very crucial. A sound hot ring rolled billet was successfully fabricated based on an optimized rolling process. Thermal mechanical simulation and FEM are very useful tools for parameters selection during ring rolling.

Mechanical Behaviour of Ultrafine Grained Cu and Cu-(2.5 and 5) Vol.%Al2O3 Composites Produced by Powder Compact Forging

2011 ◽  
Vol 275 ◽  
pp. 170-173
Author(s):  
Aamir Mukhtar ◽  
De Liang Zhang
Keyword(s):  
Composite Powder ◽  
Powder Compact ◽  
High Energy ◽  
High Yield ◽  
High Yield Strength ◽  
High Fracture ◽  
Composite Powders ◽  
Al2o3 Composite ◽  
Ultrafine Grained ◽  
Powder Compacts

Nanostructured Cu-(2.5 and 5)vol.%Al2O3 composite powders were produced from a mixture of Cu powder and Al2O3 nanopowder using high energy mechanical milling, and then compacted by hot pressing. The Cu and Cu-Al2O3 composite powder compacts were then forged into disks at temperatures in the range of 500-800°C to consolidate the Cu and Cu-Al2O3 composite powders. Tensile testing of the specimens cut from the forged disks showed that the Cu forged disk had a good ductility (plastic strain to fracture: ~15%) and high yield strength of 320 MPa, and the Cu-(2.5 and 5)vol.%Al2O3 composite forged disks had a high fracture strength in range of 530-600 MPa, but low ductility.

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