Papers by Author: Vijay Nadakuduru

Abstract: Consolidation of titanium and titanium alloy powders using thermomechanical powder metallurgy (TPM) processes (powder compact forging, extrusion and rolling) is one way that can lead to cost-effective production of high value-added consolidated titanium and titanium alloy products such as near-net shaped components, tubes and plates. This paper provides an overview of the quality, microstructure (to limited depth), porosity level and mechanical properties of disks produced using open die forging of powder compacts of CP titanium and Ti-6Al-4V alloy powders. The general materials science principles underlying the relationships between processing conditions, microstructure and the mechanical properties of the disks made by using the powder compact forging are discussed.

Abstract: 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.

Abstract: 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.