Abstract
Titanium and titanium alloys are considered to be one of the most significant advanced materials used in the aerospace, structural, chemical, marine, oil and gas, petrochemical, medical and other industries today. This can be attributed to its comprehensive properties such as excellent corrosion resistance, high heat resistance, specific strength and fracture toughness, good low temperature toughness and low density. Due to the high cost of producing titanium metal through the conventional way of using Ingot Metallurgy (IM), alternative cost effective methods of such as Powder Metallurgy (PM) have been developed. There are several forms of powder metallurgy processes but the process that was used for the research work is that of Direct Powder Rolling (DPR). This process uses powder as a feedstock for a roll compaction mill. The rolling mill consolidates the feedstock into a green strip that has some form of ductility.
DPR of Ti and titanium alloy powder has been successfully demonstrated by CSIRO as well ADMA Incorporated using different processing techniques which contain multiple fabrication stages. The proposed research work was aimed at evaluating an alternative DPR processing route containing far less fabrication stages which leads to a further reduction in cost whilst achieving mechanical properties equivalent to those of wrought materials. The aim of this work was to produce roll compacted Ti6Al4V strips though roll compaction and sintering as well as to study the effect of thermal processing of the strips on density, microstructure and mechanical properties. The objectives of this work were therefore to define roll compaction parameters that will achieve green strips of 85 ±2% theoretical density of Ti6Al4V, define sintering parameters that will produce a perfectly homogeneous strip with a high final sintered density of ≥99% theoretical density and to achieve mechanical properties equivalent to those of Ti6Al4V sheets as per ASTM B265-15 standard specification for Ti and Ti alloy strip, sheet and plate.
The roll compacted strips were sectioned and characterised for density using the volumetric density determination method. The strips were sintered at temperatures of 1200, 1300 and 1400°C with holding times of 2, 3 and 4 hours in a Carbolite tube...
M.Tech. (Engineering Metallurgy)