Presently, the majority of titanium powder metallurgy components produced are sintered under high vacuum due to the associated benefits of the vacuum atmosphere. However, high-vacuum sintering is a batch process, which limits daily production. A higher daily part production is achievable via a continuous sintering process, which uses argon gas to shield the part from air contamination. To date, there has been limited work published on argon gas sintering of titanium in short durations. This study investigated the properties of thin high green density titanium strips, which were sintered at the temperatures of 1100 °C, 1200 °C and 1300 °C for a duration of 30 min, 60 min and 90 min in argon. The strips were produced by rolling of −45 µm near ASTM (American Society for Testing and Materials) grade 3 hydride–dehydride commercially pure titanium powder. The density, hardness, tensile properties and microstructure of the sintered strips were assessed. It was found that near-full densities, between 96 and 99%, are attainable after 30–90 min of sintering. The optimum sintering temperature range was found to be 1100–1200 °C, as this produced the highest elongation of 4–5.5%. Sintering at 1300 °C resulted in lower elongation due to higher contaminant pick-up.

In additive manufacturing, powder characteristics play an important role in terms of flowability and densification, which can be improved by the use of spherical powders. In this study, irregular powder was spheroidised by plasma treatment, and the powder properties were measured. Powder characterisation was conducted to determine the morphology, particle size and distribution as well as the flowability. Spherical AISI 304 stainless steel powders were produced by plasma spheroidization, and the efficiency of the spheroidisation process was evaluated. The spheroidisation process resulted in 93% efficiency with a decrease of fine particles (<63 µm) by 22%, while the all the flowability parameters of the powder improved significantly.

Shape memory alloys find application as sensors, microcontrollers or actuators. The TiPt binary system, a potential high temperature shape memory alloy due to its high transformation temperature of approximately 1000°C, displays negligible work output. This makes it unsuitable for actuator applications where work output is a prerequisite. A necessary condition for sufficient work output is for the alloy to display a critical stress for slip in austenite phase greater than detwinning stress of martensite phase. Solid solution strengthening, work hardening and precipitation hardening are possible mechanisms to improve work output. An indirect consequence of solid solution strengthening is altering of the crystal structure and the transformation temperature. This study evaluates the effect of partial substitution of Pt with V to form ternary Ti₅₀Pt_43.75V_6.25 (at.%) on the above-mentioned properties. Phase analysis and identification was done using scanning electron microscopy with energy-dispersive X-Ray spectroscopy and X-Ray diffraction. The transformation temperatures were studied by differential scanning calorimetry. Results show a three-phase microstructure with B19 Ti₅₀(PtV)₅₀ martensite as the major phase. The transformation temperature reduced with addition of vanadium in agreement with the predicted results from first-principles approach. However, the experimentally observed B19 structure did not agree with first-principles studies at 0K where B19' was the predicted stable phase.

Press and sinter is considered to be the most cost effective powder metallurgy process for producing parts. However, loose powder sintering shows to be a more promising cost effective powder metallurgy process as it entails pouring powder into a mould followed by sintering. The differences in their behaviour with respect to densification, maintaining dimensional stability and their oxidation behaviours determine the choice of their industrial applicability. Titanium has a high affinity for oxygen which in turn makes it difficult to process components from powder. It also affects the mechanical properties of products significantly; particularly in applications where ductility is imperative. The focus of this study was therefore to evaluate the oxygen pick-up of the two cost effective powder metallurgy processes (press and sinter and loose sintering). A 100 Mesh TiHDH powder was used for sintering. Sintering was performed at 1500 °C for 4 hours. The oxygen contents of the green and sintered compacts were then compared. High oxygen contents were observed in tap density powder and pressed samples. The loosely sintered components showed high oxygen pick-up after sintering while oxygen pick-up decreased with increasing pressure in pressed samples. These results show that press and sinter is advantageous over loose sintering where oxygen control is critical.

Direct powder rolling (DPR) is an unconventional powder metallurgy technique for fabricating flat mill products. It offers significant cost reduction by using low processing temperatures and reduced fabrication steps compared to ingot metallurgy. Roll compaction is the first stage in the DPR process, hence proper selection of roll compaction parameters is vital for achieving high density defect free (no visible cracks, alligatoring or centre split) green compacts. Unsuitable roll compaction parameters can result in fragile low green density strips which could be difficult to handle during subsequent processing or high green density strips with defects. The focus of this study was therefore, to determine the range of roll compaction parameters required in producing high density, defect free strips. The Ti-6Al-4V strips studied were produced by mixing 150 μm titanium hydride de-hydride powder with a 45 μm 60Al40V master alloy. The powder mix was roll compacted at varying roll gaps and rolling speeds. The compacted strips were evaluated by measuring the green strip density and thickness. It was concluded that for the Ti-6Al-4V powder studied in this work, the preferred roll compaction parameters for achieving high density, defect-free green strips are 0.3 mm to 0.5 mm roll gap with roll speeds from 3 rpm to 10 rpm.

Titanium is a light metal that has a high strength to weight ratio compared to steel. It has good corrosion resistance and is biocompatible. However, due to its high costs, its use has been limited mainly to the aerospace and medical industries. Direct powder rolling (DPR), a powder metallurgy (PM) method, is being developed with the aim of reducing the cost of producing titanium flat mill products. Critical to the success of the DPR produced products will be their ability to match or exceed the properties and performance behaviour of the equivalent products produced by wrought metallurgy. Titanium strips that are 89 % and 98 % dense were produced by DPR and their corrosion behaviour was compared to the wrought produced titanium strips. The corrosion tests were carried out in 1.75 wt.%, 2.0 wt.% and 3.5 wt.% NaCl solutions kept at 23 °C using potentiodynamic polarization. The polarization curves showed that the wrought strips were the most corrosion resistant, followed by the DPR-98 % then the DPR-89 %. The influence of pores on the corrosion behaviour was high, therefore, effort needs to be made to reduce the pores of the DPR samples.