A comparative study of oxygen pick-up of TiHDH powder during press and sinter and loose sintering processing

Abstract: 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 pickup decreased with increasing pressure in pressed samples. These results show that press and sinter is advantageous over loose sintering where oxygen control is critical

Determination of roll compaction parameters required for high green density, defect free Ti-6Al-4V strips

Abstract: 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

Characterisation of jarosite, fly ash and clay for their possible usage in the construction industry

In this paper, the mineralogical and physical characterisation of Jarosite, Clay and Fly ash was investigated. The XRD results revealed the presence of alacranite (AsS) and jarosite (K (Fe3(SO4)2(OH)6)) mineral phases in the hazardous jarosite, while clay was composed of Kaolinite (Al2Si2O5 (OH)4), Anatase (TiO2) and Quartz (SiO2). Furthermore, Fly ash contained phases Mullite (Al4.64Si1.36O9.68), Quartz (SiO2) and Calcium oxide silicate chloride (Ca2O2Si3Cl2). The XRF results confirmed that the Fly ash used is in class F (Hazardous material) . There were hazardous elements such as As and Pb in the Jarosite sample. Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (SEM/EDS) revealed differences in surfaces morphology and EDS results were in agreement with the XRF analysis. The densities of the samples were 3.13 g/cm3 , 2.67 g/cm3 and 2.21 g/cm3 for Jarosite, clay and Fly ash respectively. There was an increase in density with the increase of the percentage of Jarosite in the mixture whereas a decrease in density was noticed with the increase of Fly ash percentage in the mixture of Jarosite and clay

Corrosion inhibition of mild steel by Poly(butylene succinate)-L-histidine extended with 1,6-diisocynatohexane polymer composite in 1 M HCl

Abstract: The ecofriendly poly(butylene succinate) extended with 1,6-diisocynatohexane composted with L-histidine (PBSLH) polymer composite was synthesized by condensation polymerization. The polymer composite was characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM-EDX). The inhibition action of the polymer composite was investigated by conventional weight loss, potentiodynamic polarization, variable amplitude micro (VASP), and electrochemical impedance spectroscopy (EIS). The maximum corrosion inhibition efficiency of 78 % was obtained at concentration level of 600 ppm. The results revealed PBSLH as a mixed type corrosion inhibitor. The thermodynamic and kinetic parameters also revealed adsorption of PBSLH on to mild surface as exothermic and the adsorption was conformed to Langmuir model. The morphology of mild steel coupons was investigated by SEM and atomic force microscope (AFM) and the results showed PBSLH to have inhibited corrosion on mild steel in 1 M HCL

Determination of the impact of strain rate on dynamic recrystallization of hot-deformed 2205 duplex stainless steel

2205 duplex stainless steel suffers poor hot workability, especially whe1981hot-deformed. This investigation aims to determine the strain rate’s effect on the material’s dynamic recrystallization after heat treatment. Secondly, to ascertain the critical strain at which the recrystallization occurs. The as-rolled material was subjected to heat treatment at 1340 °C for some time. After heat treatment, the yielded equiaxed austenite morphology was used for this investigation. Gleeble 1500™ thermo-mechanical was used as a simulant in uniaxial compression mode. The deformation temperature was set at 850 °C, with maximum strain at 0.8 and carried out at 0.001 s-1, 0.01 s-1, 0.1 s-1, 1 s-1, 5 s-1 strain rates. The microstructure of before and after heat-treatment was evaluated using a light microscope, while the critical factors (stress and strain) were determined through the stress-strain curve. It was observed that the lowest strain rate generated the maximum critical stress and critical strain at 191.99 MPa and 0.08283, respectively. However, at the highest strain rate, the maximum critical stress and critical strain experienced by the material were at 336.32 MPa and 0.17577. Overall, it was established that the applied stain rate influenced the critical strain and stress of the material. It can be concluded that dynamic recrystallization can occur at any strain rate, but the applied stress determines the extent of the phenomenon