The aim of this study is to examine the effect of surface treatments involving shot blasting and paste boronizing on the microstructure, microhardness and density of 316L stainless steel. Shot blasting using glass beads was carried out prior to paste boronizing at fix boronizing temperature and soaking time of 850°C and 8 hours respectively. The results show paste boronizing produces boride layers that consist of FeB and Fe2B on the surface of 316L stainless steel with high hardness. Shot blasting on the other hand creates grain refinement on the metal’s surface which increases boron diffusion into the surface and improves the case depth of boride layers formed and also its hardness. Higher shot diameter used in shot blasting also influence in improving the case depth of boride layers produced and hardness of 316L stainless steel. The effect of shot blasting using a higher shot diameter and paste boronizing reduces the density of 316L stainless steel very slightly.
Powder carburising compound used for pack carburizing has limited potential in producing thicker case depth. Paste carburizing has proved to be an option to replace powder in conventional pack carburizing as it requires less time and temperature to diffuse carbon atoms, and thereby produce greater case depth. The correlation between case depth and mechanical properties using paste carburising is the objective of this paper where the relationship between case depth with mechanical and tribological properties using powder, paste 1:1 and paste 3:1 compounds at 1000°C for 9 hours are studied. Samples were subjected to microhardness tests, tensile tests and wear tests. Results showed paste 1:1 compound produced the highest case depth (>0.5 mm), allowing us to greater tensile strength, 6.61% and high wear resistance, 49%.
Aluminium foam tube is a metal that consists of porous medium with special characteristics such as good energy absorption, good heat transfer and high thermal conductivity. These make it suitable to be used in a wide range of applications such as in heat exchangers. The aim of this project is to identify and analyse mechanical behaviour and microstructure aluminium foam tube produced and fabricated with infiltration method with vacuum-gas. The density of aluminium foam tube was also determined and an average aluminium foam tube with porosity 50% - 80% with the average NaCl particle size 2mm, 3mm and 4mm was produced. Foams with porosity 60%-75% NaCl has higher energy absorption. These was based on foam structure, density and maximum compressive load test result.
NiTi is well known for its shape memory effect and super elasticity (SE), and is widely used in medical, dentistry and aerospace applications. For shape memory, NiTi has the ability to undergo deformation at certain temperature then recover to its original shape while SE occurs at narrow temperature range just above its transformation temperature. It shows that this material remembers its original shape and is elastic under stress. The application of nitinol as partial replacement in reinforced concrete beam for seismic resistant structures is popular due to it re-centring capability and distinctive properties. Using Shape Memory Alloy (SMA) in structures has its downsides. Hence, hybrid reinforced concrete beam with SMA was introduced to improve the structure’s ductility and energy dissipation. Hence, this research is aimed at distinguishing microstructure and mechanical properties of SMA and steel rebar. Not much is known about how SMA behaves when subjected to compression. Therefore, X-Ray Diffraction (XRD) was used to analyse if any secondary phase exists and Differential Scanning Calorimetry (DSC) test was used to analyse the phase transformation. The results showed hybrid NiTi-steel rebar can address some deficiencies of NiTi and in terms of costs. On the other hand, combining them will result in super elastic recovery, displacement ductility and strength capacity for seismic resistant design.
In this work, the effects of backbone polymer in the binder system mixed with pre-alloyed NiTi powder, on impurity contents, phase transformation temperatures and microstructures were investigated. A spherical gas-atomised pre-alloyed NiTi powder (50.3 at. %Ni) with a mean particle size of less than 22 μm and powder loading of 69.5 vol. % was used. The binder consisted of a water soluble binder system, mainly polyethylene glycol (PEG), with two different backbone binders, namely polyethylene 520 (PE 520) and poly-methyl- methacrylate (PMMA). The latter was used in the form of a powder and as an emulsion. Green parts were prepared by warm-press the feedstock into a cylindrical shape. The samples were then leached in warm water, thermally debound in Argon and finally, vacuum sintered at 1240°C for 10 h. The experimental results indicate that the oxygen content in the as-sintered condition increased to almost double than that of the powder state (from 0.08 to 0.14 - 0.16 wt. %) and the carbon increased by one third to half (from 0.06 to 0.08 - 0.09 wt. %). This consequently resulted in a shift of the phase transformation temperature to lower values and consequently broadened the reversible austenite to martensite transformation. The uptake of oxygen and carbon during the process led to the formation of the well-known Ti4Ni2Ox and TiC precipitate phases which were evident from grey-scale images of back-scattered SEM.