Magnesium alloys with a various content of zinc (Zn) and yttrium (Y) were extruded with an extrusion ratio of 1:18 at 350 °C. The alloying elements in these Mg alloys formed a long period stacking ordered (LPSO) phase, which was characterized by transmission electron microscopy (TEM). The microstructure of the alloys was further examined by light microscopy and scanning electron microscopy (SEM), where LSPO phase in all alloys was found to be elongated along the extrusion direction (ED). Mechanical properties of the extruded alloys were investigated during compression loading at various temperatures between room temperature and 350 °C at a constant strain rate of 10-3 s-1. Concurrently with the deformation tests, the acoustic emission (AE) response of the specimens was recorded, in order to reveal the active deformation mechanisms. The conclusions of the AE experiments were proved by the microstructure investigations.
ZnAl15 alloy is one of the many non-ferrous alloys intended for corrosion protection coatings of steel applied by thermal spraying process. ZnAl15 alloy wires for thermal spraying are manufactured by the wire drawing process from wire rod which is manufactured using continuous casting and rolling process. In various manufacturing technologies the wire rod may be subjected to heat treatment at elevated temperatures, in order to obtain desired level of mechanical properties. Applying different times and temperatures of heat treatment causes phase transformations and changes in the grain size, which affects macroscopic properties of the alloy. The aim of the research is to determine the impact of the alloy exposure to temperatures in a range from 150°C to 300°C and time intervals between 1 and 6 hours on microstructure, electrical resistivity and tensile properties. Authors are grateful for the financial support of this research provided by The National Centre for Research and Development - Research Project No. POIR.01.01.01-00-0361/17.
In recent years zinc alloys have attracted more and more researchers’ attention as a metallic material with a potential application on biodegradable implants, like fixation of small bones or stents. Their ease of manufacturing, biocompatibility, and proper corrosion rate make them a good candidate for the medical use. The main challenges for use pure zinc are poor mechanical properties and susceptibility to recrystallization at room temperature. Mentioned implants should exhibit the required mechanical strength and integrity with damaged tissue during its regeneration time and after that it should completely dissolve in the human body. Based on the literature review it can be stated that by the introduction of the biocompatible alloying elements and the use of plastic deformation processes, the mechanical properties of zinc alloys can be effectively improved.
As a part of the research, the effect of silver and zirconium additions on grain refinement in zinc alloy was examined. According to Hall Petch relation, the smaller grain size leads to enhanced yield strength. The EBSD analysis was carried out on samples of Zn-Ag-Zr alloy after indirect extrusion at 250°C to analyze grain size and microstructure of investigated alloy. The properties were evaluated based on the uniaxial tensile, compression and Vickers hardness tests with the reference to results obtained for binary system alloy. In addition, the static immersion test was performed in Hank’s solution. It was observed that simultaneous addition of Ag and Zr contributes to forming intermetallic phases in zinc matrix, followed by grain refinement and improvement of mechanical properties in the investigated alloy.
An investigation has been carried out on making and characterization of ZA-27 alloy treated with zinc oxide nanoparticles. This was aimed at developing high performance ZA-27 alloy with low density. The particle size and morphology of the zinc oxide (ZnO) nanoparticles were investigated by Transmission Electron Microscope (TEM) and the elemental composition was obtained from Energy Dispersive Spectroscopy (EDS) attached to TEM and X-ray fluorescence spectroscopy (XRF). ZA-27 nano alloy samples were developed using 0, 1, 2, 3, 4 and 5 wt% of ZnO nanoparticles by induction furnace casting technique. Mechanical properties and Microstructural examination were used to characterize the composite samples produced. The results show that hardness and ultimate tensile strength of the composite samples increased progressively with increase in weight percentage of ZnO nanoparticles. Increase in Ultimate tensile strength (UTS) of 10.2%, 21.1%, 22.3%, 35.5%,33.4% and increase in hardness value of 8.2%, 14.8%, 21.7%, 27.9%, 27.1% were observed for Zn -27 alloy treated with 1 wt%, 2 wt%, 3 wt%, 4 wt%, and 5 wt% ZnO nanoparticles respectively in comparison with untreated alloy. It was generally observed that alloy containing 4 wt% of treated has the highest tensile strength and hardness values. However, the fracture toughness and percent elongation of the composites samples slightly decreased with increase in ZnO nanoparticles content. Results obtained from the Microstructural examination using optical microscope and Scanning Electron Microscope (SEM) show that the nano particles were well dispersed in the ZA-27 alloy.
Phase transformations in metastable β titanium Ti-15Mo alloy were investigated by several indirect techniques, such as: electrical resistance, dilatometry, transmission electron microscopy. In order to directly observe occurring processes in-situ direct X-ray and neutron diffraction were employed during linear heating and confirmed statements based on results of indirect methods, such as: the decrease of volume fraction of ω phase during heating at low temperatures (up to 250 °C), complete dissolution of ω phase at 560 °C and precipitation of α phase without ω particles serving as its direct precursors. X-ray diffraction experiment allowed to determine relative evolution of the size of ω particles while phase fraction evolution was derived from neutron diffraction. The volume fraction of β phase at room temperature is about 60 %. The volume fraction of ω phase during heating with the heating rate of 5 °C/min reaches its maximum value of 45 % at about 400 °C. The maximum amount of the volume fraction of α phase during the same experiment was 11 % at about 650 °C.
The so-called metastable beta titanium alloys are promising materials for joint implant production due to combination of high strength with low Young’s modulus. Low stiffness eliminates the stress-shielding effect of the implant in the bone, that arises when the difference between Young’s modulus of a bone and the implant is large. Alloy with composition Ti-35Nb-6Ta-7Zr-0.7O shows Young’s modulus of 80 GPa and yield strength over 1100 MPa, after thermomechanical processing. The Young’s modulus, however, rises upon aging at elevated temperatures, which is caused by alpha phase precipitation. Determination of beta phase stability is therefore crucial for designing the final processing route. The material was tested in several aged conditions by microhardness measurements and by scanning electron microscopy to determine phase composition and microstructural changes.
The main aim of this study was to determine the mechanical properties of the Al5Ti5Co35Ni35Fe20 alloy. Investigated alloy were characterized by γ structure in as-cast and γ/γ’ homogenized state. Subsequent annealing for 20 h at 1100°C provides to obtain a single solid solution. To evaluate the aging effect on the microstructure and the mechanical properties short aging (700 °C for 4 hours) and prolonged aging for 7 days at 650 °C, 700 °C, 800 °C and 900 °C were performed. Afterwards, samples were subjected into the uniaxial tensile tests at room temperature and the microstructural analyses by means of scanning electron microscope.
ACKNOWLEDGEMENTS: This work was supported by the Polish National Science Centre [grant number 2017/25/N/ST8/02542].
Slags are second sources of metals. The use of macadamia nutshells as reductant has not been investigated in the slag recycling industry. The current study investigates the use of raw macadamia nut shells in the recovery of valuable metals from slags. A slag containing copper, cobalt, iron and zinc has been used. Both the feed and products were characterized using XRF, XRD and SEM. The basicity of slag was increased through the addition of calcite. A graphite crucible was used and placed in a tube furnace. Experiments were conducted at 1400 oC and carbon monoxide was blown into the furnace to enhance the reducing atmosphere. The furnace was kept at the set temperature for two hours and was switched off to slowly cool down. Results revealed that it is possible to use the macadamia nutshells in the slag recycling industry with attention paid to the final basicity for a better immiscibility of the final slag and the metal. A comparison of results obtained when the same slag was reduced using coke showed that the quality of the metal obtained using macadamia nutshells are not as good as when coke is used. However there is great prospect for the future