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AbstractThe current work aims to examine the influence of various welding speeds (500, 700, and 800 mm/min) on the microstructure and mechanical characteristics of electron beam–welded Ti-6Al-4V alloy joints. The base metal microstructure was composed of a slightly elongated α phase and a transformed β phase, whereas the fusion zone (FZ) exhibited an acicular martensitic α′ microstructure. This is due to faster cooling rates in the FZ associated with electron beam welding. The welds prepared with a 800 mm/min welding speed showed higher strength and lower ductility [yield strength (YS): 959 ± 6 MPa, ultimate tensile strength (UTS): 993 ± 5 MPa, percent elongation (%El): 8] compared to those prepared with 500 mm/min (YS: 909 ± 4 MPa, UTS: 956 ± 5 MPa, %El: 11). This was due to a decrease in the width of the α-platelets in the FZ owing to faster cooling rates at higher welding speeds. For all welding speeds, samples that underwent post-weld heat treatment (PWHT) displayed a noteworthy reduction in both UTS and hardness values compared to all the as-welded samples. However, the welds at lower welding speeds showed lower strength and higher ductility (YS: 868 ± 5 MPa, UTS: 922 ± 4 MPa, %El: 13) compared to higher welding speeds (YS: 892 ± 5 MPa, UTS: 938 ± 6 MPa, %El: 9) after PWHT. This is due to the formation of the diffusional product α + β phase in the FZ, as evidenced by the transmission electron microscope results.

High Entropy Alloy (HEA) with at least 5 elements with equimolar ratios were developed to investigate the characteristics of Zr added in FeNiAlCoCrZrx (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0). HEAs were prepared by arc melting technique in Ar atmosphere and were remelted five times to ensure homogeneity. The microstructure and phase constitution of these alloys are examined by X-Ray diffraction (XRD) and Scanning Electron Microscope (SEM). The results show that addition of Zr to FeNiAlCoCr HEA resulted in multiple solid solution phases viz., BCC1, BCC2, FCC1 and FCC2 as evidenced by XRD patterns. Furthermore, presence of both BCC and FCC phases at higher Zr additions suggests that Zr did not preferentially promoted the solidification of either BCC or FCC phase. It can be observed from the FESEM micrographs that with different Zr additions, solidified microstructures of FeNiAlCoCrZrx alloys varied between completely eutectic microstructures to proeutectic and eutectic phase mixtures. From FESEM micrographs it can be suggested that different Zr contents have resulted in different solidification modes. Hardness of Zr added samples is higher compared to base HEA which is FeNiAlCoCr. It was observed that hardness values are higher when proeutectic phases were present compared to completely eutectic FeNiAlCoCrZr alloy (x=0.1).

Phase formation, microstructure, and hardness properties of FeCrNiMnCoTax and Al0.5 FeCrNiMnCoTax high-entropy alloys (HEA) have been investigated and reported. In this study, FeCrNiMnCoTax and Al0.5FeCrNiMnCoTax high-entropy alloys (HEA) were synthesized using arc-melting technique in argon (Ar) atmosphere from high purity elements (x in molar ratio, x=0.2, x=0.4 and x=0.6). Ingots from arc-melting were homogenized for 24h at 900°C in Ar atmosphere. Dominant dendritic and inter-dendritic phases were identified from the electron micrographs of these HEA. The area of inter-dendrite region increased for both FeCrNiMnCoTax and Al0.5FeCrNiMnCoTax alloys with the increasing of Ta content. The major phases in both FeCrNiMnCoTax and Al0.5FeCrNiMnCoTax alloys were identified as FCC and BCC solid-solutions. Addition of Al in Al0.5FeCrNiMnCoTax alloys has resulted in precipitation of a minor phase which was identified as FCC-TaCr2 Laves phase. As the Ta content increased, hardness of FeCrNiMnCoTax and Al0.5FeCrNiMnCoTax alloys increased from 200.34 Hv to 345.10 Hv and 385.22 Hv to 570.86 Hv respectively. Furthermore, presence of Laves phase in Al0.5FeCrNiMnCoTax alloys has resulted in higher hardness values compared to Al free sample, and this higher hardness could be attributed to precipitation strengthening effect by Laves intermetallic phase formation.

Aluminium based in-situ metal matrix composites (MMCs) have better properties and performance when compared to ex-situ MMCs. In this research, aluminium-copper (Al-Cu) alloy was reinforced with 1 to 6wt.% titanium diboride (TiB2). Al-MMCs has been fabricated with salt route reaction process at 800 °C via potassium hexafluorotitanate (K2TiF6) and potassium tetrafluoroborate (KBF4) salts. Al-Cu composites reinforced with 1,2, 3 and 6wt.% TiB2 then will be characterized their mechanical properties and microstructure. From results obtained, increased TiB2 contents will increased the value of tensile and hardness properties of Al-Cu alloy. The composites synthesized using in-situ techniques exhibit the presence a uniform distribution of reinforcement that tends to be fine and associated with a clean interface with the metallic matrix. In order to achieve a good mechanical and wear properties it is important to control Al3Ti phase formation during the synthesis of in situ Al-Cu/TiB2 composites.

Tensile and wear properties of aluminium (Al) based metal matrix composites (MMCs) was prepared by added titanium diboride (TiB2) with in-situ technique by salt route. The salts used in this research were potassium hexafluorotitanate (K2TiF6) and potassium tetrafluoroborate (KBF4). Nanocomposite samples were prepared by casting technique associated with incorporating 3 and 6 wt.% of TiB2 into matrix of Al-6wt.%Cu. Instron and wear tests machine were used to characterize the tensile and wear Al-Cu alloys properties. Results showed that increase in TiB2 content gave the high properties of tensile and wear behavior. The study indicates that TiB2 particles have giving improvement the wear performance of the Al–6wt.%Cu alloy. For a constant load and sliding speed, the wear rate decreases as a function of amount of TiB2 in the composite. The wear rate decrease with increasing in wt.% TiB2 particles for the all loads applied. However, addition of TiB2 particle to the Al–6 wt%.Cu matrix has show the coefficient value of wear decreases regardless of applied load. Study of the wear surfaces both alloy and composites by optical microscope suggests that the improvement in wear resistance is mainly due to the formation of finer groove or debris by content of TiB2.

Titanium (Ti) and its alloys are widely used in medical applications due to its superior mechanical properties and biocompatibility. Hydroxyapatite (HA), due to its similarity with teeth and bone material, is also widely used in clinical applications and orthopaedic implant manufacture. In this study, composite powers containing titanium with different wt % of HA were coated on stainless steel substrate using high velocity oxy-fuel (HVOF) spray technique. These Ti+HA coatings were characterized using XRD technique to indentify phases present in the coating. Small amount of oxide phases were identified apart from the original Ti and HA in the coatings during XRD analysis. The microstructure analysis of the coating surface using FESEM and EDX revealed dense and homogeneous coatings along with few well distributed pores.

CaCu3Ti4O12 (CCTO) is well known to have colossal dielectric constant in the range of 105.It is widely accepted that this phenomenon may be attributed to internal layer barrier capacitance (IBLC) model. The dielectric properties of CCTO were reported to be strongly dependent on the processing conditions and grain size. In this work, CCTO samples with different grain sizes were produced by varying sintering temperature in order to investigate IBLC effect on dielectric properties of CCTO. The samples were sintered at four different temperatures, (T=1100°C, 1050°C, 1000°C and 950°C). Dielectric measurements were carried out for the samples in the frequency range of 102 – 106Hz using impedance spectrometer. Electron micrographs showed that increasing temperature promoted the grain growth of CCTO while sintering. The internal crystalline defects are seen to play major role by increasing the grain conductivity in dipole formation and increased the dielectric constant of the samples.

This paper presents the characterization results of Zinc Oxide (ZnO) nanoparticles prepared by mechanochemical processing using different moles of diluents. ZnO nanoparticles of different crystallite size were synthesized by milling the precursor powders for 5 hours in a high energy ball mill with Zirconia media. NaCl was added as process control agent (PCA) to control the reaction kinetics, as final particle size of nanoZnO is influenced by the reaction rate. X-ray Diffraction (XRD) data was used to compute and analyze the crystallite size of nanoparticles and also to analyze the progress of reaction during milling process. Field Emission Scanning Electron Microscope was employed to analyze the particle morphology and size distribution of ZnO nanoparticles. Ultraviolet Visible (Uv-Vis) spectroscope was employed to analyze the optical absorption of ZnO nanoparticles. Tauc plots were used to determine the energy gap of the ZnO nanoparticles. Crystallite size values of ZnO nanoparticles are seen to be influenced by the amount of PCA and heat treatment. ZnO nanoparticles with a range of Eg (3.1 to 3.14 eV) were obtained depending on process parameters and an inverse relationship was observed between the crystallite size and the energy gap of the ZnO nanoparticles.

Synthetic Hydroxyapatite (HA, Ca10(PO4)6(OH)2) have the ability to provide the appropriate, scaffold or template for bone formation because of similar chemical and crystallographic structures to bone. The addition of 10wt. % of Ti powder in nano-HA powder was done by using ball milling. The different sintering temperatures at 1000, 1050, 1100, 1150 and 1200°C of nano-HA-Ti pallet were studied. Nano-HA-Ti pallet after vary sintering temperature were tested by hardness and compression strength tests. The optimum sintering temperature to sintered nano-Ha-Ti was at 1200°C because it gave the highest hardness and compression values which were 290.80HV and 78.49MPa. From Scanning Electron Microscopy (SEM) analyzed, nano-HA-Ti particles at 1200°C showed the attachment of nano-HA powder with Ti powder at grain boundary and some crack had form.