Effect of cold deformation and heat treatment on microstructure and mechanical properties of TC21 Ti alloy

In the present research work on TC21 titanium alloy(6.5 Al-3 Mo-1.9 Nb-2.2 Sn-2.2 Zr-1.5 Cr), the effects of cold deformation, solution treatment with different cooling rates and then aging on microstructure, hardness and wear property were investigated. A cold deformation at room temperature with 15% reduction in height was applied on annealed samples. The samples were solution-treated at 920 ℃ for 15 min followed by different cooling rates of water quenching(WQ), air cooling(AC) and furnace cooling(FC) to room temperature. Finally, the samples were aged at 590 ℃ for 4 h. Secondary α-platelets precipitated in residual β-phase in the case of solution-treated samples with AC condition and aged ones. The maximum hardness of HV 470 was obtained for WQ + aging condition due to the presence of high amount of residual β-matrix(69%), while the minimum hardness of HV 328 was reported for FC condition. Aging process after solution treatment can considerably enhance the wear property and this enhancement can reach up to about 122% by applying aging after WQ compared with the annealed samples.

Recovery of Cassiterite and Topaz Minerals from an Old Metallurgical Dump, Eastern Desert of Egypt

Huge amounts of tailing dumps as a result of mines’ blasting operations were impacting economic and environmental problems. Evaluation of one of these tailing dumps of the Eastern Desert of Egypt showed the presence of reasonable amount of cassiterite mineral reaching 0.199% SnO2. The mineral cassiterite was found as finely disseminated particulates, reached to 5 microns, within varieties of quartz-feldspar-hornblende-biotite granitic formations. In the present study, the processing regime considered from the beginning the alignment between reaching cassiterite mineral liberation size, and its extreme brittleness character. Stirring ball milling technique was applied to produce −0.51 mm product with minimum fines as possible, which was left aside for a separate study. The ground product −0.51 + 0.074 mm was subjected to joint shaking table/dry high intensity magnetic separation techniques after splitting it into two fractions, −0.51 + 0.21 mm and −0.21 + 0.074 mm. Each fraction was separately subjected to “Wilfley” shaking table. At optimum conditions, a shaking table concentrate was obtained with 0.29% SnO2 and an operational recovery reached 96.94% from a feeding contained 0.19% SnO2. The heavies and the two middling products after shaking table were directed separately after dryness to dry high intensity magnetic separation using “Eriez” rare earth roll separator, meanwhile the light fractions were rejected. Mathematically designed experiments were applied to optimize the separation process. At optimum conditions, a final cassiterite concentrate was obtained with 11.25% SnO2, and an operational recovery 94.08%. In addition, a topaz mineral concentrate was separated at splitter angle 65˚.

Doping effect of SrZrO_(3) on KNLN ceramics structure and their dielectric properties

In this work,lead-free systems;(1-x)(K_(0.465)Na_(0.465)Li_(0.07))NbO_(3)–xSrZrO_(3)(x=0,0.005,0.050,0.095 and 0.14)were synthesized by the conventional solid-state reaction technique.XRD,SEM,densification parameter as well as dielectric parameters of the obtained KNLN ceramics were investigated.XRD analysis showed the formation of orthorhombic perovskite structure in all investigated specimens.SrZrO_(3)(SZ)inhibited the grain growth and increased the distribution of grains uniformly in the microstructure.In addition,SZ changed the crystalline system of KNLN ceramics abnormally.As a consequence,the permittivity,dielectric loss as well as AC conductivity decreased remarkably.The ceramics of x=0.005 are characterized by low conductivity(10-10 S/cm),low dielectric loss(0.005)and relatively high permittivity(34).They can be useful for the electrical capacitors fabrication and filtering out noise from signals in resonant circuits.At frequencies lower than 105 Hz,DC conductivity and separation of the charges at the interfaces were found to dominate the electrical behavior of ceramics,whereas at higher frequencies,a faster or dipole polarization may become more dominated.A broad peak has been observed in the imaginary part of electric modulus revealing to the non-Debye dielectric relaxation behavior.Quantum mechanical tunneling(QMT)was found to be the most suitable to characterize the electrical conduction mechanism in the ceramic compounds.