Iranian Journal of Materials Science and Engineering

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Ultrafine hydroxyapatite (HAp) powders with crystallite size in the range of 10-90 nm were synthesized by chemical precipitation process using Ca(OH)2 and H3PO4 solutions as starting materials. Molar ratio of Ca/P=1.68 was kept constant throughout the process and alkaline condition for the reaction was maintained using ammonium hydroxide. The role of raw material concentration on HAp crystallite size and morphology were investigated using X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. The results revealed that variations in crystallite size and morphology of synthesized HAp are strongly affected by the concentration of acid solution. To study the sintering behavior of HAp particles, the powders were pressed at 200 MPa using a uniaxial press. Sintering experiments were carried out at temperatures of 1100, 1250 and 1300°C with various soaking times at maximum temperatures. XRD was also used in determining thephases present after sintering process. The results indicated the decomposition of HAp into a-tricalcium phosphate (TCP) and b-TCP phases at 1300°C. The microstructure of the sintered HAp ceramics was characterized by SEM.

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The hot deformation behavior of the heat-treated AA6061 and AA 6063 aluminum alloys by T6-1, T6-2 artificial aging treatment, and O annealing treatment were studied by compression testing over a temperature range of 350–550  and strain rates of 0.005-0.1 s^-1. It was observed that the flow stresses of the studied aluminum alloys treated by the T6-1 and T6-2 heat treatments were significantly higher than those of the O annealing treatment. Moreover, the stress-strain curves of the heat-treated alloys by the T6-1, T6-2, and O heat treatments demonstrated significant softening during deformation at the lowest strain rate under any of the deformation conditions. For several strains, the activation energy of hot deformation was specified and obtained to vary significantly with strain for the heat-treated alloys by the T6-1 and T6-2 treatments. The stress-strain data calculated from a linear equation, with strain-dependent parameters, shows a great fit with the experimental data for the heat-treated aluminum alloys.

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In this study, the effects of heat treatment of aluminum alloy on the tube bending process were investigated in the rotary draw bending process. As two experimental and numerical simulation methods were used to determine the wall-thinning, ovality, and spring back for extruded, annealed, and aged AA6063 aluminum alloy tubes in different bending angles and bend radii. Numerical simulations were done by the finite element method with Abaqus software. The results indicated that in comparison with annealed and extruded parts, wall-thinning reduced whereas the amount of ovality and spring-back increased in the aged tubes. Also, in each case, the percentage of wall-thinning decreased with increasing bend radius, and the effect of bend radius was greater in the reduction of ovality from the bending angle. Investigations showed that the spring-back rate also decreased with an increasing bending angle.

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This paper presents the novel fabrication method of a three-dimensional orthogonally woven (3DW) C/C-SiC-ZrB₂ composite and the effects of ZrB₂ and SiC particles on microstructure and the ablation behavior of the C/C–SiC–ZrB₂ composite are studied. C/C–SiC–ZrB₂ composite was prepared by isothermal-chemical vapor infiltration (I-CVI), slurry infiltration (SI), and liquid silicon infiltration (LSI) combined process. Pyrolytic carbon (PyC) was first infused into the 3DW preform by I-CVI at 1050^°C using CH₄ as a precursor in order to form a C/C preform with porous media. The next step was graphitization at 2400^°C for 1hr. Then  ZrB₂ was introduced into 3DW C/C preform with a void percentage of 48 by impregnating the mixture of ZrB₂ and phenolic resin, followed by a pyrolysis step at 1050°C. A liquid Si alloy was infiltrated, at 1650 ^°C, into the 3DW C/C composites porous media containing the ZrB₂ particles to form a SiC–ZrB₂ matrix. An oxyacetylene torch flame was utilized to investigate The ablation behavior. ZrB₂ particles, along with the SiC matrix situated between carbon fiber bundles, form a compact ZrO₂-SiO₂ layer. This layer acts as a barrier, restricting oxygen infiltration into the composite and reducing the erosion of carbon fibers. The findings were supported by FESEM imaging and further confirmed through x-ray diffraction and EDS analysis. The addition of ZrB₂ to the C/C-SiC composite resulted in a lower mass and linear ablation rate; 2.20 mg/s and 1.4 µm/s respectively while those for C/C-SiC composite were 4.8 mg/s and 6.75 µm/s after ablation under an oxyacetylene flame (2500°C) for 120 s.
 

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The investigation of the mechanical response and microstructural evolution of engineering materials at the micro-scale under macro-scale loading poses a significant challenge in mechanical engineering, particularly in the fields of material forming and materials science. This critical has been addressed using a computational crystal plasticity tool known as DAMASK (Düsseldorf Advanced Material Simulation Kit). DAMASK is a multi-scale computational framework developed for modeling the deformation of crystalline materials by employing the principles of continuum mechanics and crystal plasticity. This software is widely recognized within the scientific community for its high flexibility and capability to simulate complex material behavior under various loading conditions. In this study, the DAMASK code—a finite element crystal plasticity software—was employed to analyze a representative volume element (RVE) containing 1000 grains under tensile loading. By applying a random initial texture to aluminum grade 1050, the microstructural evolution of the material under the specified loading conditions was evaluated. The results indicate the formation of <111> and <100> fiber textures in the (111) crystallographic plane of the FCC-structured material, which are consistent with observations obtained from EBSD experiments.