Mohammad Masoumi

Role of Crystallographic Textures on Failure Behavior in HSLA Grade-420 Steel During Cold Rolling

The microstructural and textural evolution was analyzed during rolling at room temperature to obtain detailed information about the failure behavior in HSLA grade-420 steel. Electron backscatter diffraction measurements were carried out in both non-cracked and cracked areas after cold rolling to find a correlation between microstructural parameters (i.e., grain orientation, grain boundary characteristics and Taylor factor) and crack propagation. The results showed that the crack tended to propagate along grains oriented with {001} planes parallel to the normal direction with high Taylor factor value. The special boundaries associated with the {111}, {110} and {221} planes were indicated as crack resistance, while ∑ 5, 13a and 17a, which related to the {001} planes, were crack-susceptible. Transgranular cracking was subjected within grains with high Taylor factor, while mismatch in Taylor factor between neighboring grains could provide an easy path for intergranular crack propagation.

TEXTURAL ANALYSIS THROUGH THICKNESS OF API X70 STEEL AFTER HOT ROLLING AND POST HEAT TREATMENT

In the present study, API 5L X70 pipeline steel samples were deformed by hot-rolling cooled in air or quenched in water and subsequently tempered at different temperatures. X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) technique were used to analyze the texture evolution from the initiate state to rolling and tempering state at mid-thickness and near surface plane of all samples. The results showed that the mid-thickness region is richer in {100}//ND oriented grains known as more susceptible to crack formation and growth through. Hot deformed specimen showed dynamic recrystallization grains while quench tempered sample at 700°C evidenced recovery and grain growth.

Effect of crystallographic texture on anisotropy of SAE 970X steel under hot rolling and various post-treatments

H pluripotent stem cells (hPSCs) possess great value in the aspect of cellular therapies due to its self-renewal and potential to differentiate into all somatic cell types. A few defined synthetic surfaces such as polymers and adhesive biological materials conjugated substrata were established for the self-renewal of hPSCs. However, none of them was effective in the generation of human induced pluripotent stem cells (hiPSCs) and long-term maintenance of multiple hPSCs, and most of them required complicated manufacturing processes. Polydopamine (PDA) has good biocompatiblity, is able to form a stable film on nearly all solid substrates surface, and can immobilize adhesive biomolecules. In our study, carboxymethyl chitosan was used as a linker to orthogonally and controllably attach adhensive peptide to PDA coated cell culture plates for the culture of hPSCs. This synthetic surface was demonstrated that not only support the reprogramming of human somatic cells into hiPSCs under defined conditions, but also sustain the growth of hiPSCs on diverse substrates. Moreover, the proliferation and pluripotency of hPSCs cultured on the surface were comparable to Matrigel for more than 20 passages. Besides, hPSCs were able to differentiate to cardiomyocytes and neural cells on the surface. This polydopamine-based synthetic surface represents a chemically-defined surface extensively applicable both forfundamental research and cell therapies of hPSCs..Samples from sheets of CR 6-2 polymeric material have been exposed to gamma rays in the dose range 20-400 KGy. The modifications induced in CR 6-2 samples due to gamma irradiation have been studied through different characterization techniques such as X-ray diffraction XRD, intrinsic viscosity, refractive index and color difference studies. The results indicated that the crosslinking is the dominant mechanism in the dose range 150-400 KGy. This crosslinking destroyed the degree of order in the CR 6-2 samples associated with an increase in intrinsic viscosity values. This indicates an increase in the average molecular mass. Additionally, the non irradiated CR 6-2 sample showed significant color sensitivity towards gamma irradiation. The sensitivity in color change towards gamma irradiation appeared in the change in the blue color component of the non irradiated CR 6-2 film to yellow after exposure to gamma up to 400 KGy. This is accompanied by a net increase in the darkness of the samples.P compounds (PFCs) such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) represent a class of persistent organic pollutants (POPs) that have been detected in drinking water, waste water effluents, soil and sediments, and other aquatic environments around the globe. Recent efforts have been directed towards the design of effective remediation technology for the removal of PFCs from the environment. While there is a general consensus on adsorption-based processes as the most suitable methodology for the removal of PFCs from aquatic environments, challenges exist regarding the optimal material design of sorbents for optimal uptake of PFCs. Cyclodextrin (CDs) have been shown to form well-defined host-guest complexes with PFCs in the solution phase and the solid state according to nuclear magnetic resonance (NMR), FT-Infrared, Raman, and differential scanning calorimetry (DSC), among other results. The materials design, sorbent characteristics, and uptake performance of CD-based molecularly imprinted polymers (CD-MIPs) are generally superior compared to conventional MIPs and non-imprinted polymers (NIPs). In general, MIPs offer the advantage of selectivity, chemical tunability, high stability and mechanical strength, ease of regeneration, and overall lower cost compared to NIPs. In particular, CD-MIPs offer the added advantage of possessing multiple binding sites with unique physicochemical properties such as tunable surface properties and morphologies that vary considerably. This report provides a rationale for the design of unique polymer adsorbent nanomaterials that employ an intrinsic porogen via incorporation of a macrocycle (e.g. CD) in the polymer framework to afford adsorbent materials with tunable physicochemical properties and improved sorption capacity.This paper is concerned with the strain hardening behavior of commercially pure titanium and magnesium alloys for a wide range of strain rates. Pure titanium has described as having three stages of strain hardening behavior during compressive deformation. The stress–strain curve of pure titanium can be divided into three stages according to the strain hardening rate, and the strain hardening rate can be determined by the slope of the stress–strain curve. Mg alloy undergoes the dynamic recrystallization (DRX) during hot working process, which is a restoration or softening mechanism to reduce the dislocation density and release the accumulated energy to facilitate plastic deformation. Even though there are substantial progresses on the establishment in terms of the DRX principles and evolution with the view point of the materials science, an appropriate flow curve modeling for the finite element analysis has been deficient to take into consideration of softening behavior. A novel rate-dependent hardening model is proposed by keeping trace of deformation twins and DRX with increase in the compressive strain, which induces the variation in the strain hardening rate.