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Effect of Lithium Addition on Microstructure, Texture and Mechanical Properties of Al-Mg-Si Alloys

Thesis Info

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Author

Din, Shamas Ud

Program

PhD

Institute

Pakistan Institute of Engineering and Applied Sciences

City

Islamabad

Province

Islamabad

Country

Pakistan

Thesis Completing Year

2015

Thesis Completion Status

Completed

Subject

Applied Sciences

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/6798/1/Shamas_ud_Din_2015_Materials_Engineering_PIEAS_ISD.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676725977533

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A number of Li containing 6××× alloys were prepared and characterized for potential aerospace applications. The alloys composition in weight percent were, Al-0.5Mg-0.2Si-xLi and Al-0.9Mg-0.5Si-xLi, with x = 0,1,2,3 respectively. Zirconium additions were also made in the latter alloy system. In the first phase the effect of Li on low alloy group (LAG alloys) was studied. The microstructure and mechanical properties changed substantially with Li. SEM/EDX and XRD analysis revealed that Li addition promoted the formation of Al3Li phase which strongly affected the mechanical properties. The alloy containing 3% Li showed maximum hardness after aging. In the second step the aging response of Al-0.5Mg-0.2Si-3Li alloy in W, T6 and T8 conditions was evaluated. Cold reductions, through rolling were made up to 10 - 60 % followed by aging at 175 °C for 2 - 12 hrs. Maximum hardness was achieved after 60 % cold work and 10 hours of aging time, attributed to the fine Al3Li precipitates. In the third part, the LAG alloys were investigated for micro-texture evolution. The intensity of the deformation texture increased with Li content, while Li helped in reducing texture strength after aging. Significantly low fraction of å3 type coincident site lattice (CSL) boundaries was observed for all Li containing alloys, as compared to the Li-free compositions in the aged condition. In the fourth phase, the effect of Li/Si and Li/Mg ratio on LAG and High alloy group (HAG alloys) was investigated. Inverse pole figure (IPF) maps, TEM/EDX and XRD indicated that Li addition above 1 wt.% promoted the formation of Al3Li precipitates. It was concluded that Li/Mg ratio played a more effective role in comparison with Li/Si ratio for enhanced aging response. In the final phase, HAG alloys microalloyed with Zr were extruded, quenched and aged. The alloy density was reduced up to 7.8% in comparison to the Li-free alloy while UTS increased by 62% with 3% Li addition. EBSD data revealed that Li effectively reduced the grain size of the modified alloys. The hardness, YS and UTS first decreased for 1 wt.% Li addition and then increased with increasing Li content from 2 to 3 wt.% at the expense of ductility. After T6 condition, the texture intensity of the extruded alloys increased with Li content, contrary to the observation made for the rolled alloys that did not contain Zr. This was attributed to the presence of Al3Zr dispersoids in extruded HAG alloys. Finally, a synergistic effect of Li and other alloying elements in 6××× alloys on mechanical properties and texture is obtained.
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سوکھا کم نئیں ہوندا۔۔۔

سوکھا کم نہیں ہوندا اے عشق اندر، آس یار دے بوہے دی لا رکھنی
چیہہ وٹ کے درد نوں سہہ جانا، پنڈ دکھاں دی سر تے چا رکھنی
غم ہجر فراق نوں جھل کے تے، رو رو کے تے راتیں یاد کرنا
اگوں سوہنیاں دی مرضی اپنی اے، کیہدے نال سلام دعا رکھنی
خون جگر دا تلی تے رکھ کے تے، ہتھ یار نوں جا وکھا دینے
اگوں سودے نے بے نیازیاں دے، نہ کوئی ہمدردی نہ وفا رکھنی
چادر کھیس موہڈے اتے رکھ لینا، بکل مار کے کندھاں دے نال بہنا
ویکھو عشق دے کیسے قانون وکھرے، جرم ہور تے ہور سزا رکھنی
درد دکھ فراق دے لکھ سہنے، ہوکے بھرنے یار دے ہجر اندر
آس رکھ لینی، آس توڑ دینی، اینویں جندڑی گھول گھما رکھنی
اکھاں نال بہار حنیف دی اے، اکھاں نال پریت دا لطف ہوندا
اکھاں والڑے قدر ہی جاندے نیں، اکھاں نال ہے کیویں وفا رکھنی

The Status of Medical Manuscripts by Muslim Scientists at Islamia College Peshawar Library

The subject of Medical Science was the central part in the history of Muslim culture. The muslim scientists have produced extensive medical literature. This treasure of knowledge has been preserved in different public and private institutions throughout Khyber Pakhtunkhwa, particularly on Peshawar University Campus libraries. One among them is Islamia College Peshawar Library, which contains some of the rare medical manuscripts.  This paper will highlight the current status of these manuscripts present in Islamia College Library Peshawar. The paper will also reveal the metadata of these manuscripts.

Study of Rare Earth and Transition Metals Co-Substituted Y-Type Hexaferrites for High Frequency Applications

The effects of rare-earth (Nd, Gd, Dy, Pr) and transition metal (Ni, Co) ions on Sr-Ba-Cu and Sr-Ba-Zn based Y-type hexaferrites have been investigated. Four series having nominal composition (1) SrBaCu2-xNixNdyFe12-yO22 (2) SrBaCu2-xCoxGdyFe12-yO22 (3) SrBaZn2-xCoxDyyFe12-yO22 and (4) SrBaZn2-xNixPryFe12-yO22, with x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0 and y=0.0, 0.02, 0.04, 0.06, 0.08, 0.1. Sol gel auto-combustion route was employed to prepare these four series. Thermal analysis was employed to study the thermal decomposition process and showed that the pure hexagonal phase was developed after annealing at 950 °C. The crystallite size obtained for all the samples was in the range of 11-22 nm. There was overall increase in lattice parameters by doping with rare-earth and transition metal ions. However, the increase was non-linear. The non-linear trend in lattice parameters was due to the large ionic radii of dopant cations. The bulk density (ρm) obtained for all the samples were much lower than the X-ray density (ρx). The absorption bands displayed by the spectra of FTIR correspond to the tetrahedral and octahedral sites which display signature of hexagonal structure for all the samples. Dielectric behavior was explained on the basis of conduction mechanism through hopping of electrons between Fe3+ and Fe2+ ions and Maxwell-Wagner model. Nyquist plots confirmed the grain boundary contribution in all the prepared Y-type nano hexaferrites samples exhibiting single semicircle. Q values obtained were high and observed above 2.5 GHz. The values of quality factor highlight the possibility of tailoring the operational frequency through compositional control. This suggested the utilization of these materials in Multi-layer chip inductors (MLCIs) at high frequency. The variation in magnetic parameters was discussed in terms of strength of exchange interactions and cations occupancy on different sites. Saturation magnetization and coercivity were found quite high for Dy-Co doped Sr-Ba-Zn hexaferrites and Gd-Co doped Sr-Ba-Cu hexaferrites which suggested the possible utilization of these materials in making permanent magnets. Sr-Ba-Cu based hexaferrites doped with Nd-Ni and Sr-Ba-Zn based hexaferrites doped with Pr-Ni indicated soft characteristics and proved to be suitable for utilizing the prepared hexaferrite materials in fabricating electromagnetic materials and sensors working at higher frequencies. The findings summarized here in current research are useful for exploring the significance of rare-earth transition metal co-doping on the transport properties of prepared Y-type nano-hexaferrites and provide a way for utilizing these hexaferrite materials in making permanent magnets and electromagnetic devices operating at higher frequencies.