پیوند نفوذی فاز مایع گذرا با استفاده از پوشش‎های نانوپراکنده‎ی Ni

Transient liquid phase diffusion bonding Al-6061 using

nano-dispersed Ni coatings

پیوند نفوذی فاز مایع گذرا با استفاده از پوشش‎های نانوپراکنده‎ی Ni

ABSTRACT

Transient liquid phase diffusion bonding (TLPDB) of Al-6061 containing 15 vol.% alumina particles was carried out at various bonding temperatures. A 5 μm thick electrodeposited Ni-coating containing 18 vol.% nano-size alumina particles was used at the interlayer. Joint formation was attributed to the solid-state diffusion of Ni into the Al-6061 alloy followed by eutectic formation and isothermal solidification at the joint interface. Examination of the joint region using scanning electron microscopy (SEM), wavelength dispersive spectroscopy (WDS) and X-ray diffraction (XRD) showed the formation of intermetallic phases such as Al3Ni, Al9FeNi and Ni3Si within the joint zone. The results indicate that the incorporation of nano-size Al2O3 dispersions into the interlayer can be used to improve joint strength.

 جهت دانلود رایگان نسخه لاتین این مقاله اینجا کلیک کنید .

 

افزودن کاربید بور پراکنده شده به مواد ترموالکتریک برپایه تلوراید بیسموت

Spark Plasma Sintered bismuth telluride-based thermoelectric

materials incorporating dispersed boron carbide

افزودن کاربید بور پراکنده شده به مواد ترموالکتریک برپایه تلوراید بیسموت

سینتر شده به روش پلاسمای جرقه ای

ABSTRACT

The mechanical properties of bismuth telluride based thermoelectric materials have received much less attention in the literature than their thermoelectric properties. Polycrystalline p-type Bi0.5Sb1.5Te3 materials were produced from powder using spark plasma sintering (SPS). The effects of nano-B4C addition on the thermoelectric performance, Vickers hardness and fracture toughness were measured. Addition of 0.2 vol% B4C was found to have little effect on zT but increased hardness by approximately 27% when compared to polycrystalline material without B4C. The KIC fracture toughness of these compositions was measured as 0.80 MPa m1/2 by Single-Edge V-Notched Beam (SEVNB). The machinability of polycrystalline materials produced by SPS was significantly better than commercially available directionally solidified materials because the latter is limited by cleavage along the crystallographic plane parallel to the direction of solidification.

 جهت دانلود رایگان نسخه لاتین این مقاله اینجا کلیک کنید .

چکیده

خواص مکانیکی مواد ترموالکتریک برپایه تلوراید بیسموت، خیلی کمتر از خواص ترموالکتریکی آنها مورد توجه قرار گرفته است. ماده Bi0.5Sb1.5Te3 نوع p پلی کریستال، به روش سینتر پلاسمای جرقه ای (SPS) از پودر تولید شد. اثر افزودن نانوذرات B4C روی عملکرد ترموالکتریکی، سختی ویکرز و چقرمگی شکست اندازه گیری گردید. مشخص شد که افزودن 2/0%  B4C اثر اندکی روی zT دارد، اما در مقایسه با ماده پلی کریستالی بدون B4C، تقریباً 27% افزایش سختی دارد. چقرمگی شکست KIC این ترکیبات به وسیله "آزمایش تیر با شیار V شکل لبه ای " (SEVNB) به صورت Mpa m1/2 80/0 اندازه گیری شد. قابلیت ماشین کاری مواد پلی کریستالی تولید شده به روش SPS، به طور قابل توجهی بهتر از مواد با انجماد جهت دار رایج تجاری است، چرا که ماشین کاری مواد با انجماد جهت دار، با کلیواژ در طول صفحه کریستالوگرافی موازی با جهت انجماد، محدود می گردد.

خواص سایش پوشش CrC–37WC–18M رسوب داده شده

Wear properties of CrC–37WC–18M coatings deposited by

HVOF and HVAF spraying processes

خواص سایش پوشش CrC–37WC–18M رسوب داده شده

توسط فرایندهای پاشش HVOF و HVAF

 

ABSTRACT

CrC–37WC–18M cermet coatings were deposited using new feedstock powders which seem to combine the properties of WC–CoCr and CrC–NiCr coatings. A conventional particle size CrC–37WC–18M powder was used as feedstock for the HVOF (high velocity oxygen fuel) thermal spraying process and a fine particle distribution was used as feedstock for the HVAF (high velocity air fuel) thermal spraying process. In order to characterize the morphology of the feedstock powders and deposited coatings SEM and X-ray diffraction were used. The microhardness of the coatings was also studied. The wear behavior of the coatings was evaluated by pin-on-disk and rubber wheel abrasion tests. The HVAF coating showed equal or even better wear resistance as compared to corresponding HVOF coatings

 جهت دانلود رایگان نسخه لاتین این مقاله اینجا کلیک کنید .

 

کامپوزیت‎های زمینه سرامیکی بافته شده

Multiscale model of woven ceramic matrix composites

considering manufacturing induced damage

کامپوزیت‎های زمینه سرامیکی بافته شده با توجه به آسیب‎های ایجاد شده‎ی تولید

ABSTRACT

Multiscale models play an important role in capturing the nonlinear response of woven carbon fiber reinforced ceramic matrix composites. In plain weave carbon fiber/silicon carbide (C/SiC) composites, for example, when microcracks form in the as-produced parts due to the mismatch in thermal properties between constituents, a multiscale thermoelastic framework can be used to capture the initial damage state of these composites. In this paper, a micromechanics-based multiscale model coupled with a thermoelastic progressive damage model is developed to simulate the elastic and damage behavior of a plain weave C/SiC composite system under thermal and mechanical loading conditions. The multiscale model is able to accurately predict composite behavior and serves as a valuable tool in investigating the physics of damage initiation and progression, in addition to the evolution of effective composite elastic moduli caused by temperature change and damage. The matrix damage initiation and progression is investigated at various length scales and the effects are demonstrated on the global composite behavior.

 جهت دانلود رایگان نسخه لاتین این مقاله اینجا کلیک کنید .