اتصال نانو كامپوزيت Al/Al2O3 به روش فاز مايع گذار

چكيده انگليسي :

Joining of Al Al2O3p Nanocomposite by Transient Liquid Phase Sayyed Shahab Sayyedain ss sayedain@ma iut ac ir March 4 2012 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiDr Hamid Reza Salimi Jazi Assis Prof Supervisor E mail hrjazi@cc iut ac irDr Mohammad Reza Toroghinejad Assoc Prof Supervisor E mail toroghi@cc iut ac irAbstractTodays aluminum matrix composites are widely used in many industrial applications such as aerospace automotive electronics due to their good properties such as high strength to weight ratio low density highhardness and good oxidation and wear resistance These properties can be superior when the compositesstructures become nanostructure Challenges in joining of nano structured aluminum matrix composites toproduce complex shape structures limits their application In the current study the joining mechanism ofaluminum matrix nanocomposite reinforced by nano metric alumina particles was investigated Transientliquid phase TLP diffusion bonding method was used for joining and the effect of joint parameters such astemperature and time on joint properties was investigated Al 10 wt Al2O3 nanocomposite samples wereproduce by hot pressing using nanocomposite powders produced by mechanical alloying A thin layer ofcopper coating was deposited on joining surfaces of the composite by electrodeposition technique The TLPbonding was carried out at various bonding temperature and time In order to investigate of microstructuralstudies of powder nanocomposit bulk nanocomposite components and the bonded interfaces at different jointconditions optical microscopy was used Evaluation of nanocomposite powder particles morphology andbulk components microstructure as well as the joint fracture surfaces was carried out by scanning electronmicroscopy SEM In order to investigate of the aluminum crystallite size in the powder and nanocompositebulk components after hot pressing the X ray diffraction pattern was used Shear strength of the bondedjoints was evaluated by means of a specially designed fixture in a tension testing machine with a loadingspeed of 1 mm min In order to determine the micro hardness profiles across the bonded interface micro hardness test was carried out applying load of 50 g Results showed that the average crystallite size ofnanocomposite powder was about 52 nm and there were no significant changes in the crystallite size duringhot pressing Some microcracks and porosities were found in the joint areas that were filled from Al phaseand fine CuAl2 precipitated particles By increasing the joint temperature the filled areas were increased dueto a higher amount of molten material produced during joining Moreover by increasing the joiningtemperature the amount of CuAl2 precipitated particles were reduced resulting in reduction of the hardnessof the Al phase in the joint area The maximum shear strength 85 percent of the base metal shear strength was acheived at the bonding temperature and time of 580 C and 60 minutes respectively High actualcontact between the liquid phase and base metal due to porosity and high diffusion coefficient of copper innanostructured base metal are the main factors for the low isothermal solidification time in thenanocomposite compared to conventional aluminum matrix composites Investigation of fracture surfacesafter shear strength tests showed shear dimples CuAl 2 precipitated particles and porosities At low joiningtemperatures joint strength increased by increasing time At high joining temperatures joint strengthdecreased by increasing time due to decreasing CuAl2 particles in the Al phase Keywords Aluminum matrix composites Nanocomposite Mechanical alloying Transient liquidphase Inter layer Hot press Microstructure Nanostructure Isothermal solidification

سيدين، شهاب

اتصال نانو كامپوزيت Al/Al2O3 به روش فاز مايع گذار

آسياب كاري مكانيكي , لايه واسطه , پرس گرم , ريز ساختار , انجماد هم دما