ارزيابي نقش عناصر لانتانيم و اربيم بر ريز ساختار، رفتار فشاري دماي بالا و اكسيداسيون آلياژ آلومينايد تيتانيم بتا

چكيده انگليسي :

105 The effect of lanthanum and erbium on microstructure high temperature compression behavior and oxidation properties of a beta titanium aluminide alloy Morteza Hadi Morteza hadi@ma iut ac ir Date of Submission February 22 2015 Department of Materials Engineering Isfahan University of Technology 84156 83111 Isfahan Iran1st Supervisor s Name Ali Shafyei Associate Professor shafyei@cc iut ac ir2nd Supervisor s Name Mahmood Meratian Associate Professor meratian@cc iut ac irDepartment of Materials Engineering Isfahan University of Technology 84156 83111Isfahan IranAbstractThe effect of rare earth RE elements addition on the microstructure high temperaturemechanical properties and oxidation resistance of a stabilized TiAl alloy wasinvestigated by scanning electron microscopy SEM high temperature compression andisothermal oxidation tests SEM and EDS results showed that RE added alloys containeddispersed particles Most particles were rich in RE elements and oxygen therebysuggesting that solute oxygen atoms in the matrix of alloys were scavenged by RE elements With increasing RE content mean size of particles was increased however thenumber of particles reached to the maximum values at 0 2 RE corresponding tominimum interparticle spacing Afterwards as a result of particle coarsening the numberof particles was declined to the lower values Fine and closely spaced particles in themicrostructure of TNM 0 2La and TNM 0 2Er alloys led to retarding dynamicrecrystallization and higher peak flow stresses at 900 and 1000 C Also the results showedthat Er containing alloys possessed a higher flow stress particularly at 1000 C since theparticle size of Er containing alloys was less than that of La containing alloys Oxidationresistance of alloys containing 0 1 La and Er increased due to reducing diffusion rate inoxidation scale However the scale growth rate of TNM 0 2La and TNM 0 2Er werehigher than that of TNM alloy Introduction TiAl alloys are considered for high temperature applications since they offer acombination of high melting point low density high specific strength low diffusivity good resistance against oxidation and corrosion and high ignition resistance 1 A newgeneration of titanium aluminide alloys has been developed on the basis of designing aproper composition solidified via the body centered cubic bcc phase This alloydevelopment procedure leads to the significant grain refinement of the casting reducedtexture and consequently improved hot deformability 2 4 The so called TNM alloys with their overall composition range of Ti 42 45 Al 3 5 Nb 0 1 2 Mo 0 1 0 2 B allconcentrations in this work are given at can be processed by nearly conventionalforging operations thereby making the promising type of solidifying TiAl alloys 5 However lower mechanical properties at temperatures higher than 800 oC restricts thepotential applications of solidifying TiAl alloys when compared to both superalloys aswell as high niobium containing TiAl alloys Also the actual service of TiAl alloy has

هادي، مرتضي

ارزيابي نقش عناصر لانتانيم و اربيم بر ريز ساختار، رفتار فشاري دماي بالا و اكسيداسيون آلياژ آلومينايد تيتانيم بتا

استحكام دماي بالا , مقاومت اكسيداسيون