en گروه فیزیکی و عملیات حرارتی Characterization of Physical and Thermal Properties of Materials Research Paper Research Paper Niobium addition is an appropriate approach for improvement of superalloy&rsquo;s operation. The purpose of this study is twofold: (1) to investigate on the &eta; and &gamma;^/ phase precipitations along with (2) to identify the high-temperature tensile properties in A286 and Nb-A286, as a modified type. The heat treatment of both alloys was carried out in a two-stage aging procedure at 760&deg;C for 16 h and 820&deg;C for 2 to 30 hours, following characterized by optical and Scanning electron (SEM-EDS) microscopies, differential thermal analysis (DTA) and high temperature tensile tests. The results showed that niobium addition was increased the volume fraction of &gamma;^/ phase, from 10.7% to 12%, decreased its size, from 94 to 71 nm, and rising the &gamma;^/-dissolution temperature from 987&deg;C to 1007&deg;C. Moreover, the &gamma;^/ to &eta; phase transformation was sluggishly occurred in Nb-A286 due to more stable of &gamma;^/ precipitations. Furthermore, the Nb-A286 alloy demonstrates higher mechanical properties than A286 one, approximately 100MPa improvement, which it was contributed to the much large volume fraction and finer size of more stabilized &gamma;^/ phase.<br> &nbsp; ,A286 superalloy,Niobium addition,η and γ/ phases,microstructure evaluation,hot-tensile properties 61 70 http://ijmse.iust.ac.ir/browse.php?a_code=A-10-57-4&slc_lang=en&sid=1 Reza Soleimani Gilakjani rezasoleimani@aut.ac.ir 1800319475328460011191 1800319475328460011191 No School of Metallurgy and Materials Engineering, Iran University of Science and Technology Seyed Hossein Razavi hrazavi@iust.ac.ir 1800319475328460011192 1800319475328460011192 Yes School of Metallurgy and Materials Engineering, Iran University of Science and Technology, 16846-13114 Narmak, Tehran, Iran, hrazavi@iust.ac.ir Masoumeh Seifollahi m_seifollahi@alumni.iust.ac.ir 1800319475328460011193 1800319475328460011193 No School of Metallurgy and Materials Engineering, Iran University of Science and Technology