Yahya Kemal Tür

Periodic tensile overloads in 2024-T3 Al-alloy

Crack growth due to periodic tensile overloads superposed on constant amplitude load history is studied using 2024-T3 al-alloy. The retardation associated with a single overload and the interaction between overloads controlled by the periodicity (spacing) of the overloads are examined. Overload ratios of 1.3, 1.5 and 1.65 are used. The periodicity is varied roughly between 3 and 10 000. The maximum interaction, and thus the minimum growth rate, is observed when overload spacing is around half of the delay cycles of single overload application.

Effect of Polymorphic Zirconia Phases on the Mechanical and Wear Properties of Cr3C2-NiCr Cermets

Cr3C2-NiCr type cermets are used in cutting technology for their low sintering temperatures and relatively low densities. Their high corrosion resistance at high cutting speeds and high temperatures increases the interest to these materials. In this study, a powder mixture of 75wt% Cr3C2 and 25wt% NiCr with a Ni-Cr ratio of 4/1 by weight was sintered at 1350°C as the master composite. 3 mol % Y2O3 stabilized tetragonal ZrO2 and 8 mol % Y2O3 stabilized cubic ZrO2 powders were added to study the effect of ZrO2 content on the mechanical and wear properties of Cr3C2-NiCr cermets at the same sintering temperature. SEM and EDX analysis were performed for identifying microstructures. Elastic modulus and microhardness of master and doped cermets were measured by impulse excitation technique and Vickers (HV10), respectively. Wear tests were conducted by ball on reciprocating flat method to characterize the wear properties.