Nb addition effect on microstructural properties of Ti-TiAl3 in situ composites produced by resistive sintering

Abstract

In this study, as an alloying element, the effect of niobium addition by 5mass% on the TiAl3 matrix in situ composites produced by resistive sintering method was investigated. As starting materials, aluminum, titanium and niobium powder with 35-44 mu m size, having 99.9%, 99.8% and 99.9% purity, respectively, were used. DSC-TG analyzes were carried out in both an open and a protective atmosphere at a heating rate of 10 degrees Cmin(-1) up to 1200 degrees C. The formation temperature of intermetallic compound for two different powders mixture determined by DSC-TG analysis was approximately 665 degrees C. The production of Ti-TiAl3 and Nb-Ti-TiAl3 in situ composites was carried out in electric activated assisted sintering system in open air with a uniaxial contact pressure of 35MPa at 2000A for 90s. SEM studies showed that intermetallic compounds have low porosity and phase transformation has not been completed and unreacted titanium is in the body as desired. In this way, it is aimed to eliminate brittleness of intermetallic phase. The distribution of elements was confirmed by EDS analysis. The presence of metallic and intermetallic phases was determined by XRD analysis. The relative density of Ti-TiAl3 and Ti-TiAl3+5mass% Nb was 98.7% and 92.1%, and the micro-hardness of materials was about 455HV and 442HV, respectively.