Microstructural evolution and nano-mechanical properties of Ti-Al-based alloys synthesized by laser in-situ alloying

^a Department of Chemical, Metallurgical and Materials Engineering, Tshwane University of Technology, P.M.B. X680, Pretoria, South Africa
^b Laser Materials Processing Group, National Laser Center CSIR, Pretoria 0001, South Africa
^c Department of Mechanical Engineering Science, University of Johannesburg, Auckland Park Campus, Johannesburg, South Africa

^* Correspondence: lrkanyane@gmail.com
^* Correspondence: MTlotleng@csir.co.za

Abstract

Developing titanium aluminides (Ti-Al) based alloys by means of Laser Engineered Net Shaping (LENS) in-situ manufacturing yields attractive properties as compared to other fabrication methods. Ti-Al alloys have attracted much attention for high-temperature performance in gas turbine and automobile applications because of their attractive properties such as low density, high strength, high stiffness, and good oxidation resistance. In this work, laser in-situ fabricated Ti-Al-2Cr (Sample C3), Ti-Al-3Cr (Sample C1) and Ti-Al-4Cr (Sample C2) alloys were developed and the compositional effect on morphological evolution and nano-mechanical properties were investigated. The developed alloys were heat treated to 1350°C and air-cooled. The microstructural evolution was characterized using the scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). Anton-Paar equipment was used to analyze the nanoindentation properties (hardness, elastic modulus and stiffness) and MatLab software was utilized to analyze the stress-strain behaviour of the alloys from the nanoindentation load-displacement curve. The results showed that normalizing heat-treatment played an important role in homogenizing the alloys and there was a significant decrease in nanoindentation hardness, stiffness and modulus of elasticity after heat-treatment.