The Effects of Chromium Addition on the Mechanical Properties of a Binary TiAl Alloy at Elevated Temperatures

In the present study, the influence of chromium addition on the mechanical behavior of a binary TiAl at elevated temperatures was studied. The compositions of the binary and ternary alloys was Ti-48Al and Ti-48Al-2Cr at.% prepared and cast using vacuum are re-melting (VAR) process. Homogenizing and a post heat-treatment processes were employed and performed on the cast ingots to refine the microstructure of the samples to a refined duplex (DP) structure. Tension test at elevated temperatures was selected as a representative for the mechanical behavior of the alloys. Tensile yield and ultimate strengths and elongation of the samples were tested and measured at ambient temperature, 200, 500, 600, 700, 800 and 900°C. In the other hand, optical and scanning electron microscopies followed by energy dispersive X-ray spectroscopy (EDS) and image analyses were used to characterize the microstructure of the samples. It was found that Cr addition to about 2 at.% can increase both the strength and ductility of TiAl in ambient and elevated temperatures. The yield strength and elongation of the binary alloy were improved for about 16% and 67% respectively at ambient temperature and 25% and 125% at 900°C. The ultimate strength of both alloys was increased about 18 and 8% for binary and ternary alloys in temperature range of 500-700°C. Moreover, it was cleared that chromium can perform such effects by changing in both the microstructural and interstitial features of binary TiAl. The effects of Cr on the strength and ductility of the alloy were intensified drastically above 600°C which showed the thermally activated nature of the performed changes.

کلیدواژه ها:

Titanium Aluminide ، Chromium ، Mechanical Properties ، Alloying Design