Effect of Heating Rate on the Phases Formation in Ti-20 wt. % Al Powder Mixture

Abstract

In this work, the effect of heating rate on the reaction temperatures in Ti-20 wt. % Al powder mixture subjected to reactive sintering process were studied and microstructure, phase composition and porosity of the reaction products were described. This system was studied because the alloys based on Ti-Al intermetallics are modern high-temperature materials and their production by common metallurgical routes is problematic. Reactive sintering could potentially replace currently used method - melt metallurgy. However, many phases form during this process and some of them are undesired. For this reason, it is necessary to describe the temperatures and other reaction conditions of their formation. One of these parameters is a heating rate. The heating rate affects reaction temperatures, phase composition as well as porosity significantly. Therefore, various heating rates were tested and the reaction temperatures were determined. The heating was recorded by optical pyrometer and one exothermic reaction was observed. It was found that this reaction is associated mainly with the formation of Ti3Al phase. Further, it was revealed that porosity decreased with increasing heating rate. This work offers data important for thermodynamic calculation and description of intermetallic phases formation during reactive sintering process.