Effect of hot forging on the structure and properties of powder equiatomic alloys based on Ti-Cr-Fe-Ni system

Abstract

Bagliuk G. A., Marich M. V., Kirilyuk S. F. Effect of hot forging on the structure and properties of powder equiatomic alloys based on Ti-Cr-Fe-Ni system. Material working by pressure. 2020. № 1 (50). Р. 187-197.

The results of the investigation of the structure, phase composition and properties of equiatomic alloys based on the Ti-Cr-Fe-Ni system obtained by sintering or hot forging of preforms from the original powder mixtures are presented. As the initial components of the charge powders of Ti, Cr, Ni, Fe, Cu and graphite were used. Three compositions of powder mixtures in the equiatomic ratio were prepared: TiCrFeNiCu, TiCrFeNiCuC and TiCrFeNiC. Preforms from powder mixtures of three compositions were sintered at 1200 ⁰C or hot forged at 1100 ⁰C in a semi-closed die using the arc press. Hot-forged samples were subjected to subsequent annealing at 1200–1300 ⁰C. During the sintering of the carbon-free alloy of the TiCrFeNiCu system, two phases of the solid solution are formed: with the structure of the matrix FCC and relatively large inclusions (with a grain size of up to 20 μm) of the BCC phase. The introduction of carbon into the charge led to the formation of additional phases in the alloy - titanium carbide TiC and chromium carbide Cr₃C₂. The significant influence of hot forging on the structure and properties of alloys is shown. In contrast to sintered alloys, the structure of the samples after hot forging, as well as subsequent annealing at 1200 and 1250 ⁰C are characterized by the presence of a specific layered structure. After annealing at 1300 ⁰C there is a spheroidization of the matrix phase, which consists mainly of rounded (ellipsoidal) grains with a size of 10÷30 μm. The highest values of hardness (HRC 62) and compressive strength (2240 MPa) are the alloy TiCrFeNiC obtained by hot forging.