Effect of Forging Temperature on Microstructure Evolution and Tensile Properties of Ti-17 Alloys

Abstract

In this study, the microstructure, tensile strength, elongation, and reduction of area of near-¢ Ti alloys (Ti-17) were investigated after being subjected to solution and aging treatments. Ti-17 was forged at temperatures between 700 and 850°C followed by air cooling. Then, the forged Ti-17 was subjected to solution treatment at 800°C for 4 h followed by water quenching and aging treatment at 620°C for 8 h followed by air cooling. Tensile tests were performed at room temperature, 450°C, and 600°C. The change in microstructure at different forging temperatures was exhibited by only the volume fraction and morphology of the grain boundary (GB) ¡ phase. That is, a granular GB ¡ phase was formed in the samples forged at 700 and 750°C. Moreover, a film-like GB ¡ phase was formed in the samples forged at 800 and 850°C. The tensile strength was the same for all the tested samples, indicating that the microstructure has little effect on the tensile strength. The elongation and reduction of area increased with decreasing volume fraction in the GB ¡ phase. It is considered that the film-like morphology slightly improves ductility.

Effect of microstructure on tensile properties of Ti-17 alloys forged using a 1500-ton forging simulator

“…The microstructures of the samples forged at various forging temperature are shown in Fig. 4 [11]. It was found that the forging temperature affected only the morphology of GB alpha phase; that is, the granular shape alpha phase was observed along grain boundaries for the samples forged at 700 and 750 ˚C.…”

“…The microstructure evolution was clarified by observation of the microstructure of as-forged, solution-treated and aged samples [11]. It was found that the beta phase exhibited and the alpha phase formed at only grain boundary during forging.…”

“…The microstructures of as-forged samples and the solution treated and aged samples using the 1500 ton forging press were observed and the prediction models were improved to describe them precisely. The effect of the microstructure factors such as the volume fraction of the primary and secondary alpha phase and the grain size and the aspect ratio of the beta phase on tensile properties and fatigue was also investigated for samples forged using 1500 ton forging press, solution treated and aged materials [11,12]. These models were connected each other as a subroutine and inserted to FEM software to simulate microstructure and tensile strength.…”

Recent activities of titanium research and development in Japan

“…Next, the forged specimens were solution treated and aged (STAed), their microstructure evolution was investigated, and a prediction model for STA was established [6]. The tensile strength and fatigue life of the specimens forged using the 1500 t press and STAed were tested to understand the microstructural factors that control the mechanical properties, and a prediction model for tensile strength was established [7,8]. To apply the prediction model to the 1500 t forging press, coefficients of friction and thermal transfer were determined by comparing experiments conducted using the hot forging emulating system and Finite Element Method (FEM) [9].…”

Correlation between Solution Treatment Temperature, MicroStructure, and Yield Strength of Forged Ti-17 Alloys

“…In previous studies, we investigated the dependence of the microstructure evolution of Ti-17 alloy on the forging conditions, along with the corresponding tensile properties [25,26]. Cylindrical Ti-17 ingots with a diameter of 134 mm and height of 192 mm were isothermally forged using a 1500 t forging press and then air-cooled.…”