Study the phase transformation of Ti-6242 alloy and Determination the beta-transus temperature

Subject Areas :

علیرضا  حجاری ¹ (دانشگاه صنعتی مالک اشتر تهران)
مریم  مرکباتی ² (هیات علمی دانشگاه صنعتی مالک اشتر تهران)
رامین  حسینی ³ (دانشگاه صنعتی مالک اشتر تهران)
یاور  منصوری ⁴ (دانشگاه صنعتی مالک اشتر تهران)
مهدی  عباسی ⁵ (هیات علمی دانشگاه صنعتی مالک اشتر تهران)

Received: 2015-07-19 Accepted : 2016-12-06 Published : 2016-11-21

Keywords: Ti-6242 alloy, beta transus temperature, alpha and beta phases, Hot torsion,

Abstract :

The aim of this research is to determine the beta transus temperature of two Ti-6242 alloys and to study the effect of different amount of alloying elements on alpha and beta phase stabilization by microstructural observation and hot torsion test. Determination of beta transus temperature has an important influence on designing thermomechanical and heat treatment cycles of titanium alloys. Hence, this is an effective parameter to control mechanical properties of two phase titanium alloys. In this regard, hot torsion tests were performed at temperature range of 960 °C to 1090 °C using the strain rate of 0.001 s-1 by cooling with the rate of 0.5 °C/s. besides, in order to deduce the temperature of grain boundary alpha phase nucleation and microstructural evolution, the specimens were heat treated at temperature range of 980 °C to 1020 °C for 40 minute and water quenched. It was found that, 10 % increase in Aleq/Moeq ratio, makes a 5 °C increase in beta transus temperature of the Ti-6242 alloy. Accordingly, this temperature was estimated in the temperature range of 1000 °C to 1010 °C for these alloys. Furthermore, there is a 10 °C deviation in the hot torsion test results and microstructural analysis, which is attributed to dynamic strain-induced transformation phenomenon.

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