Effect of hot rolling temperature on microstructure evolution, deformation texture and nanoindentation properties of an intermetallic Ti-43Al-9V-0.2Y alloy

摘要

In this paper, microstructure evolution, deformation texture and nanoindentation properties of an intermetallic Ti-43Al-9V-0.2Y (at. %) alloy have been investigated after hot rolled in alpha+beta+gamma (R#1) and beta (R#2) phase field regions. The primary components of sample R#1 are (beta+gamma) mixture and (a2+y) lamellar structure. With the temperature increases to 1250 degrees C, the microstructure of R#2 shows a new characteristic of martensitic alpha(2) and acicular gamma phase. And gamma phase has different precipitation mechanisms by hot rolling at 1200 degrees C and 1250 degrees C. In R#1, gamma phase is obtained through three provenances, which are the precipitating from beta to form (beta+gamma) mixture, the precipitating from a phase to form (alpha(2)+gamma) lamellar structure, and the remnant gamma phase during cooling from alpha-beta+gamma phase field. However, for R#2, gamma phase always nucleates and grows within beta matrix. Meanwhile, microstructure evolution of R#2 is discussed. In addition, the increase in rolling temperature also results in a significant change of the fiber texture. Comparing with gamma phase, beta phase has the stronger texture, which is due to the formation of gamma grain along the K-S orientation relationship in p phase. In R#1 state, beta phase exhibits a typical {121} < 1-11 > texture, while gamma phase shows {031} <-5-13 > and {112} < 1-10 > texture. Aiming at R#2, beta phase displays {010} < 100 > cube texture, and y phase has {-215} < 5-53 > and Goss {110} < 001 > texture. The hardness (H) and reduced elastic modulus (Er) are investigated by nanoindentation. The (beta+gamma) mixture structure in R#2 has the highest H (12.63 GPa), whereas the E-r is related to the microstructure composition.