Atomic-scale analysis of early-stage precipitation in Ti(Al,Si)3 alloy

Publication date: 15 November 2017
Source:Materials & Design, Volume 134
Author(s): Tongtong Zhang, Guohua Fan, Hao Wu, Xiping Cui, Meng Huang, Kesong Miao, Lin Geng
The early-stage precipitation behavior of Si in Ti(Al,Si)3 alloy heated to 800°C and then down to room temperature (RT) is characterized at the atomic scale by in-situ transmission electron microscope (TEM). Three types of nanoparticles were observed in Ti(Al,Si)3 alloy during the early-stage precipitation, which contain Si-rich nanoclusters, Ti7Al5Si12 precipitates as well as Ti5Si3 precipitates. The precipitation sequence and orientation relationship (OR) for the early-stage precipitation in Ti(Al,Si)3 alloy are as follows: (i) small Si-rich nanoclusters firstly form in TiAl3 matrix due to the segregation of Si, coexisting with larger Si-rich nanoclusters; (ii) Si-rich nanoclusters that reach the critical size (20–30nm) serve as nucleation sites for metastable Ti7Al5Si12 precipitates with an OR: 002TiAl3//11¯6Ti7Al5Si12, 1¯10TiAl3//1151¯Ti7Al5Si12; and then (iii) the formation of Ti5Si3 precipitates is by transformation of metastable Ti7Al5Si12 with an OR: 101¯0Ti5Si3//001Ti7Al5Si12, 12¯13Ti5Si3//010Ti7Al5Si12.

Graphical abstract

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