Atomic-scale analysis of early-stage precipitation in Ti(Al,Si)_3 alloy

摘要

The early-stage precipitation behavior of Si in Ti(Al,Si)(3) alloy heated to 800 degrees 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:(002)(TiAl3)//(1 (1) over bar6)(Ti7Al5Si12), [(1) over bar 10](TiAl3) //[115 (1) over bar](Ti7Al5Si12); and then (iii) the formation of Ti5Si3 precipitates is by transformation of metastable Ti7Al5Si12 with an OR: (10 (1) over bar0)(Ti5Si3)//(001)(Ti7Al5Si12), [1 (2) over bar 13](Ti5Si3) //[010](Ti7Al5Si12). (C) 2017 Elsevier Ltd. All rights reserved.