# The Influence of Al Content on the Ignition and Flame Propagation Behavior of Ti1−xAlx Alloys in Enriched-Oxygen Environment

## TL;DR

This study shows that increasing aluminum content in titanium alloys affects their ignition and combustion behavior in oxygen-rich environments.

## Contribution

The paper identifies how Al content influences ignition temperature, oxygen pressure, and combustion rate through bonding energy, melting temperature, and heat release.

## Key findings

- The critical ignition temperature and oxygen pressure of Ti1−xAlx alloys increase with higher Al content.
- Combustion rate increases from 11.85 to 14.05 mm·s−1 as Al content rises from 20 at% to 70 at%.
- Higher Al content increases ignition activation energy from 105.44 to 153.04 kJ·mol−1.

## Abstract

What are the main findings?
The critical ignition temperature and oxygen pressure of Ti1−xAlx alloys increase as Al content increases from 20 at% to 70 at%.The combustion rate of Ti1−xAlx alloys increases from 11.85 ± 0.13 mm·s−1 to 14.05 ± 0.09 mm·s−1 as Al content increases from 20 at% to 70 at%.The influence of Al content on the ignition conditions and combustion rate is attributed to multiple factors involving bonding energy, melting temperature, and heat release.

The critical ignition temperature and oxygen pressure of Ti1−xAlx alloys increase as Al content increases from 20 at% to 70 at%.

The combustion rate of Ti1−xAlx alloys increases from 11.85 ± 0.13 mm·s−1 to 14.05 ± 0.09 mm·s−1 as Al content increases from 20 at% to 70 at%.

The influence of Al content on the ignition conditions and combustion rate is attributed to multiple factors involving bonding energy, melting temperature, and heat release.

What are the implications of the main findings?
A higher Al content increases the volume fraction of intermetallic phases, which improves the ignition conditions by strengthening the bonding character.A higher Al content accelerates the combustion kinetics by increasing the heat release during oxidation and reducing the melting temperature at the solid–liquid interface.These findings provide theoretical and data support for the safe use of intermetallic compounds and the design of new generation intermetallic compounds.

A higher Al content increases the volume fraction of intermetallic phases, which improves the ignition conditions by strengthening the bonding character.

A higher Al content accelerates the combustion kinetics by increasing the heat release during oxidation and reducing the melting temperature at the solid–liquid interface.

These findings provide theoretical and data support for the safe use of intermetallic compounds and the design of new generation intermetallic compounds.

Titanium aluminide intermetallics have gained considerable attention as high-temperature structural materials for aerospace applications, but are susceptible to “titanium fire” under extreme service conditions. The role of Al elements on the combustion behavior of titanium aluminide intermetallics remains not fully understood. Herein, the influence of Al content on the ignition critical condition and burning rate of Ti1−xAlx alloys was investigated by using promoted ignition combustion (PIC) tests under oxygen-enriched atmosphere. Results indicated that the critical oxygen pressure of Ti1−xAlx alloys increases from 0.11 MPa to 0.23 MPa, and the ignition temperature under oxygen pressure of 0.41 MPa increases from 1059.5 ± 4.8 K to 1120.4 ± 2.5 K as Al content increases from 20 at% to 70 at%. However, the combustion rate increases from 11.85 ± 0.13 mm·s−1 to 14.05 ± 0.09 mm·s−1 as Al content increases from 20 at% to 70 at%. Moreover, the activation energy for ignition increases from 105.44 kJ·mol−1 to 153.04 kJ·mol−1 as Al content increases from 20 at% to 70 at%. According to the microstructure analysis after combustion, the influence of Al content on the ignition activation energy and burning rate is attributed to multiple factors involving bonding energy, melting temperature, and heat release.