Ignition phenomena of bulk aluminum alloy as a function of oxygen pressure

An ignition phenomena of 6061 aluminum alloy was investigated as a function of oxygen pressure. Cylindrical aluminum alloy specimens were ignited in a pure oxygen environment by a focused CW CO2 laser beam. The experiments were conducted at oxygen pressures ranging from 0.084 to 2.413 MPa. The temperature history of the entire upper surface of the specimen and of a 0.5 mm diameter spot located initially at the center of the specimen top surface was recorded by using a commercial two-color ratio pyrometer and a fast-response, narrow-band, two-color pyrometer. Mass, brightness, and interior temperatures (for certain experiments) were also recorded throughout the experiment. The results show that the surface temperatures at ignition of the alloy obtained from the temperature curves are below the melting temperature of the aluminum oxide and are slightly dependent on oxygen pressure. The data indicate that the ignition mechanism is complex and probably composed of several phenomena acting both separately and in conjunction with each other.