Aging and thermal expansion behavior of Si 3N 4p/2024Al composite fabricated by pressure infiltration method

Abstract

The aging and thermal expansion behaviors of Si 3N 4p/2024Al composite fabricated by pressure infiltration method were investigated. The peak-aging time and peak hardness both decrease with the increase of aging temperature for both the 2024Al alloy and Si 3N 4p/2024Al composite. The calculated activation energies of s′ (precursors of the Al 2MgCu) phase indicate that the precipitation of s′ phase in Si 3N 4p/2024Al composite occurs easily than in 2024Al alloy. The presence of Si 3N 4 particles does not alter precipitation sequence, but accelerates the process of aging precipitation in Si 3N 4p/2024Al composite. The experimental coefficient of thermal expansion (CTE) of Si 3N 4p/2024Al composite bellow 100°C is more close to the average value of the Kerner model (upper bound Schapery model) and lower bound Schapery model. Aging treated Si 3N 4p/2024Al composite presents the best dimensional stability due to low internal stress and strong pining effect on dislocations from fine dispersed precipitates (Al 2MgCu) and high density tangled dislocations. The good mechanical properties, compatible CTE with steel and high dimensional stability make Si 3N 4p/2024Al composite very competitive for application in the inertial guidance field.