Coefficient of Thermal Expansion

The coefficient of thermal expansion was determined for a series of PM materials in accordance with ASTM E228. A push-rod dilatometer was used for these tests, using a 3.6 °F (2.0 °C)/minute heating rate in a nitrogen atmosphere. The mean CTE was determined from room temperature up to a series of temperatures. Both as-sintered and heat-treated materials were evaluated. The heat-treated steel alloys had been tempered at 350 °F (180 °C) prior to the CTE test. The CTE response is dependent upon the tempering temperature, i.e. this low temperature tempering cycle allows for a contraction in the heat-treated steel over the temperature range of 600-700 °F (315-370 °C). Once heated through this temperature range this contraction will not recur in subsequent heating cycles. PM aluminum materials were tested in the T2 and T8 conditions.