What is the rate of change of the elastic modulus of the brake spring under extreme temperature conditions (-40℃ to 150℃)?

Under extreme temperature conditions, the change in the elastic modulus of the brake spring is affected by both material properties and temperature range. For carbon steel spring materials, the elastic modulus changes little in the low temperature section (-40℃ to 0℃). Experimental data show that in the range of -50℃ to 50℃, the elastic modulus fluctuation usually does not exceed 2%. After entering the high temperature section (60℃ to 150℃), the elastic modulus shows a nonlinear decay as the atomic spacing increases and the lattice thermal vibration intensifies. At 100℃, the elastic modulus of typical carbon steel materials decreases by about 3%-5%, while the decay rate of heat-resistant alloy materials such as nickel-based alloys can be controlled at 1%-3%. When the temperature approaches 150℃, the cumulative decrease in the elastic modulus of carbon steel can reach 8%-12%. If the material undergoes special heat treatment or adds alloying elements such as chromium and molybdenum, this value can be optimized to 5%-8%. It is worth noting that the rate of elastic modulus decay accelerates with increasing temperature, and the instantaneous rate of change at 150℃ may reach 0.1%/℃, which is mainly due to the lattice softening effect caused by the reduction of dislocation motion activation energy. For brake springs made of silicon-chromium alloy steel, their high-temperature stability is better than that of ordinary carbon steel, and the elastic modulus attenuation rate at 150°C can be controlled within the range of 6%-9%. This is due to the pinning effect of the stable carbide network formed by the alloy elements on the grain boundaries.