International Journal of Engineering and Information Systems (IJEAIS)   Year: 2019 | Volume: 3 | Issue: 7 | Page No.: 41-46 Influence of Heat Treatment Temperature on the Strain Hardening Exponent and Strength Coefficient of AISI 4140 Alloy Steel Meshref A. A., Mazen A. A., El-Giushi M. A. and Ashraf T.M. Abstract: This study aims to discuss the effect of stress relief and full annealing temperatures on the strain hardening exponent and strength coefficient of AISI 4140 alloy steel. The material used is ultrahigh strength low alloy steel (AISI 4140 alloy steel). Two types of heat treatments were applied in this study. The first type was stress relief annealing, the second was full annealing. Effect of stress relief at temperature (500, 600 and 660 0C) on the strain hardening exponent and strength coefficient of AISI 4140 alloy steel was analyzed. It was found that the strain hardening exponent increased with increasing stress relief temperature, whereas the strength coefficient first increased and then decreased with increasing stress relief temperature. Also influence of full annealing at temperature (800, 860 and 900 0C) on the strain hardening exponent and strength coefficient of AISI 4140 alloy steel was analyzed. It was found that strain hardening exponent increased upon full annealing up to 8600C, and then decreased as the full annealing temperature was increased. In contrast, the strength coefficient of AISI 4140 alloy steel decreased upon full annealing up to 8600C, and then increased with increase in full annealing temperature.