Influence of Heat-Treatment on Microstructural and Mechanical Characteristic of Steel

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Ali Dad Chandio
Asif Ahmed Sheikh
Shahid Hussain Abro
Syed Bilal Hasan Rizvi
M. Shabbir Madad
M. Aftab Qureshi
Zulfiqar Ali
Hamza Suharwardi


The AISI 1045 steel is one of the structural steels widely used in the automotive sector for several key components such as connecting shafts, axles etc. It is also used in petrochemicals and power generation units. In material science and engineering, four interdependent parameters are of paramount importance: process, structure, properties and performance. Among all factors, the microstructure is of utmost importance since it governs the properties at large. For instance, the shape, size and distribution of micro-constituents play a vital role therein. Therefore, the main objective is to investigate the influence of thermal correlation on the material, such as annealing, normalizing, tempering and hardening. This was followed by the characterization utilizing Optical Emission Spectroscopy, Impact Testing and Rockwell Hardness Tester. In addition, the microstructure was also studied using the Optical Microscope with up to 1000x optical zoom. Results suggested an improved toughness and hardness when tempering temperature was reduced. This is attributed to decreased grain sizes of micro-constituents upon such treatment.

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