Microstructure and Mechanical Properties Analysis of Quenched and Tempered AISI 4340 Steel
Abstract
This research was conducted to determine the optimum parameters in quenching and tempering processes of AISI 4340 steel. Quenching and tempering processes were carried out to modify the microstructure and mechanical properties, especially to achieve the high strength and toughness resilience for steel armor application. Steel is widely use as armor material due to its ease processing, lower production costs, high strength, good toughness, and heat treatment capabilities. This material has also a reasonable price and good availability. Metallurgical structure becomes a crucial factor, especially for ballistic-resistant vehicle applications. The samples of AISI 4340 commercial steel with dimension of 55x10x10 mm3 were austenized at temperature of 800 ∘C for 1 and 2 h in a muffle furnace and followed by quenching process with oil as the media. Furthermore, the quenched samples were then tempered at 300 ∘ C for 2, 3, and 4 h at the muffle furnace as well. Microstructure analysis was conducted by using optical microscopes. The result showed that quenching process promoted the phase transformation from the combination of ferrite and pearlite to be the ferrite and martensite with the shape like a needle. On the other hand, the tempering process promotes the transformation of martensite to bainite. Quenching has also led to increasing of hardness.
Keywords: AISI 4340, quenching, tempering, martensite.
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