TY - JOUR ID - TI - Effect of Retained Austenite on the Micro-structure and Mechanical Properties of AI-SI4340 High Strength Low Alloy Steel (HSLA steel) Using Magnetic Saturation Measurement and X-Ray Diffraction methods AU - Nagham. M Abdulkareem نغم عبدالكريم AU - Murtadha A. Jabbar مرتضى جبار PY - 2017 VL - 17 IS - 2 SP - 1 EP - 8 JO - Basrah Journal for Engineering Sciences مجلة البصرة للعلوم الهندسية SN - 18146120 23118385 AB - Retained Austenite (RA) has great deal with the mechanical properties of high strength low alloy steel. Therefore,in this paper, Retained Austenite volume fractions have beenevaluated in AISI4340 alloy steel using two well-known methods, X-Ray diffraction (XRD) and magnetic measurementmethods. The specimens were heat treated using different heating temperature and different cooling rate (different quenchingmedia). A comparison between the results of two methodsproved that there results were approximately Identical .Theresults show that Retained Austenite formation increase asheating (Austenizing ) temperature increase for the samequenching media ,as well as ,it increases by increasing coolingrate . The maximum amount of Retained Austenite found as(27.2 Wt %) which recognized when the specimens heated upto 1000˚C then quenched in Water while the minimum amountof Retained Austenite found as ( 7.06 wt%) when the specimensheated up to ( 800 ˚C) then quenched in Sand. Hardness testsusing Vickers and Rockwell methods were used and the resultsshow that hardness values decreased with increasing heatingtemperatures and the maximum Vickers micro-hardness andRockwell hardness numbers were equal to (121.8HRB) and (516.35 HV) which were detected when heating up of the specimens were up to 800 ˚C then quenched in water. Tensile testsshow that increasing cooling rate lead to increasing in Strengthdue to increasing of hardness which in turn, leads to increasein yielding points and ultimate strengths. Retained austeniteeffects on microstructure were investigated using scanningelectron microscopy (SEM) and optical microscopy and theresults show that at low cooling rate the microstructure consistof bainite and/or martensite phase with small amount of retained austenite, while, increasing heating temperature andcooling rate results in microstructure consist of martensite andretained austenite phases.

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