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Go to Editorial ManagerThis paper aims to investigate the effect of Ag nanoparticles addition in different percentages (0.12 wt. %, 0.15 wt. %, 0.25 wt. %, 0.35 wt. %) on the microstructure properties of Cu-21%Zn-6%Al shape memory alloy. Optical and SEM were carried out to studied such effects. Two heat treatments were carried out at (825 ℃ and 850 ℃) for 10 min and quenched in ice water. It was observed that both of heat treatment lead to formation M18R martensite with V-shape and needle like, but raising the temperature of heat treatment from 825 ℃ to 850 ℃ lead to a decrease formation α phase, which leads to improving the shape memory properties. Refinement of the grain size resulted as Ag nanoparticles addition increased from 0 to 0.25 wt. %, the grain size decreases from 1551 μm to 212 μm with reduction of 86.32 wt. % at 0.25 wt. % Ag. The microstructure observation indicated that the Ag nanoparticles addition leads to creating a multi-variant oriented martensite microstructure after quenching process in ice water.
Retained Austenite (RA) has great deal with the me- chanical properties of high strength low alloy steel. Therefore, in this paper, Retained Austenite volume fractions have been evaluated in AISI4340 alloy steel using two well-known meth- ods, X-Ray diffraction (XRD) and magnetic measurement methods. The specimens were heat treated using different heat- ing temperature and different cooling rate (different quenching media). A comparison between the results of two methods proved that there results were approximately Identical .The results show that Retained Austenite formation increase as heating (Austenizing ) temperature increase for the same quenching media ,as well as ,it increases by increasing cooling rate . The maximum amount of Retained Austenite found as (27.2 Wt %) which recognized when the specimens heated up to 1000˚C then quenched in Water while the minimum amount of Retained Austenite found as ( 7.06 wt%) when the specimens heated up to ( 800 ˚C) then quenched in Sand. Hardness tests using Vickers and Rockwell methods were used and the results show that hardness values decreased with increasing heating temperatures and the maximum Vickers micro-hardness and Rockwell hardness numbers were equal to (121.8HRB) and ( 516.35 HV) which were detected when heating up of the speci- mens were up to 800 ˚C then quenched in water. Tensile tests show that increasing cooling rate lead to increasing in Strength due to increasing of hardness which in turn, leads to increase in yielding points and ultimate strengths. Retained austenite effects on microstructure were investigated using scanning electron microscopy (SEM) and optical microscopy and the results show that at low cooling rate the microstructure consist of bainite and/or martensite phase with small amount of re- tained austenite, while, increasing heating temperature and cooling rate results in microstructure consist of martensite and retained austenite phases.
The mechanical properties of low alloy steel are significantly influenced by retained austenite (RA). Consequently, using the X-Ray diffraction (XRD) measurement method, the retained Austenite volume fractions in AISI4330 alloy steel have been assessed in this article. The specimens underwent heat treatment at various heating temperatures (800 ֯ C, 900 ֯ C,1000 ֯ C) and cooling rates (Water and Oil). The findings demonstrate that retained Austenite formation rises with rising heating (Austenitizing) temperatures for the same quenching media as well as with rising cooling rates. The specimens were heated to a temperature of 1000 °C and then quenched in water, yielding the highest amount of retained austenite (7.733 wt%), and the lowest amount (1.977 wt%), which was obtained when the specimens were heated to a temperature of 800 °C and quenched in oil. The Vickers method was employed to conduct micro-hardness testing, and the results demonstrate that hardness values are reduced as heating temperatures increase. Optical microscopy was used to investigate the effects of retained austenite on the microstructure. The results show that bainite and/or martensite phases with a small amount of retained austenite dominate the microstructure at low cooling rates, whereas martensite and retained austenite phases dominate the microstructure at higher heating and cooling rates.