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Go to Editorial ManagerExceptionally strong press-hardened steels (PHS) are significantly demanded in the automobile industry for satisfying the carbon neutrality criterion. Recent research attempts to produce advanced-ultrahigh-strength medium steels have resulted in a variety of alloying approaches, thermomechanical processing techniques, and microstructural modifications for these steel grades. It has been shown that adding microalloying components to standard Mn-B steels can refine the microstructure of PHS which leads to better mechanical properties such as hydrogen embrittlement resistance and other performance indicators for service. In this paper a general review about the effect of microstructure test on the mechanical behavior of Press Hardening Steel (PHS) where microstructure approaches have also demonstrated good potential for the mechanical characteristics of PHS steel, in line with need for new evaluation and discovery meantime, statistical data of the microstructural phases heavily influence the mechanical properties, microstructural image analysis is essential. The purpose of this paper is to know how the microstructure phases will effect on the strength and hardness of press hardening steel also the alloying elements adding impact on the microstructure formulation and mechanical features of PHS.
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.
Friction stir processing is a new method of changing the properties of a metal through intense, localized plastic deformation ,this process mixes the material without changing the phase (by melting or otherwise) and creates a microstructure with fine, equiaxedgrains, It is used to improve the microstructural properties of metals. In this paper, the enhancement of mechanical propertiesof friction stir welding specimens at variable rotation speeds (1100, 1300 and 1500 rpm) with constant feed speed (60mm/min) for 6061-T6 aluminum alloy is studied by using the friction stir processing method at the same variable rotation speed and feed speed in order to transform a heterogeneous microstructure to a more homogeneous, refined microstructure. The best results of the welding line at the parameter 60 mm/min weld speed and 1300RPM rotation speed for the friction stir welding (FSW) and friction stir processing (FSP) where the efficiency reaches to 84.61% for FSW and 89.05% for FSP of the ultimate tensile strength of the parent metal.
This 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.
The aim of this study is to investigate the effect of heat treatments on the impact properties of hot rolled high strength steel and describes the effect of tempering temperature and quenching media on the microstructure, hardness, and impact resistance of plates. In the present study a high strength steel was austenitized at 900 °C with different quenching medium and followed by tempering at 300 °C, 500 °C. After thermal treatments, the values of Charpy impact resistance, hardness, and microscopic structure were evaluated from mechanical and metallographic analysis of metals respectively. The change of mechanical properties and microstructure of the metal with the existence of heat treatment with the ballistic performance of high-strength steel. Experimental results showed that tempering at 500 °C for 2 hours after water quenching medium it provides the best mechanical properties in conjunct on with an improved in microstructure.
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 present study aims to investigate the influence of heat treatment and surface finish on the behavior of crevice corrosion resistance of AISI 410 and 416 martensitic stainless steels thus, to quantify the conditions at which crevice corrosion minimize as possible. The experimental work carried out during this study involves material selection, chemical composition tests, specimens preparation before heat treatments, austenitizing at temperature range (925-1010˚C) and for holding time periods of (30, 45 and 90 min), air and oil quenching followed by tempering at heating range of (205- 605 ̊C) and for 45 min, micro hardness tests, specimens grinding, surface roughness measurements, crevice corrosion tests, crevice evaluation and microstructure tests. Theoretically, empirical equations for crevice maximum depth under the effect of surface roughness and hardness for both AISI 410 and 416 steels were determined. While for microstructure analysis, carbides average area was determined by using the ImageJ analysis program and a mathematical model was also predicted. Results showed that, as hardness and surface roughness increase crevice corrosion resistance decreases. Therefore, material treated by annealing can minimize crevice corrosion rates more than that treated with hardening.
In this study the powder metallurgy technique was used to prepare the composite materials using the aluminum powder as the basis metal, with the additions of the 2, 4 and 6%Wt. of ZrO2-Cu coating and mixing it manually for 15 minutes at (30-32 oC). Then the mixture are compacted at pressure 320 MPa and sintering at 640oC in the atmosphere furnace with argon gas protection. The physical properties include the green density, sintering density, porosity, and microstructure were examined for the prepared samples. X-ray analyzer was used to identify the phases changes in order to find the chemical reaction which it can be excepted occurred in the sintering samples. The result of X-Ray diffraction shows that there is new phase exist after sintering for all weight percentage.
Image segmentation is the process of automatically dividing an image into distinct, meaningful, and non-overlapping regions. The quality of the segmentation process determines the efficiency of other image processing tasks. Analyzing microstructural images is crucial since the mechanical properties are strongly dependent on the microstructural phases’ statistics. These images are considered one of the most difficult and challenging images to deal with due to their special characteristics, such as the convergence in pixels intensity values, overlapping in colors, boundaries and textures in phase regions, infinite shapes of grains and colonies, etc. As there is no generic technique suitable to be used with all microstructures, this work reviews techniques that have been effectively used and recommended to be employed in metallurgical research, with a brief description of their principles, advantages, and disadvantages, and discusses their applicability. The major aim of this work is to spare time and effort searching for and experimenting with all the available methods for future researchers.
Single roll melt spinning is a non-conventional forming process used to produce rapidly solidified thin ribbons as a near net shaper by direct casting from liquid state. In this paper, single roll made from brass with a diameter of 150 mm was used to produce rapidly solidified Al-Mg alloys ribbons. The ribbons are produced with thickness in the range of 20 to 330 µm. The results exhibited unique advantages in refining the microstructure, and modifying the mechanical properties of these ribbons. The hardness was improved to about twice the original hardness of alloy. Moreover, corrosion resistance of alloy was improved and their rate was redcued from 10.02 to 1.643 mpy for alloy type 5052 and from 6.91 to 1.943 mpy for 5083.
Failures in the steam tubes of boiler furnaces in Najebia power plant was studied experimentally. Visual examination, mechanical tests, microscopic test and chemical analyses were performed. Visual examination showed the types of failure in the tubes. Tensile and hardness tests were performed to estimate the variation in the mechanical properties of the tubes metal and compared with the new tubes. Microscopic test for the failed tubes used to recognize the difference in the microstructure to the metal of the tubes. Chemical analyses involved chemical composition of the tubes metal, river and feed water analyses, water treatment, fuel analyses and analysis of deposits and oxides on the external and internal sides. Overheating and wall thinning of the tubes resulted from oxygen escaping to the inner side of these tubes, and presence of deposits and oxides on the external and internal sides which led to failure was studied extensively. Engineering remedies were also given to confine the problem and to prevent it in future.
The objective of this research is to characterize new technique of copper filler addition to the brazing joints of 316L stainless steel to overcome the wetting problem between them. This technique includes the electrochemical deposition of copper on the stainless steel joint parts to insure optimum coinciding, minimum oxidation during brazing heating, and consequently good wetting and bonding. An evaluation of the present technique and a comparison with traditional one were performed. The samples ware tested to find the shear strength, microhardness, microstructure and x-ray diffractometry. In general, the present new electrodeposited fillers were clearly better than the traditional filler in producing perfect joints with higher shear strength. On the other hand, there was an opportunity of production acceptable joints with electrodeposited fillers under air environment.