Effect of copper addition on grain refinement of austenite in Fe-8wt.%Ni-(0.3)Wt.% Cu alloy

The effect of copper addition on martensitic structure and reversion from martensite to austenite behaviours upon heating were investigated to clarify mechanism of grain refinement of austenite in Fe-8wt.%Ni-Cu alloys. Upon water-quenching, the alloys underwent a martensitic transformation that exhibited a typical lath-martensitic structure. It was found that prior-austenite grain and martensite-packet sizes were refined with increasing copper content. The grain refinement was not due to a decrease of grain growth rate of the austenite. However, it was found that nucleation rate of the austenite on reversion was increased by the copper addition. In Fe-8wt.%Ni alloy heated in (austenite+ferrite) region, reversed austenite grains were formed at high angle boundaries such as prior austenite grain boundary and packet boundary. On the other hand, TEM observation of the Fe-8wt.%Ni-3wt.%Cu alloy revealed that fine copper particles precipitated within the martensitic structure and the reversed austenite grains also formed within lath-structures and lath boundary. It means that the copper addition promoted formation of the reversed austenite within martensitic matrix and resulted in the grain refinement of the prior-austenite in Fe-8wt.%Ni-Cu alloy

The effects of mg addition on the microstructure and mechanical properties of Thixoformed Al-5%Si-Cu alloys

In this study, the effects of different amounts of magnesium (Mg) on the microstructures and tensile properties of thixoformed Al–5%Si–Cu alloys were investigated. Three different alloys containing various amounts of Mg (0.5, 0.8 and 1.2 wt%) were prepared through the cooling slope casting technique, before they were thixoformed using a compression press. Several of the thixoformed samples were then treated with a T6 heat treatment, that is, solution treatment at 525 C for 8 h, quenching in warm water at 60 C, followed by aging at 155 C for 4 h. All of the samples were then characterised by optical microscopy (OM), scanning electron microscopy (SEM) energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as by tensile tests. The results revealed that magnesium was able to refine the size of a-Al globules and the eutectic silicon in the samples. It was also observed that a compact p-Al9FeMg3Si5 phase was formed when the magnesium content was 0.8 wt% and 1.2 wt%. The mechanical properties of the thixoformed alloys improved significantly after the T6 heat treatment. The highest attainment was recorded by the latter alloy (i.e. with 1.2 wt%Mg) with its ultimate tensile strength (UTS) as high as 306 MPa, yield strength (YS), 264 MPa, and elongation to fracture of 1.8%. The fracture of thixoformed alloy with a low Mg content (0.5 wt%) showed a combination of dimple and cleavage fracture, whereas in the alloy that contained the highest Mg content (1.2 wt%), cleavage fracture was observed

Influence of iron on phase stability and corrosion resistance of Ti-15%Cr alloy

In this study, the effect of Fe addition on the phase stability and corrosion resistance of Ti-15%Cr alloys was investigated. The alloying phenomenon in the specimens was also investigated to determine the effectiveness of the application of pure metallic powders as raw materials for the powder metallurgy method. Ti-15%Cr-1%Fe alloys exhibited needle-like structures within equiaxed structures, while Ti-15%Cr-5%Fe and Ti-15%Cr-10%Fe alloys only showed equiaxed grains. XRD results showed that the β phase could be stabilized by the addition of 5% or more Fe to the alloy. Although the pure powders were used as raw materials, the designated chemical composition, i.e. Ti-15%Cr-(1~10)%Fe can be achieved during sintering. The alloying phenomenon occurred upon sintering due to the high diffusivity of Cr and Fe within the β Ti matrix. The corrosion resistance of the newly developed Ti-15%Cr alloys was significantly improved compared with a commercial Ti-6%Al-4%V alloy

Peran BAZNAS Sumatera Selatan dalam Menghadapi Dampak Pandemi COVID-19 di Kota Palembang

Penelitian ini bertujuan untuk mendeskripsikan peran BAZNAS Sumatera Selatan dalam menghadapi dampak pandemi Covid-19 di Kota Palembang. Metode yang digunakan dalam penelitian ini adalah kualitatif deskriptif. Penelitian ini menemukan bahwa BAZNAS Provinsi Sumatera Selatan telah melaksanakan pendistribusian dana zakat untuk membantu menanggulangi dampak Pandemi COVID-19. Meskipun dalam pelaksanaannya masih terhambat oleh prasarana yang kurang mendukung. Dalam pelaksanaannya, BAZNAS membagi menjadi dua jenis distribusi, yaitu konsumtif dan produktif

Effect of one-year corrosion on steel bridge materials in the maintenance stage with the Charpy impact test method

Corrosion of steel bridges is a major problem because it has the potential to reduce the performance of the structure over its lifetime. One factor that should not be reduced is fracture toughness, so this should be a very important concern in the maintenance program. Existing guidelines do not specify when corrosion conditions are hazardous and when corrosion conditions are not hazardous to structural performance. This study aims to explain how long corrosion does not cause danger, and when corrosion becomes dangerous. The Charpy Impact Test was used in this study to examine the effect of corrosion with a corrosion duration of weekly up to one year on fracture toughness. The series of tests in this research program used SM-490-type specimens which are steel plates commonly used for bridge structures. Specimens with variations in corrosion duration which were the result of immersion in sulfuric acid solution to simulate corrosion growth were then subjected to crack toughness testing. The toughness of each specimen was tested with a corrosion period starting from 1 week and so on up to 1 year to determine the level of fracture toughness. The results obtained from all tests showed that there was no decrease in the toughness of the corroded specimens for up to 1 year. The data presented in this study is very helpful for the designers and maintainers to plan corrosion treatment programs with clearer and more accurate considerations in assessing the structural integrity of steel bridges affected by corrosion

An overview of semisolid processing of aluminium alloys

Semisolid metal processing (SSM) or thixoforming is a new technology that offers several advantages over liquid processing and solid processing. This process utilizes semisolid behavior as well as reduces macrosegregation, porosity, and forming forces during shaping process. A lot of research work has been carried out by various researchers in order to exploit the potential of this process to produce different products especially for automotive industry. This paper will summarise the rheological behavior of aluminium alloys in semisolid slurries, thixoformability of modified aluminium alloys, the effect of feedstock production method on mechanical properties, and the importance of developing low-cost raw materials for semisolid processing

STRESS RELAXATION BEHAVIOUR AND MECHANISM OF HEAT TREATED INCONEL 718 IN HIGH TEMPERATURE ENVIRONMENTS

The stress relaxation behaviour of heat treated nickel-base superalloy Inconel 718 at high temperature was investigated. Solution treatment was applied on the as-received material at 980 oC for 1 hour before water quenching followed by double aging treatments at 720 oC for 8 hours and 621 oC for 8 hours, then cooled in air. The stress relaxation test was conducted at 1 % strain at different test temperatures of 550 oC, 650 oC and 750 oC. The tests were carried out for a total of 72 hours. The tests were interrupted at 3 hours and 48 hours to investigate the evolution of microstructure and changes in material properties by using Scanning Electron Microscope (SEM) and X-Ray Diffractometer (XRD). The results showed that thermal dependent stress increased with decreasing temperature. In contrast, stress relaxation rate increased with increasing temperature. Microstructure observation by SEM showed that recovery process occurred. This was further supported by the decrease in dislocation density with increase in time and temperature, which is in-line with the Vickers micro-hardness results

TRIZ approach for machining process innovation in cryogenic environment

This paper presents the utilisation of TRIZ approach in machining process of AISI 4340 in cryogenic environment which lead to product improvement in turning process. The machining study is carried out in two stages; FEM simulation for finding the optimum condition and machining experiment to visualise the product improvement that involved plastic deformation. The simulation result revealed that at moderate to high cutting speed, high feed rate and high depth of cut will result in high temperature that enable for the change in phase of AISI 4340 from retained austenite to fully martensite. A sample from machining experiment at optimum cutting condition found that the microstructure changes beneath the machined until at the depth of ∼7 μm with high hardness to 8,500 N/mm2 Martens hardness at the machined surface. This hardness is equivalent to the hardness obtained in conventional case hardening process that is required after the machining of AISI 4340 in their application as automotive engine parts in order to enhance these parts in their service lives. This study reveals that the TRIZ approach helps to systematically analyse the various outcomes in this study started with process limitation, problem identification, axiomatic and Su-field analysis