Porosity study and effects on mechanical properties of discontinuous reinforced metal matrix composite (DRMMC)

The effects of porosity on mechanical properties of cast discontinuous reinforced meta] matrix composite (DRMMC) were investigated. Hence, a casting rig was fabricated to produce DRMMCs via conventional and modified stir casting method . The modified stir casting method performed pre-heating of reinforcement particles during matrix alloy melting. Silicon carbide particle reinforced aluminium alloy composites were produced with three different stirring speeds: 100, 200 and 500rpm. Cast DRMMCs were evaluated in as-cast condition for microstructure analysis, porosity and density measurement and mechanical testing. The mechanical properties of cast DRMMC were determined from tensile and fatigue tests conducted at room temperature. Tensile tests were referred to ASTM B557 standard while the axial fatigue test (ASTM E466) was conducted at stress ratio (R) of -1. A finite element method (FEM) analysis was carried out using Solidworks 2003 software. It was found that the major causes of porosity occurrence in cast DRMMC were clustered silicon carbide particles, gas entrapment and solidification shrinkage. From porosity measurement, conventionally stir cast DRMMCs contained higher porosity compared to the modified stir cast DRMMCs. The least content of porosity evaluated is at 0.09% in modified stir cast DRMMC, while the highest is at 12.45% in conventionally stir cast DRMMC. Fatigue strength (at 1 x 107 cycles) of cast DRMMCs at 5, 10, and 15% reinforcing SiC particle were 129.7, 141.5 and 157.3 MPa respectively. Based on the FEM analysis, porosity in conventionally stir cast DRMMC promotes higher von Mises stress as much as 40.2 MPa compared to 12.6 MPa in modified stir cast DRMMC. The porosity contents increased with increasing silicon carbide particles. Higher stirring speed tended to entrap more gas during mixing, whereas a lower stirring speed was ineffective to disperse SiC particles and results in clustering. Increasing porosity content in cast DRMMC had decreased the density and tensile properties ofDRMMC as depicted by the FEM analysis. Though, fatigue strength increased as a result of existing constraints in form of porosity

Proposity study and effects on mechanical properties of discontinuous reinforced metal matrix composite (DRMMC)

The effects of porosity on mechanical properties of cast discontinuous reinforced meta] matrix composite (DRMMC) were investigated. Hence, a casting rig was fabricated to produce DRMMCs via conventional and modified stir casting method . The modified stir casting method performed pre-heating of reinforcement particles during matrix alloy melting. Silicon carbide particle reinforced aluminium alloy composites were produced with three different stirring speeds: 100, 200 and 500rpm. Cast DRMMCs were evaluated in as-cast condition for microstructure analysis, porosity and density measurement and mechanical testing. The mechanical properties of cast DRMMC were determined from tensile and fatigue tests conducted at room temperature. Tensile tests were referred to ASTM B557 standard while the axial fatigue test (ASTM E466) was conducted at stress ratio (R) of -1. A finite element method (FEM) analysis was carried out using Solidworks 2003 software. It was found that the major causes of porosity occurrence in cast DRMMC were clustered silicon carbide particles, gas entrapment and solidification shrinkage. From porosity measurement, conventionally stir cast DRMMCs contained higher porosity compared to the modified stir cast DRMMCs. The least content of porosity evaluated is at 0.09% in modified stir cast DRMMC, while the highest is at 12.45% in conventionally stir cast DRMMC. Fatigue strength (at 1 x 107 cycles) of cast DRMMCs at 5, 10, and 15% reinforcing SiC particle were 129.7, 141.5 and 157.3 MPa respectively. Based on the FEM analysis, porosity in conventionally stir cast DRMMC promotes higher von Mises stress as much as 40.2 MPa compared to 12.6 MPa in modified stir cast DRMMC. The porosity contents increased with increasing silicon carbide particles. Higher stirring speed tended to entrap more gas during mixing, whereas a lower stirring speed was ineffective to disperse SiC particles and results in clustering. Increasing porosity content in cast DRMMC had decreased the density and tensile properties ofDRMMC as depicted by the FEM analysis. Though, fatigue strength increased as a result of existing constraints in form of porosit

Fiber Laser Welding of Dissimilar 2205/304 Stainless Steel Plates

In this study, an attempt on pulsed-fiber laser welding on an austenitic-duplex stainless steel butt joint configuration was investigated. The influence of various welding parameters, such as beam diameter, peak power, pulse repetition rate, and pulse width on the weld beads geometry was studied by checking the width and depth of the welds after each round of welding parameters combination. The weld bead dimensions and microstructural progression of the weld joints were observed microscopically. Finally, the full penetration specimens were subjected to tensile tests, which were coupled with the analysis of the fracture surfaces. From the results, combination of the selected weld parameters resulted in robust weldments with similar features to those of duplex and austenitic weld metals. The weld depth and width were found to increase proportionally to the laser power. Furthermore, the weld bead geometry was found to be positively affected by the pulse width. Microstructural studies revealed the presence of dendritic and fine grain structures within the weld zone at low peak power, while ferritic microstructures were found on the sides of the weld metal near the SS 304 and austenitic-ferritic microstructure beside the duplex 2205 boundary. Regarding the micro-hardness tests, there was an improvement when compared to the hardness of duplex and austenitic stainless steels base metals. Additionally, the tensile strength of the fiber laser welded joints was found to be higher when compared to the tensile strength of the base metals (duplex and austenitic) in all of the joints

Thermally-Induced Crack Evaluation in H13 Tool Steel

This study reported the effect of thermal wear on cylindrical tool steel (AISI H13) under aluminum die-casting conditions. The AISIH13 steels were immersed in the molten aluminum alloy at 700 °C before water-quenching at room temperature. The process involved an alternating heating and cooling of each sample for a period of 24 s. The design of the immersion test apparatus stylistically simulated aluminum alloy dies casting conditions. The testing phase was performed at 1850, 3000, and 5000 cycles. The samples were subjected to visual inspection after each phase of testing, before being examined for metallographic studies, surface crack measurement, and hardness characteristics. Furthermore, the samples were segmented and examined under optical and Scanning Electron Microscopy (SEM). The areas around the crack zones were additionally examined under Energy Dispersive X-ray Spectroscopy (EDXS). The crack’s maximum length and Vickers hardness profiles were obtained; and from the metallographic study, an increase in the number of cycles during the testing phase resulted in an increase in the surface crack formation; suggesting an increase in the thermal stress at higher cycle numbers. The crack length of Region I (spherically shaped) was about 47 to 127 µm, with a high oxygen content that was analyzed within 140 µm from the surface of the sample. At 700 °C, there is a formation of aluminum oxides, which was in contact with the surface of the H13 sample. These stresses propagate the thermal wear crack length into the tool material of spherically shaped Region I and cylindrically shape Region II, while hardness parameters presented a different observation. The crack length of Region I was about 32% higher than the crack length of Region II

Study of an optimal surface property of carbide cutting tool by surface modification method

This thesis introduces the effect of textures on carbide insert rake surface to the surface roughness on using laser surface texturing. Surface texturing is one of the techniques for enhancing tribological properties of mechanical components. This is also widely used which contributes a lot in numerous engineering applications. Various parameters of pattern have been used to improve tribological performance. Parallel grooves has been used because able to trap wear debris, change stress distribution and low surface roughness. The fabrication of textures on carbide insert surface is one of the predominant methods to enhance the sustainability of laser process with cemented carbide insert. Laser process was utilized using CK-FB3D 3-Axis Control fiber laser marker to fabricate textures that were effective use to cut the tool. Olympus BX51M metallurgical microscope was using to check condition of the rake surface carbide insert. After that, depth of cut of the laser on the carbide insert was investigate using video measuring system. Furthermore, the surface roughness was utilized using surface roughness tester. Carbide insert has been tested using four parameters and found that relatively low scanning speed and frequency resulted in less surface roughness for textured carbide insert. Low surface roughness was discovered because high hardness of the carbide insert would make the less friction when cutting the tool

Superhydrophobic zinc oxide/epoxy coating prepared by a one-step approach for corrosion protection of carbon steel

Corrosion in carbon steel (CS) has been an existing issue and it calls attention to the need for improved corrosion protection. At present, superhydrophobic (SHB) coating technology has piqued the interest of researchers as alternative means of mitigating metal corrosion. Herein, a one-step solution deposition process was used to prepare an SHB coating based on nano-zinc oxide/epoxy (ZnO/EP) on CS and its corrosion resistance performance was analyzed by the means of electrochemical analysis and compared with that of the blank CS metal and the regular coatings (plain EP and regular ZnO/EP). Results implied the as-prepared SHB coating shows remarkable improvement in corrosion protection for the substrate. Notably, it exhibited higher in both impedance modulus (|Z|) and coating resistance (Rc) results approaching 1010 Ωcm2, than those of regular coatings by 3 orders of magnitude to that of plain EP (∼107 Ω cm2), and 1 order of magnitude to regular coating (∼109 Ω cm2), indicating its superior corrosion resistance performance. Besides that, the superior inhibitive effect of the SHB ZnO/EP (ZES) is also proven by the potentiodynamic polarization (PDP) results, in which the Icorr value is suppressed down to 2.08 × 10−11 A/cm2, thereby achieving an excellent corrosion rate result of 3.38 × 10−11 mm/year. The exceptional barrier protection is ascribed to the presence of a stabilized air interlayer captured within the coating/electrolyte interface thus effectively blocking the penetration of electrolyte into the coating. This facile yet effective one-step processed SHB coating offers an effective route to improve the corrosion resistance performance of the CS metal and thereafter expand its potential applications

Development of laser cutting and engraving machine utilising PC-NC controller

Laser machining is one of the most popular applications of the laser material processing. New processes such as laser cutting and laser engraving have been evolved ever since laser machining became popular in the manufacturing industries over the past decades. Therefore, this study developed the laser cutting and engraving machine by utilizing PC-NC controller. The controlling system that has been developed is capable of executing a stored program correctly and moving the laser smoothly in the desired way. Hence, the PC-NC controller specifically tailored for laser cutting and engraving which can control all the relevant parameters in real time except the laser beam power. So the moving table which attached to the laser head can run smoothly and control the crucial parameters accurately. The laser machine then is tested with different types of work piece to investigate the effectiveness of cutting and engraving processes using this system. In general, the laser system for cutting and engraving utilizing PC-NC controller successfully developed