Papers by Keyword: Squeeze Casting

Abstract: The microstructure of AZ91 (Mg-Al) alloy is comprised of α-Mg and β-Mg₁₇Al₁₂ massive phase. The lower melting point associated with the β-Mg₁₇Al₁₂ phase results in poor creep resistance of the alloy. In the present study, the AZ91 alloy with the addition of calcium (Ca, 1wt%) and cerium (Ce, 1wt%) is cast, and their effect on the microstructure and creep behavior of AZ91 alloy have been investigated. Thermally stable phases such as Al₂Ca and Al₁₁Ce₃ are introduced in the AZ91 alloy through the addition of Ca and Ce elements. Energy dispersive spectroscopy (EDS) and x-ray diffraction analysis confirmed the presence of these intermetallic phases in the microstructure. Tensile creep tests on the as-cast samples were performed at 175^°C temperature under 50 MPa stress. The study shows that the creep resistance of AZ91 alloy is greatly improved with the presence of Al₂Ca and Al₁₁Ce₃ intermetallic phases because of their better thermal stability than β-Mg₁₇Al_12.

Abstract: In this study, AZ91 alloy was used as the base material and calcium and cerium were added as alloying elements. Microstructural analysis through optical microscope (OM) and field emission scanning electron microscope (FESEM) revealed that AZ91 base alloy contains α-Mg matrix and β-Mg₁₇Al₁₂ interdendritic network. The inclusion of individual calcium and cerium resulted in a more homogeneous distribution of the interdendritic network in the AZ91-1wt.% Ca and AZ91-1wt.% Ce alloy. The secondary phase (Mg₁₇Al₁₂) was refined in the microstructure as a result of Ca and Ce addition where Ce addition forms a new rod-like phase that is recognized as Al₁₁Ce₃ and Ca addition forms a skeleton like structure of Mg₁₇Al₁₂ and Al₂Ca. Due to the formation of new Al₂Ca and Al₁₁Ce₃ intermetallics, the volume fraction of β-Mg₁₇Al₁₂ was more suppressed with Ca and Ce alloy additions. The grain size determined from Electron Backscatter Diffraction (EBSD) maps indicate the reduction in average grain size with individual Ca and Ce additions. The addition of these elements was found to improve the hardness of AZ91 alloy. Overall, the results of this study demonstrate the potential for using Calcium and Cerium as alloying elements in AZ91 alloy to improve its mechanical properties by modifying its microstructure.

Abstract: It is easy to occur solid-liquid separation during semi-solid rheological forming, which leads to poor uniformity of microstructure and properties and limits its application in high strength and toughness parts. In this paper, a semi-solid CuSn10P1 alloy slurry was prepared by an enclosed cooling slope channel (for short ECSC). The effect of ingate length on microstructure and properties by semi-solid squeeze casting was studied. The results showed that the proper increase of the length of the ingate is beneficial to improve the uniformity of the microstructure and properties of the semi-solid squeeze casting. The microstructure uniformity and properties are the best when the ingate length is 20mm. The ultimate tensile strength and elongation of semi-solid squeeze casting CuSn10P1 alloy with 20 mm ingate length reached 419.2 MPa and 13.4%.

Abstract: The evolution of the microstructure of A356.2 alloys prepared by the rheocasting and squeeze casting during solution heat treatment was investigated. In contrast with the conventional solution heat treatment process (3 hours at 540oC), a short time solution treatment process (less than 1 hour at 540oC) is applied in this paper. The results show that the rheocastings require a shorter solution time than the squeeze-castings to obtain spheroidized Si particles. After solution for 10 min, the X-ray diffraction inspection results show that the Mg₂Si phase completely is dissolved in both rheocastings and squeeze-castings. However, a small amount of Mg₂Si is found at the edge of the Si particle by scanning electron microscope observation. After solution for more than 20 min, the Mg₂Si phase is completely dissolved. Fe-rich phases, including AlSiFeMg and AlFeSi, exist throughout the solution process. The developed T6 heat treatment with a short solution time can effectively improve production efficiency and decrease process cost for the rheocasting process. Key words: A356.2 alloy, microstructure, short solution time, rheocasting, squeeze casting

Abstract: It is easy to form reverse segregation and shrinkage porosity defects during the solidification of CuSn10P1 alloy, which leads to the poor properties and limits its application in high strength and toughness parts. In this paper, semi-solid CuSn10P1 alloy slurry was prepared by enclosed cooling slope channel (for short ECSC). The effect of runner distance on microstructure and properties by liquid squeeze casting and semi-solid squeeze casting was studied. The results showed that the microstructure of semi-solid squeeze casting is finer than that of liquid squeeze casting, and the shrinkage defects are improved. The solid fraction with 65 mm runner is lower than that without runner in liquid squeeze casting and semi-solid squeeze casting due to the retention effect of solid phase in semi-solid slurry flow, but the properties with 65 mm runner is better than that without runner. The ultimate tensile strength, yield strength and elongation of semi-solid squeeze casting CuSn10P1 alloy with 65 mm runner distance reached 466.5 MPa, 273.6 MPa and 13.4%, which were improved by 26%, 19% and 97%, respectively, as compared to that of liquid squeeze casting.

Abstract: There is little datum related to microstructure and properties of Mg alloys squeeze-casted with pressure over 200 MPa. In this study, the microstructure and properties of Mg-6Zn-1.4Y (ZW61) alloy solidified under 100MPa to 800MPa were investigated. The results show that a remarkable microstructure refinement and porosity reduction can be reached through solidification under high pressure. The average grain size and the volume fraction of second phase, i.e. quasicrystal I-phase, decrease continuously with the increase of applied pressure. The tensile properties, especially elongation, are obvious enhanced because of the microstructure refinement and castings densification under high pressure. The ultimate tensile strength and elongation of ZW61 alloy in as-cast state are 243 MPa and 18.7% when the applied pressure is 800 MPa, which are increased by 35% and 118% respectively, compared with that of the gravity castings.

Abstract: Metal matrix composite has been developed to improve mechanical properties for the automotive component application. One crucial factor in achieving excellent mechanical properties is improving the properties of the aluminum matrix of composite by the heat treatment process. The mechanical properties of Al-Mg-Si matrix composites alloyed with Zn and reinforced with 5% SiC and 5%Gr particle were examined after the heat treatment process. The aluminum matrix is melted inside the crucible furnace at 850 °C and is added with SiC/Gr particle, followed by stirring at 7500 rpm to optimize the mixing of the composite. Then, the composite is poured into the preheated mold at 300 °C and then squeezed with 30 MPa of pressure. The heat treatment process consists of three steps; solution treatment, quenching, and artificial aging. The aging process is conducted with variation of temperature (140 °C, 180 °C and 200 °C) and holding time (2, 4, and 6 hours). The test results show that the mechanical properties of aluminum matrix composite tend to increase after the heat treatment process. The optimum mechanical properties are achieved at the aging temperature of 200 °C for 6 hours, with the hardness value of 60.3 HRA and the impact value of 0.112 Joule/mm².

Abstract: Aluminium alloys are having lightweight, high strength, good corrosive resistance, and toughness. In this paper, A7075/B4C/SiC Hybrid Composites fabricated with different wt. % of reinforcement materials by using stir and squeeze casting process. The SEM Microstructure have shown that uniform distribution of reinforcement particles in the A7075 matrix reinforced with 1 % wt. % B4C and 1 % wt. % SiC. The Mechanical properties of A7075/B4C/SiC Hybrid Composites were studied Composite A7075/B4C/SiC reinforced with 1 % wt. B4C and 1 % wt. SiC has shown more compressive and tensile strength compared to base alloy. The compressive strength of the composite increased 39.73 % and the tensile strength is increased 36.67 % compared to base alloy. From the dry sliding wear studies, the Composite with 1 B4C wt. % have shown less weight loss and coefficient of friction at all conditions due to the uniform distribution of the micro-particles within the matrix surfaces. Worn surface morphology has revealed that severe wear of A7075 base alloy became mild wear by preparing composite with 1 % wt. SiC, 0.5 wt. % B4C and then mild wear became less wear with shallow grooves by increasing reinforcement weight percentage of B4C from 0.5 to 1.

Abstract: An attempt has been made to investigate the microstructures and wear behavior of magnesium alloy AM100 (Mg-Al-Mn) based composites reinforced with 7 vol. % of ZrB₂, graphite or hybrid of (1:1) ZrB₂ and graphite particles as well as the unreinforced magnesium alloy. Magnesium alloy was melt under shield of inert gases and composites were prepared using stir casting method. Optical microscopy was used to study the microstructures of the unreinforced alloy and composites. The composites characterized primarily by the uniform distribution of particles in the matrix and a good adherence between the particles and matrix. XRD analysis was used to identify the phases of the unreinforced alloy and composites. The XRD diffraction pattern of AM100 matrix reveals different phases, namely, Mg, AlMn and Al₁₂Mg_17. Formation of these phases is due to the reaction between alloy constituents. Dry sliding wear tests were conducted by using a pin-on-ring apparatus. The wear rates of the composites and matrix alloy were measured at loads of 10, 20 and 30 N, and sliding speed of 0.7 m/s. The worn surfaces of the composite pins were examined by scanning electron microscopy (SEM). The experimental results of the wear tests showed that the magnesium based composites exhibited higher wear rate at all the applied loads when compared to those of the unreinforced magnesium alloy. The ZrB₂ reinforced magnesium composite exhibited the lowest wear rate amongst the composites material investigated in the present work.

Abstract: In the past, Mg-Zn alloys prepared by a two-step manufacturing process of casting plus extrusion have been demonstrated to be a good candidate for biodegradable applications. But, studies on fabricating of Mg-Zn alloys with a single step process of squeeze casting capable of producing porosity-free Mg alloys, which can reduce the cost, are limited. In the present work, Zinc (Zn) addition varying from 1.0 up to 10.0 wt. % was introduced into liquid magnesium. The alloyed liquid was squeeze cast under an applied pressure of 90 MPa. The results of mechanical testing on the squeeze cast Mg-Zn alloys shows that Zn is an effective additive for enhancing their mechanical properties, specifically, tensile and yield strengths at room temperature, but reducing the elongation. While the Zn addition rises from 1.0 to 10.0 wt.%, the ultimate tensile and yield strengths increases to 181.0 MPa and 105.0 MPa from 140.7 MPa and 39.3 MPa, while the elongation-to-failure (e_f) decreases to 3.7% from 6.2%, respectively. The reveal of the as-cast grain structure by an optical microscope (OM) indicates that the high Zn content reduces grain sizes considerably. The microstructures analyzed by a scanning electron microscope (SEM) with the energy dispersive spectroscopy (EDS) show that the secondary MgZn phase forms once Zn is introduced in sufficient amount. The grain refinement and the massive presence of the secondary MgZn phase at the boundaries of the refined grains should be responsible to the enhancement of the strengths and the reduction in the elongation. The developed pressurized casting without employing secondary manufacturing processes such as extrusion or heat treatment exhibits its advantages to enhance the mechanical properties of the Mg alloys with high Zn content over conventional fabrication processes, since high Zn-containing Mg alloys have a long freezing range and tend to form microshrinkage porosity.