Papers by Keyword: Al-Cu Alloy

Abstract: Aluminium-copper alloys are known for their very good strength at high temperature .Addition of copper improves the strength at high temperatures due to precipitation strengthening. Fluidity in casting is the major factor which affects the cast quality of the final components. Addition of Silicon with copper in Aluminium improves fluidity and finally quality of the cast components. But presence of Silicon adversely affects the strength at high temperature. In the present work cooling curve analysis of Al-Cu alloy (without Silicon) is done for different wt% of copper addition. The current study for Al-Cu alloy is based on sand casting method as it is one of the cost effective manufacturing method. Cooling curve obtained from the simulation results used to predict the fluidity, microstructure of the alloy when copper wt% is varied. Predicted microstructure and grain structure from the cooling curve goes well with the microstructure studied from shop floor casting .In the present work “Z-cast” casting simulation software is used for casting simulation. Among three different alloy composition studied aluminium with 8% copper gives the best results when compared on the basis of grain size .But fluidity analysis reveal poor fluidity for the alloy having 8 wt% of copper. The current analysis helps to study the optimum aluminium –copper alloy composition that can be used in high temperature applications.

Abstract: The effect of overheating of the melt and cooling rate of alloys of the Al-Cu system with a copper content of 25.0 – 36.0% ( mass.), the rest of the aluminum is investigated. It is shown that an overheating of the liquid at 50 – 100 K above the liquid-liquid line leads to the formation of a fine-dispersed eutectic structure and the inhibition of the formation of primary aluminum crystals in the pre-evacuation of alloys and the Al₂Cu phase in hypereuvtectic alloys, in accordance. An increase in the melt overheating temperature by 150 K above the liquid-liquid line and the subsequent cooling at 10³ – 10⁴ K/s leads to the complete inhibition of the formation of primary crystals. An overheating of the melt on 100 – 150 K alloys above the liquid line and subsequent cooling with a velocity of 10³ – 10⁴ K /s reduces the rate of corrosion by 30 – 45% and increases the numerical value in 1.3 – 1.45 times the relative wear resistance, and the brittleness of alloys decreases in 1.2 – 1.35 times in comparison with the samples after casting.

Abstract: In this study, the effect of the surface structure and hydrogen on the fatigue strength of electroless Ni-P plated Al-2%Cu alloy was investigated. As the results, the following points were clarified. Large precipitates were recognized near the specimen surface of the furnace-cooled Al-Cu alloy, but these were not recognized in the aged Al-Cu alloy. Fatigue strength of the Al-Cu alloy specimen subjected to Ni-P plating after a furnace cooling treatment was overall reduced rather than one of the non-processed specimens. Fatigue strength of the Al-Cu alloy specimen subjected to Ni-P plating after the aging treatment showed a clear increase in comparison to one of non-processed materials. In the Al-2%Cu alloy specimens subjected to Ni-P plating after the furnace cooling treatment or aging treatment, a clear hydrogen desorption was recognized. On the other hand, there was only hydrogen desorption from a few of the non-processed specimens. It is considered that the poor fatigue strength of the plating materials is mainly due to the interaction between the surface precipitates and hydrogen gas.

Abstract: In this experiment, the influence of non-treated (NT), natural aging (T4) and artificial aging (T6) heat-treatments was investigated on the tensile strength of Al-5.9Cu-1.9Mg at different casting temperatures. Three levels of casting temperatures were used: 688, 738, 788 °C while the mold temperature was kept constant at 220 °C. The cast sample was heat-treated by natural aging and artificial aging techniques. The results show that the tensile strength in the non-treated sample decreases initially and then rises slightly with increasing casting temperature. The effect of casting temperature on T4 involved first an increase in tensile strength and then a decrease when elevating the casting temperature, but with no significant effect. In the T6 treatment, the tensile strength first decreases followed by a slight increase with increasing casting temperature. The heat treatment process improved the tensile strength in the three different samples, except at a casting temperature of 768 °C.

Abstract: Complex dendritic structures can be simulated directly by phase field method. However, phase field method needs a very fine mesh computing and memory requirements. A new calculation method named zone partitioning sequential calculation method is proposed to expand the simulation area of phase field method. The simulation area can be divided into several parts, and the parts can be calculated one by one in a certain order by the new method. This new method can reduce the computing and memory requirements of single calculation, because a part of the simulation area is less than the whole simulation area. Although this method could make error in the interface of different parts of the simulation area when the grains go through the interface, but the error has less effect on the grain growth. By using phase field method, coupled with zone partitioning sequential calculation method, the simulation of the directional solidification process of Al-Cu binary alloy is operated. The results show that the new method can be applied to phase field simulation of binary alloy solidification in a large area. The simulation results have certain accuracy and reliability.

Abstract: The additive manufacturing of metallic parts by means of selective laser melting is an emerging technology, the development of which is currently of great interest. The quality of the parts produced is evaluated mainly in terms of their mechanical properties, dimensional accuracy, and the homogeneity of the material. Because it is virtually impossible to produce parts without any internal porosity using powder-based additive manufacturing processes, measuring the porosity is critically important to optimizing the processing parameters. X-ray computed tomography is currently the only way used to measure the distribution of pores non-destructively and it can also measure the density and dimensional accuracy. Many studies have presented results of porosity measurements made using CT, but no standard methodology for the making of measurements and processing of data currently exists. The choice of parameters used for measurement and processing can have a significant impact on the results. This study focuses on the effect of voxel resolution on the resulting porosity number and discusses the possibilities for determining the threshold value for detecting pores. All the results presented in this study were obtained by analyzing the sample produced by selective laser melting technology from AlCu2Mg1.5Ni alloy.

Abstract: A low frequency electromagnetic field was introduced into the direct chill (DC) casting process and the ingots of Al-Cu alloy were prepared to study the macrosegregation behaviour of the ingots under the influence of the electromagnetic field. The experimental results showed that there is an obvious positive segregation near to the surface and a negative segregation in the centre area of the ingot. Cu shows the highest segregation tendency among the main elements of Cu, Mg and Mn. Grain refiner element Ti shows a segregation trend opposite to that of Cu. With the application of electromagnetic field, the negative centreline segregation in the centre area of the ingot was evidently reduced although it didn’t show significant effect on the segregation near to the ingot surface. A significant grain refinement was also achieved with the application of electromagnetic field. The mechanism of the reduction of macrosegregation with electromagnetic field was also analyzed in the present work.

Abstract: The effect of precipitate on microstructure evolution and hardness of Al-Cu alloy during torsion deformation has been investigated, by comparing the evolution of microstructure in aged Al-2wt.% Cu alloy with commercial purity aluminum (1100Al). The microstructure evolution is studied by Transmission Electron Microscopy and Electron Backscatter Diffraction, and hardness is measured using Vickers hardness measuring instrument. It is found that the presence of precipitate enhance the grain refinement and hardness of Al-Cu alloy. By applied equivalent strain of 3.26, the (sub) grain size of 86 nm is achieved. In contrast, the presence of precipitate is found to be inhibiting the development of high angle grain boundary.

Abstract: Synchrotron X-ray radiography was used to in-situ study the growth of equiaxed dendrite during the solidification of Al-20 wt.% Cu alloy. Equiaxed dendrites with two different morphologies were formed in nearly isothermal conditions. The image processing was used to improve the image quality. The time evolution of the primary dendrite arm length and the corresponding growth rates were analyzed. The experimental results indicated that the solute interaction was the main factor to influence the equiaxed dendrites growth. Besides, the rotation and floating of the dendrites were also observed during the early growth phase.

Abstract: Al-5.0Cu-0.6Mn-0.6Fe alloy was obtained for the first time using ultrasonic vibration and squeeze casting simultaneously. The effect of ultrasonic vibration and applied pressure on the microstructures and hardness of Al-5.0Cu-0.6Mn-0.6Fe alloy were studied. The results indicated that the ultrasonic vibration and applied pressure promoted the formation of smaller α-Al globular grains. In particularly, with the treatment of ultrasonic vibration or applied pressure during solidification, the brittle Fe-rich imtermetallic compounds in Al-5.0Cu-0.6Mn-0.6Fe alloy became more refined and changed from Chinese script shape to polyhedral shape, which improved the mechanical property. Furthermore, these effects on the grain refinement and Fe-rich intermetallic compounds became more significant by using ultrasonic vibration and applied pressure concurrently during solidification. This process technology is helpful for the development of high performance aluminum alloys with low cost as well as for green casting.