Research on a Low Melting Point Al-Si-Cu (Ni) Filler Metal for 6063 Aluminum Alloy Brazing

A new type of low melting point Al-Si-Cu (Ni) filler metal for brazed 6063 aluminum alloy was designed, and the microstructure and properties of the filler metal were systematically studied. The results show that when the content of Cu in the Al-Si-Cu filler metal increased from 10 wt.% to 20 wt.%, the liquidus temperature of the filler metal decreased from 587.8 °C to 533.4 °C. Its microstructures were mainly composed of the α-Al phase, a primary Si phase, and a θ(Al2Cu) phase. After a proper amount of Ni was added to the Al-Si-20Cu filler metal, its melting range was narrowed, the spreading wettability was improved, and the microstructure was refined. Its microstructure mainly includes α-Al solid solution, Si particles, and θ(Al2Cu) and δ(Al3Ni2) intermetallic compounds. The results of the shear strength test indicate that the shear strength of the brazed joint with Al-6.5Si-20Cu-2.0Ni filler metal was 150.4 MPa, which was 28.32% higher than that of the brazed joint with Al-6.5Si-20Cu filler metal.

Microstructure of Al-5Cu-1Li-0.6Mg-0.5Ag-0.5Mn Alloys

Microstructural optimization of Al-Li alloys plays a key role in the adjustment of mechanical properties as well as corrosion behavior. In this work, Al-5Cu-1Li-0.6Mg-0.5Ag-0.5Mn alloy was homogenized at different temperatures and holding times, followed by aging treatment. The microstructure and composition of the homogenized alloys and aged alloys were investigated. There were Al7Cu4Li phase, Al3Li phase, and Al2CuLi phases in the homogenized alloys. The Al7Cu4Li phase was dissolved with an increase in homogenization temperature and holding time. Al2Cu phase and Al2CuLi phase coarsened during the homogenization process. The alloy homogenized at 515 °C for 20 h was subjected to a two-stage aging treatment. Peak-age alloy, which had gone through age treatment at 120 °C for 4 h and 180 °C for 6 h, was mainly composed of α-Al, Al20Cu2Mn3, Al2CuLi, Al2Cu, and Al3Li phases. Tafel polarization of the peak-age alloys revealed the corrosion potential and corrosion current density to be −779 mV and 2.979 μA/cm2, respectively. The over-age alloy had a more positive corrosion potential of −658 mV but presented a higher corrosion current of 6.929 μA/cm2.

Superplastic Deformation of Al–Cu Alloys after Grain Refinement by Extrusion Combined with Reversible Torsion

The binary as-cast Al–Cu alloys Al-5%Cu, Al-25%Cu, and Al-33%Cu (in wt %), composed of the intermetallic θ-Al2Cu and α-Al phases, were prepared from pure components and were subsequently severely plastically deformed by extrusion combined with reversible torsion (KoBo) to refinement of α-Al and Al2Cu phases. The extrusion combined with reversible torsion was carried out using extrusion coefficients of λ = 30 and λ = 98. KoBo applied to the Al–Cu alloys with different initial structures (differences in fraction and phase size) allowed us to obtain for alloys (Al-25%Cu and Al-33%Cu), with higher value of intermetallic phase, large elongations in the range of 830–1100% after tensile tests at the temperature of 400 °C with the strain rate of 10−4 s−1. The value of elongation depended on extrusion coefficient and increase, with λ increasing as a result of α-Al and Al2Cu phase refinement to about 200–400 nm. Deformation at the temperature of 300 °C, independently of the extrusion coefficient (λ), did not ensure superplastic properties of the analyzed alloys. A microstructural study showed that the mechanism of grain boundary sliding was responsible for superplastic deformation.

Kinetic and Strength Calculation of Age-Hardening Phases in Heat-Resistant Aluminum Alloys with Silver

In order to study the microstructures of heat-resistant aluminium alloys with silver in process of aging, kinetic and strength calculation were used to study the equilibrium and metastable phases of Al-4Cu-0.3Mg-0.4Ag alloy system. The main equilibrium phases were Liquid phase, α-Al matrix phase, Al2Cu phase, S phase (Al2CuMg) and AgMg phase, while metastable strengthening phases were Ω phase and θ’ phase. In addition, the kinetic parameters and aging strength of_Ω phase and θ’ phase that precipitated during aging were calculated. The calculated results shows that Ω phase has higher heat-resistant strengthening effect than θ’ phase.

Orientation and Microstructure Evolution of Al-Al2Cu Regular Eutectic Lamellar Bifurcating in an Abruptly Changing Velocity under Directional Solidification

In an abruptly changing velocity under directional solidification, microstructures and the growth orientation of Al-Al2Cu eutectic lamellar were characterized. The change in solidification rate led to an interfacial instability, which results in a bifurcation of the eutectic lamella into new, refined lamellae. The growth orientation of the eutectic Al2Cu phase was also only in its (001) direction and more strongly oriented to the heat flow direction. The results suggest that the eutectic lamellar Al-Al2Cu bifurcation and the spacing adjustment may be caused by the rate determining lateral diffusion of the solutes after interfacial instability.

The Effect of Hold Melt Time against Al-Cu Alloy Hardness and Impact Strength on Recycled Piston and Copper Casting

The product quality and estimation of chemical elements in cast products are determined by the melting of raw materials and the alloying of materials. Copper, silicon, magnesium, zinc, and manganese are alloying elements, which are often added either separately or together to aluminum. The alloy element, when found in aluminum castings, can found of different types of hardenings: solution, age, and work hardenings. In this study, copper was added to the piston recycle casting to obtain a hardening of the dissolution. However, the melting point of copper reaches 1200°C, which is two times higher than the melting point of the piston, reaching 600°C. If casting is done at the melting point of copper, then some elements will be lost, and the solubility of hydrogen gas will be greater as a result of the as-cast recycled piston and the reduced quality of copper like this mechanical properties is decreased. In this study, the former piston was re-melted, and copper pieces were inserted into the melted piston at 600°C and held at 800°C for 60, 75, 90, 105, and 120 minutes. The copper solubility phenomenon in recycling a liquid piston due to diffusion events can be demonstrated by the characteristics and mechanical properties of the as-cast recycled piston and copper added. Hardness, impact, and metallographic test specimens from from recycled as-cast product made with permanent molds. The results of specimen testing show that the longer the holding time, the increase in the hardness value and impact resistance of the specimen, and the formation of the Al2Cu phase increases with increasing holding time. The maximum hardness and durability of 86.3 BHN and 9.6 joules/cm2, respectively, were obtained at a hold melt of 120 minutes. In addition, at a holding time of 90 minutes, the formed Al2Cu phase formation is increase so that the Al phase is decrease

Crystal Structures of Al2Cu Revisited: Understanding Existing Phases and Exploring Other Potential Phases

When processing single crystal X-ray diffraction datasets for twins of Al2Cu sample synthesized by the high-pressure sintering (HPS) method, we have clarified why the crystal structure of Al2Cu was incorrectly solved about a century ago. The structural relationships between all existing Al2Cu phases, including the Owen-, θ-, θ’-, and Ω-Al2Cu phases, were investigated and established based on a proposed pseudo Al2Cu phase. Two potential phases have been built up by adjusting the packing sequences of A/B layers of Al atoms that were inherent in all existing Al2Cu phases. The mechanical, thermal, and dynamical stability of two such novel phases and their electronic properties were investigated by first-principles calculations.