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Al-5Cu-0.8Mn-0.1Zr strips produced during a twin-roll-casting process are investigated in this paper. Central segregation does occur in the alloy strip, and the segregation is a mixture of Al2Cu and Al20Cu2Mn3 eutectic phases. This mixture is difficult to be dissolved in solid solution heat treatment. In this paper, nano-sized TiC/TiB2 particles are introduced in the process of twin-roll-casting. It was found that after adding 0.3% nano-sized TiC-TiB2 particles, the composition distribution becomes more uniform, and the central segregation is eliminated, compared to the strip without nanoparticles. The tensile strength of T6-treated alloy increases from 350 MPa to 390 MPa when nanoparticles are added, and the goal of increasing the properties of twin-roll-cast Al-Cu-Mn-Zr alloy has been achieved. [ABSTRACT FROM AUTHOR]

The increase in strength usually accompanies with ductility loss in structural materials. We proposed a novel approach to the design and fabrication of hierarchically structured Al-Mg-Si alloys/nanocomposites with improved strength and ductility. The layered distribution of TiC nanoparticles (TiCp), bimodal-sized grains and precipitates were produced in a laminated composite composed of Al-Mg-Si matrix alloy and TiCp/Al-Mg-Si composite by accumulative roll bonding (ARB), increasing yield strength from 380 MPa to 443 MPa with a uniform elongation from 5.0% to 6.4%, compared to the ARB TiCp/Al-Mg-Si composite. This work provides a new strategy for producing high strength composite sheets for industrial applications. A hierarchical structure with the layered distribution of nanosized TiC particles (TiCp) was obtained through the master alloy-casting process and accumulative roll bonding process. Significant improvement in strength was obtained with no loss in ductility. [ABSTRACT FROM AUTHOR]

In this work, a high strength–ductility Ti64 cast alloy, containing trace TiC-TiB2 nanoparticles, was fabricated by adding dual-phased nano-TiC-TiB2/Al master alloys to the molten Ti64 alloys. The trace addition of the TiC-TiB2 nanoparticles (0.1 wt%) simultaneously reduced the size of the β grains, the α laths, and the α colony size of the lamellar structure during casting and suppressed the coarsening of the α laths during heat treatment. The yield strength and the uniform elongation of TiC-TiB2/Ti64 were increased by ~130 MPa and 2%, respectively. The simultaneously improved strength and ductility of the TiC-TiB2/Ti64 were attributed to the decrease in the α colony size of the lamellar structure, the significant refinement of the grains and α laths, and the pinning effect of nanoparticles. [ABSTRACT FROM AUTHOR]

Fatigue resistance and fracture toughness are essential to the reliability of castings during service. Reducing microporosity in cast alloys is a crucial issue for improving their fatigue strength and fracture toughness. Here we report a significant reduction in microporosity of a cast aluminum-copper alloy developed using in situ TiC nanoparticle additions coupled with a stir-casting method. The addition of TiC nanoparticles is found to improve the interdendritic feedability of liquid metal and as a result reduces the volume fraction of microporosity by two orders of magnitude compared to a conventionally cast Al–Cu alloy. This method, which is mechanistically associated with a pore-dominated process, acts to significantly improve the fatigue strength, fracture toughness and uniform elongation of the cast Al–Cu alloy to values which, to the best of our knowledge, represent the highest ever achieved for a cast aluminum alloy. Image 1 • A significant porosity reduction is achieved in Al cast alloy through an in-situ nanoparticle master alloy method. • This method serves to uniformly add nanoparticles into metal melt and improve the bonding between particles and matrix. • The addition of TiC nanoparticles impedes the formation of porosity and thus improves the mechanical property of Al alloy. • The fatigue strength, fracture toughness and elongation of the Al alloy are improved to 114 MPa, 55 MPa m1/2 and 12%. • The mechanism of the mechanical property improvement are revealed with the aid of finite element modeling. [ABSTRACT FROM AUTHOR]

In this work, two types of Al-Mg-Si strips with different Mg/Si ratios were fabricated by vertical-type twin-roll casting (TRC), and the effect of the Mg/Si ratio on microstructure and tensile properties of the TRC strips was investigated. The TRC strips show the heterogeneous structure, composed of columnar dendrites near the surface of both sides and near-equiaxed grains in the central region. Serious central segregation of eutectic phases occurred in the TRC strips with Mg/Si = 0.5 (S0.5), while no obvious central segregation was found in the strips with Mg/Si = 2.9 (S2.9), which was ascribed to the different solidification path. The low Mg/Si ratio promoted precipitation during aging, which resulted in an increase of 85 MPa in yield strength compared to the S2.9 sample. However, intergranular fracture occurred in the S0.5 sample, lowering uniform elongation. • The Mg/Si ratio affects the solidification path of Al-Mg-Si alloy. • High Mg/Si ratio inhibits central segregation and grain growth. • Serious central segregation occurred in the TRC strips with a low Mg/Si ratio. • The sample with a higher Mg/Si ratio has the higher elongation. [ABSTRACT FROM AUTHOR]