No abstract

In this paper, a new class of Al-Cubased composites which combine the ultrafine lamellar eutectic matrix (α-Al + θ-Al2Cu) and micron-sized primary α-Al dendrites was prepared by progressive solidification. By adjusting the alloy composition and solidification process, the formation of favorable microstructural and micromechanical features can be achieved. The ultrafine lamellar eutectic composite Al94Cu6 exhibits excellent mechanical properties with 472 MPa fracture strength and 7.4% tensile plastic strain. The plasticity of the ultrafine lamellar eutectic composite relies on the volume fraction and work hardening ability of micron-scale primary phase. The present results provide a new perspective for improving the plasticity of the ultrafine lamellar eutectic alloys.

Through the first-principle calculations based on density functional theory and experimental investigation, the structural stability elastic properties and mechanical properties of Ti2Cu and Ti18Cu5Nb1 intermetallics were studied. The first-principle calculations showed that the ratio of bulk modulus to shear modulus (B/G) and Poisson’s ratio (ν) of Ti2Cu and Ti18Cu5Nb1 intermetallics were 2.03, 0.288, and 2.22, 0.304, respectively, indicating that the two intermetallics were ductile. This was confirmed by the compression tests, which showed that the plastic strain of both intermetallics was beyond 25%. In addition, the yield strength increased from the 416 to 710 MPa with the addition of Nb. The increase in strength is the result of three factors, namely covalent bond tendency, fine grain strengthening, and solid solution strengthening. This finding gives clues to design novel intermetallics with excellent mechanical properties by first-principle calculations and alloying.

In this paper, three alloys .4 were prepared by a simple solidification process. By controlling the alloy composition, different microstructures and mechanical properties have been achieved. The Al 81 Cu 13 Si 6 alloy with micro-scale binary eutectic compositions embedded in an ultrafine ternary eutectic matrix exhibits the high yield strength (up to 750 MPa) but fails with a brittle fracture. While the Al 92 Cu 5.6 Si 2.4 alloy with hypereutectic composite structure exhibits the optimum comprehensive mechanical properties with both high tensile strength and ductility. The present results provide a new perspective to prepare Al-based alloy with high strength and ductility by designing the some new composite with optimum microstructure.

In this paper, we prepare the alloys of Zr41.2Ti13.8Cu12.5Ni10Be22.5, Zr44.4Ti14.8Cu14.3Ni11.5Be15, and Zr38Ti12.7Cu9.6Ni7.7Be32 to show the effects of alloy composition on the inhomogeneity structures and mechanical properties of Zr-based bulk metallic glasses (BMGs). Compared with the best glass former Zr41.2Ti13.8Cu12.5Ni10Be22.5, some nanoscale inhomogeneity structures can be induced by shifting the compositions towards a primary phase in the alloys of Zr44.4Ti14.8Cu14.3Ni11.5Be15 and Zr38Ti12.7Cu9.6Ni7.7Be32. The room temperature compression tests reveal that theBMGs contained nanoscale inhomogeneity structures exhibit superior mechanical properties with the high strength of 1780 MPa and especially a remarkable plastic strain of over 9%. These findings provide a new perspective to enhance the ductility of BMGs by introducing nanoscale inhomogeneity structures based on the phase competition strategy.