Search

In this study, a new Al–17Si–2.5P master alloy has been successfully prepared to refine primary Si in hypereutectic A390 alloys. By means of electron probe microanalyzer (EPMA), a large number of AlP particles can be found in the Al–17Si–2.5P master alloy. An orthogonal L9(33) test was designed to investigate the integrated effects of refining factors including phosphorus addition level, melting temperature and holding time, and subsequently to optimize the processing parameters. It is found that under the optimized conditions, i.e., phosphorus addition of 375 ppm, melting temperature of 800 °C, and holding time of 30 min, the average sizes of primary Si can be most remarkably decreased from 116 μm to 14 μm with sphere-like morphology. Meanwhile, the Brinell hardness and tensile strength can be significantly increased by 14.1 and 27.8%, respectively. In addition, thermal analysis is also performed with differential scanning calorimeter (DSC) to analyze the solidification process of Al–18Si alloys. [ABSTRACT FROM AUTHOR]

The evolution of three major heat-resistant phases (δ-Al3CuNi, γ-Al7Cu4Ni, T-Al9FeNi) and its strengthening effects at high temperature in Al–Si piston alloys with various Fe/Ni ratios were studied using field emission scanning electron microscope (FE-SEM), electron probe microanalysis (EPMA), and X-ray diffraction (XRD). With the increase of Fe/Ni ratios, the heat-resistant phases begin to evolve in category, morphology, and distribution. The results show that a suitable Fe/Ni ratio will cause the T-Al9FeNi phase to appear and form a closed or semi-closed network with δ-Al3CuNi and γ-Al7Cu4Ni phases instead of the originally isolated heat-resistant phases. As a result, the ultimate tensile strength of the optimized alloy reached 106 MPa with a Fe/Ni ratio of 0.23, which was 23.3% higher than that of base alloy at 350 °C, which is attributed to the fact that a closed or semi-closed network microstructure is advantageous to the bearing of mechanical loads. This work may provide useful ideas for the development of high temperature resistant piston alloys. [ABSTRACT FROM AUTHOR]

In this paper, a new kind of AlTiC–B master alloy, containing large amounts of nano‒sized TiC particles, has been applied in 7050 alloy. The influence of master alloy addition on the casting microstructures, extrusion behaviors and mechanical properties of 7050 has been investigated. It is found that 0.5 wt% addition of AlTiC–B master alloy exhibits the most attractive performance, resulting in much finer matrix grains and less casting defects. After hot extrusion, typical <100> and <111> fiber textures co‒exist in the microstructure of original 7050 alloy, whereas the alloys with AlTiC–B inoculation possess a higher intensity of <111> fiber texture. Besides, the inoculated alloys show better anti–recrystallization performance and larger local misorientation. It has been confirmed that a proper addition of AlTiC–B master alloy is beneficial for the mechanical properties of extruded 7050, which may be due to its refining effect on α–Al grains and its improvement for the precipitation of L1 2 –ZrAl 3. The Brinell hardness, ultimate tensile strength, yield strength and elongation of 7050 alloy with 0.5 wt% addition of AlTiC–B addition are 174 HBW, 665 MPa, 724 MPa and 9.8%, respectively. This work provides a promising prospect of AlTiC–B master alloy for applying in 7050 alloy in industries. • Research highlights: • A new AlTiC–B master alloy with B doped nano‒sized TiC particles was applied on 7050 alloy. • Improvement of casting quality and grain refining can be achieved with AlTiC–B inoculation. • Texture intensity and recrystallization fraction of as‒extruded 7050 vary with AlTiC–B addition. • Mechanical properties can be significantly improved. [ABSTRACT FROM AUTHOR]