Papers by Keyword: Semi-Solid Extrusion

Abstract: The semi-solid thixo-extruded process of AZ91D magnesium alloy with 9 % plastic deformation was investigated. The effect of isothermal time on the thixo-extruded formability of AZ91D magnesium alloy was analyzed. The relationship between isothermal time and microstructure, mechanical property was also researched. The results showed that with increasing the isothermal time from zero to 60 min on 575 °C, the filling distance was increased firstly and then decreased, the solid volume fraction was decreased firstly and then increased, the tensile strength and elongation were also increased firstly and then decreased. However, the increasing isothermal time would lead to decrease of shape factor but the coarsening of particle size. When the isothermal time was 30 min, the solid volume fraction was lowest and the filling distance was greatly increased obviously.

Abstract: Optimising semi-solid processing and accurately modelling semi-solid deformation requires a fundamental understanding of the globule-scale mechanisms that cause the macroscopic rheological response. In this work, apparatus and analysis techniques are being developed for the time-resolved, three-dimensional imaging of semi-solid alloy deformation. This paper overviews synchrotron X-ray tomography results on globular Al-15wt%Cu deformed at 0.7 solid fraction using extrusion. The globule-globule interactions in response to load were quantified in terms of the response of individual globules with respect to globule translation, rotation, and deformation. The potential of time-resolved X-ray tomography in the study of semi-solid alloy deformation is then discussed.

Abstract: Rheo-extrusion of hypereutectic Al-14.8%Si-4.5%Cu-1.1%Mg (in mass%) alloy which is considerably difficult to hot-extrude was tried using semi-solid slurry with fine solid granules and almost finely dispersed primary Si particles, made by a newly developed rotor process. Trials of rheo-extrusion at the constant extrusion ratio of 36 using this semi-solid slurry were carried out at the different conditions of the extrusion temperature and the ram speeds ranging from 520 to 560oC and from 5 to 20mm/s, respectively. Under the all rheo-extrusion conditions, this semi-solid slurry could easily be rheo-extruded to the round bars of 6mm diameter with sound surface at much lower extrusion force than that of hot-extrusion at very low extrusion ratio. In addition, the characteristic age-hardening behavior which is thought to be essential for the rheo-extrusion process has been found out, namely the peak hardness values of aged bars rheo-extruded at 520 and 540oC were considerably higher, 30HV at maximum, than that of a gravity casting.

Abstract: The feasibility of recycling machining grindings of aluminum alloys by semisolid process has been investigated. Machining grindings of A2011 aluminum alloy produced experimentally by lathe machining were used. The material is put into a metal mold and compressed up to 90 % of the true density at room temperature. The metal mold with the compressed machining grindings is heated up to a specified temperature. Afterwards, the metal mold is set into the extrusion container, and extrusion in hot and semisolid range was carried out. In this experimental study, extrusion load, internal structure of the product and mechanical properties (tensile strength, elongation, hardness) of the product are assessed. It was proven that semisolid extrusion is about 40% less extrusion load compared with that of hot extrusion, the shape of the machining grindings remained in the hot extrusion and the semisolid extrusion products extrusion ratios higher than 10 have excellent elongation property, which is comparable to the commercialized product.

Abstract: A 20vol.%SiCw/ZK51A Mg-based composite was fabricated by the process of semi-solid extrusion directly following liquid infiltration. The microstructure and mechanical properties of the composite were investigated in comparison with its squeeze cast and hot extruded counterpart. The results showed that, by semi-solid extrusion, the SiC whiskers were well aligned and microstructure defects associated with the casting technology were eliminated. In addition, as compared with the conventional hot extrusion, the damage to the SiC whiskers during semi-solid extrusion was reduced significantly. Consequently, the composite fabricated by the semi-solid extrusion presented the best whisker reinforcing effect, with its elastic modulus, 0.2% offset yield strength, and ultimate tensile strength achieving 82.5GPa, 383.6MPa, and 431.8MPa respectively.

Abstract: : According to the theory of liquid metal forging and liquid metal extrusion, a new kind of fabricating method for particles reinforced metallic matrix composite was put forward by author. In this paper, the extrusion process to semisolid thick liquid after the mixture was studied by means of the theoretical analysis and experimental methods. Mechanical characteristics of solidification during flowing and plastic deformation during solidification of the composite were found. So the base was built up for selecting technology parameters and for building a stabile process