Rheo-diecasting Samples Research Articles

Influence of rheo-diecasting processing parameters on microstructure and mechanical properties of hypereutectic Al–30%Si alloy

The effects of pouring temperature, vibration frequency, and the number of curves in a serpentine channel, on the microstructure and mechanical properties of Al–30%Si alloy processed by rheo-diecasting (RDC) were investigated. The semisolid Al–30%Si alloy slurry was prepared by vibration serpentine channel pouring (VSCP) process in the RDC process. The results show that the pouring temperature, the vibration frequency, and the number of the curves strongly affect the microstructure and mechanical properties of Al–30%Si alloy. Under experimental conditions of a pouring temperature of 850 °C, a twelve-curve copper channel and a vibration frequency of 80 Hz, the primary Si grains are refined into fine compact grains with average grain size of about 24.6 μm in the RDC samples assisted with VSCP. Moreover, the ultimate tensile strength (UTS), elongation and hardness of the RDC sample are 296 MPa, 0.87% and HB 155, respectively. It is concluded that the VSCP process can effectively refine the primary Si grains. The refinement of primary Si grains is the major cause for the improvement of the mechanical properties of the RDC sample.

Effect of rheo-diecast process on the mechanical properties of A390 alloy by serpentine channel

In this paper, the effects of rheo-diecast process parameters and T6 heat treatment on the microstructure and mechanical properties of the rheo-diecasting (RDC) semi-solid A390 alloy prepared through pure copper serpentine channel were investigated. The results indicate that the mechanical properties of the RDC samples change with the pouring temperature and injection pressure. In this case, a lower pouring temperature results in better tensile strength and elongation of the RDC A390 alloy; however, the tensile strength and elongation decrease when the pouring temperature decreases to 660°C. Higher injection pressures result in the improved mechanical properties of the RDC A390 alloy. To some extent, T6 heat treatment improves the tensile strength and ductility of the RDC A390 alloy compared to those of the non-heat treated alloy. However, when the pouring temperature and injection pressure are greater than 670°C and 70 MPa, respectively, the mechanical properties are sharply diminished.

Microstructure and properties of rheo-diecasting wrought aluminum alloy with Sc additions

In this paper semisolid slurry of Al-6.3Zn-1.9Mg-1.8Cu-0.15Zr alloy with different levels of Sc was prepared, and the effect of Sc content on the morphology of microstructure and mechanical properties of the rheo-diecasting samples was investigated. The results indicate that the excellent semisolid slurry of the wrought Al alloy could be obtained with the addition of 0.22%Sc. Sc additions not only influenced the morphology of the primary α-Al particles in the slurry, but also promoted the formation of fine α-Al globules in the solidification process of the remaining liquid, which contributed to the considerable improvement in tensile strength and elongation. The tensile strength and elongation of the rheo-diecasting samples with 0.45%Sc after T6 heat treatment increased by 82% and 147% respectively compared to the die-casting samples of the base alloy.

Microstructure and property of rheocasting aluminum-alloy made with indirect ultrasonic vibration process

Abstract This paper reports a new slurry-making process with indirect ultrasonic vibration (IUV), in which the horn is vibrated under the outside of the metallic cup containing alloy melt. Semisolid slurry of A356 Al alloy was prepared by this process, and the effects of IUV treatment time on the morphology of the primary α -Al phase and mechanical properties of rheo-diecasting samples were studied. The results indicate that excellent semisolid slurry of A356 Al alloy could be obtained within 50 s by applying IUV near its liquidus temperature. The sample rheocasted with the slurry made by IUV for 50 s had the maximum tensile strength and elongation, which were 254 MPa and 7.5% respectively.

Preparation and Rheocasting of Semi-solid Aluminum-alloy Slurry with Indirect Ultrasonic Vibration Process

ABSTRACTDirect ultrasonic vibration (DUV) method by dipping the horn into the melt can be used to make semi-solid metal slurry, but application of this process is embarrassed because of the erosion problem of titanium-alloy horn by aluminum melt. In order to avoid this problem, a slurry-making process with indirect ultrasonic vibration (IUV), in which the horn is vibrated under the outside of the metallic cup containing alloy melt, has been developed in this research. Semisolid slurry of A356 Al alloy was prepared by this process, and the effects of IUV treatment time on the morphology of the primary α-Al phase and mechanical properties of rheo-diecasting samples were studied. The results indicate that excellent semisolid slurry of A356 Al alloy could be obtained within 50s by applying IUV near its liquidus temperature, and the average diameter and shape coefficient of the primary α-Al particles were 75μm and 0.62, respectively. IUV treatment time had a significant effect on the mechanical properties of the rheo-diecasting samples, and samples treated by IUV for 50s had the maximum tensile strength and elongation. The maximum as-cast tensile strength and elongation were 244MPa and 7.5% respectively, which were increased by 10% and 75% respectively compared to conventional molten-melt die-casting samples. In addition, the mechanism of preparing semisolid slurry of A356 Al alloy by IUV is discussed.

Study on Rheo-Diecasting for <i>In Situ</i> Synthesized Mg<sub>2</sub>Si/AM60 Composites

Magnesium alloys have high specific strength, specific stiffness, excellent thermal conductivity and casting properties, which have a great prospects development in the industry, However, its low plasticity and ductility limited its application. Magnesium matrix composites can effectively improve its performance. Magnesium alloy die-casting is the main forming process, the conventional high-pressure die-casting (HPDC) defects in multi-cavity type, easy to volume gas, non-heat-treated. Compared with HPDC, the rheo-diecasting (RDC) process has been greatly developed for near-net shape components. In this paper, Mg2Si /AM60 composites is fabricated by in-situ synthesis and semi-solid magnesium matrix composites which are rheoformed in the die-casting machine are prepared by mechanical stirring. The results indicate that the microstructure of composites is non-dendritic and Chinese script type Mg2Si are fine distributed. The fundamental morphology of microstructure by HPDC is dendrite and liquid-phase distributed between dendrite irregularly. The RDC samples have close-to-zero porosity, less segregation, the most of semi-solid of microstructure in rheo-diecasting is spherical or as-spherical structure.

Preparation and rheocasting of semisolid slurry of 5083 Al alloy with indirect ultrasonic vibration process

Abstract The indirect ultrasonic vibration (IUV) method, in which the horn was vibrated under the outside of the metallic cup containing alloy melt, was employed for preparing semisolid slurry of 5083 Al alloy in this work. The effect of IUV on the microstructure of semisolid slurry and mechanical properties of rheo-diecasting samples were studied. The results indicate that good semisolid slurry could be obtained when the melt treated by IUV for 50 s, and the average diameter and shape coefficient of primary α-Al particles were 60 μm and 0.54 respectively. Apart from preparing semisolid slurry with fine microstructure, IUV had degassing effect on semisolid slurry of 5083 Al alloy. The tensile strength and elongation of the rheo-diecasting samples were 283 MPa and 9% respectively, which were increased by 11.4% and 32.4% respectively compared to conventional liquid die-casting samples.

Microstructure and mechanical properties of rheo-diecasted A390 alloy

The microstructure and mechanical properties of the rheo-diecasting (RDC) A390 alloy under as-cast and T6 heat treatment conditions were investigated. The results indicate that the RDC sample has fine and uniform microstructure throughout the sample under the as-cast condition, and the average size of primary Si spheroids is 20-30 μm. Meanwhile, the intermetallic compounds in RDC sample are reduced. Compared with the alloy produced by conventional liquid die-casting(LDC), RDC samples have improved tensile strength, ductility, hardness and wear resistance. It is also found that heat-treatment of the RDC A390 alloy under T6 condition, can substantially improve mechanical properties, with the tensile elongation more than 100% improvement.

Development of Rheo-Diecasting of Al-Si Alloys Based on a Modified DSCP Process

An advanced rheo-diecasting technique, based on a modified multi-electromagnetic stirring continuous preparation (MSCP) process was developed for manufacturing near-net shape Al-alloys components with high integrity. The modified MSCP process innovatively combines noncontact electromagnetic stirring and an annular chamber with specially designed profiles to in situ make high quality semisolid slurry, and intensive forced shearing and self-wiping action can be achieved under high shear rate and high intensity of turbulence inside the annular chamber. Three Al-Si alloys with hypoeutectic, eutectic and hypereutectic compositions were tested in this study. The results indicate that, compared with those produced by conventional high-pressure diecasting (HPDC) process, rheo-diecasting samples based on the modified MSCP process have finer and more uniform microstructure.

Rheo-diecasting process for semi-solid aluminum alloys

A novel one-step semisolid processing technique, the rheo-diecasting (RDC) process, was developed, which adapts in situ creation of semisolid metal slurry with fine and spherical solid particles followed by direct shaping of the slurry into a near-net shape component using the existing cold chamber diecasting process. The RDC process was applied to process A356 and A380 aluminum alloys. The resulting microstructures and mechanical properties of RDC products under as-cast and various heat treatment conditions were analyzed. The experimental results show that the RDC samples have an extremely low porosity, a fine and uniform microstructure throughout entire casting, and consequently much improved strength and ductility in the as-cast condition. The strength of RDC A356 alloy can be substantially improved under T5 and T6 heat treatments without loss of ductility.

Microstructure and mechanical properties of rheo-diecast AZ91D magnesium alloy

A new semisolid metal processing technology, rheo-diecasting (RDC) has been developed for production of Mg-alloy components with high integrity. The RDC process innovatively combines the dispersive mixing power of the twin-screw mechanism for creation of high quality semisolid slurry and the high efficiency, low cost nature of the high pressure die casting (HPDC) process for component shaping. AZ91D Mg-alloy was used to optimise the RDC process and to establish its advantages over both the HPDC process and other existing semisolid processing techniques. In this paper we present the RDC process for processing Mg-alloys and the resulting microstructure and mechanical properties of RDC AZ91D alloy. The solidification behaviour of the Mg-alloys in the RDC process and the co-relationships between microstructure and mechanical properties of the RDC AZ91D alloy are discussed. It was found that the RDC process is capable of producing Mg-alloy samples with close-to-zero porosity and a fine, uniform microstructure throughout the entire sample irrespective of the section thickness. Compared with those obtained by other existing processing techniques, the RDC samples have substantially improved or equivalent mechanical properties, with the tensile elongation showing more than 100% improvement.

Development of the rheo-diecasting process for magnesium alloys

The rheo-diecasting (RDC) process is an innovative one-step semisolid processing technique for manufacturing near-net shape components of high integrity directly from liquid Mg-alloys. The process innovatively adapts the well-established high shear dispersive mixing action of the twin-screw mechanism to the task of in situ creation of semisolid metal (SSM) slurry with fine and spheroidal solid particles followed by direct shaping of the SSM slurry into a near-net shape component using the existing cold chamber high pressure diecasting (HPDC) process. In this paper, we present the RDC process, and the resulting microstructures and mechanical properties of various Mg-alloys. The experimental results show that the RDC samples have extremely low porosity (typically 0.1–0.3%), fine and uniform microstructure throughout entire casting, and consequently much improved strength and ductility, compared with those produced by the HPDC process and other semisolid processes. In addition, the RDC process is more tolerant to alloy composition in terms of processability.