Canfeng Fang

Effects of ultrasonic vibration on solidification structure and properties of Mg-8Li-3Al alloy

Abstract Ultrasonic vibration was introduced into the Mg-8Li-3Al alloy melt during its solidification process. The microstructure, corrosion resistance and mechanical properties of the Mg-8Li-3Al alloy under ultrasonic vibration were investigated. The experiment results show that the morphology of a phase is modified from coarse rosette-like structure to fine globular one with the application of ultrasonic vibration. The fine globular structure is obtained especially when the power is 170 W, and the refining effect also gets better with prolonging the ultrasonic treatment time. The corrosion resistance of the alloy with 170 W of ultrasonic vibration for 90 s is improved apparently compared with the alloy without ultrasonic vibration. The mechanical properties of alloys with ultrasonic vibration are also both improved apparently. The tensile strength and elongation of alloy improve by 9.5% and 45.7%, respectively, with 170 W of ultrasonic treatment for 90 s.

Microstructure of Al-Zn-Mg-Cu-Zr-0.5Er alloy under as-cast and homogenization conditions

Abstract The billets of Al-Zn-Mg-Cu-Zr and Al-Zn-Mg-Cu-Zr-0.5Er alloys were prepared by semi-continuous direct chill casting (DCC). The effects of trace Er on microstructure of Al-Zn-Mg-Cu-Zr alloy under as-cast and homogenization conditions were studied. The results show that the grain morphology is large dendritic structure and the grain size increases obviously by the addition of 0.5% Er. Moreover, most of Er element in the alloy segregates at grain boundary during solidification, resulting in ternary Al8Cu4Er phase. After homogenization, most of the MgZn2 phase at grain boundary has dissolved back to Al matrix in the two alloys. In the Er-containing alloy, the dissolution temperature of Al8Cu4Er phase is about 575 °C. Therefore, the homogenization treatment cannot eliminate Al8Cu4Er phase validity.

Effects of yttrium on microstructure and mechanical properties of Mg-Zn-Cu-Zr alloys

Abstract The effects of yttrium addition on microstructure and mechanical properties of as-cast Mg-6Zn-3Cu-0.6Zr- x Y ( x =0, 0.5, 1.0, 1.5 and 2.0, mass fraction, %) (ZCK630+ x Y for short in this study) alloys were investigated by means of OM, XRD and SEM. The results show that the average grain size of Mg-Zn-Cu-Zr magnesium alloy is effectively reduced (from 57 μm to 39 μm) by Y addition. The analysis of XRD indicates the existence of I-phase (Mg 3 Zn 6 Y) and W-phase (Mg 3 Zn 3 Y 2 ) in ZCK630 alloys with Y addition. The ultimate tensile strength of ZCK630 alloys is significantly deteriorated with increasing Y addition, which is possibly related to the continuous networks of intergranular phases and the increase of W-phase.

Effect of neodymium, gadolinium addition on microstructure and mechanical properties of AZ80 magnesium alloy

Abstract The microstructure and mechanical properties of AZ80 magnesium alloys with varying Nd, Gd contents were investigated. The results revealed that the as-cast microstructure of AZ80 alloy was composed of α-Mg matrix and divorced eutectic β-Mg 17 Al 12 phases. The fraction of Mg 17 Al 12 phase was reduced when 0.6 wt.% Nd was added, and new rod-shaped Al 11 Nd 3 phase and small block-shaped Al-Nd-Mn phase appeared. With Gd addition, the Gd elements mixed with Nd to form rare earth phases. New block-shaped Al 2 Gd and Al 2 Nd phases which were collectively called Al 2 RE phases were observed in the microstructure with more than 0.6 wt.% Gd addition. Moreover, the addition of Gd could promote the precipitation of block-shaped Al 2 RE phase, and inhibit the original rod-shaped Al 11 Nd 3 phase. The AZ80-0.6Nd-0.6Gd alloy exhibited the optimal mechanical properties among all the experimental alloys, in which the tensile strength, yield strength and elongation were 215, 145 MPa and 8.33%, respectively.

Effect of Gd on the Microstructure and Mechanical Properties of Mg-Sn-Zn-Al Alloy

The effect of Gd addition on the microstructures and mechanical properties of Mg-5Sn-Zn-Al alloy was investigated with variations of Gd contents. These results show that adding Gd can effectively refine the grain size and growth. In addition, the solubility of Gd increases the lattice constants of α-Mg phase. Accordingly, the tensile properties of the as-cast Mg-5Sn-Zn-Al alloy are improved by the addition of Gd. The Mg-5Sn-Zn-Al-0.4Gd exhibits the highest tensile properties, and the values of the yield and ultimate tensile strength and elongation are 111 MPa, 188 MPa and 18.0%, respectively.

In Situ TiB2 and Al2(Y, Gd) Particles Reinforced Magnesium Matrix Composite with Al-Ti-B Addition

In-situ micro/nanosized TiB2 and Al2(Y, Gd) particles reinforced magnesium matrix composite was successfully fabricated by addition of Al-Ti-B preform into Mg-Gd-Y-Zn matrix alloy, its microstructures and properties were investigated. The results show that the introduction of Al-Ti-B preform causes the precipitation of Al2(Y, Gd) particles and the SHS synthesis of TiB2 particles which significantly refine solidification structure. The reinforced Al2(Y, Gd) particles with average sizes of 5-8 μm are uniformly distributed throughout the magnesium matrix, and have a good bond to the matrix. Tensile tests indicate that, compared with the former matrix alloy, mechanical properties of the multiple in-situ particles reinforced composite are improved all-roundly.

Effect of Hot Extrusion on the Microstructure of In Situ TiB2 Particulate Reinforced Magnesium Matrix Composite

The TiB2/AZ31 magnesium matrix composite was fabricated via self-propagating hightemperature synthesis (SHS) and then hot extruded. The influence of hot extrusion on the microstructure and property of TiB2/AZ31 composites was investigated. The results show that hot extrusion and synthesized TiB2 particles could refine the grain size obviously. The synthesized TiB2 particles are micro- and nano-sized, dispersing homogenously in the matrix. The interface between the matrix and the particles are good bonding. Meanwhile, slip and twinning are the main deformation modes during the hot extrusion. The fracture surface of hot-extruded TiB2/AZ31 magnesium matrix composite has more dimples than the as-cast AZ31 magnesium alloy. The improvement of microstructure seems to be beneficial for the fracture ductility of TiB2/AZ31 magnesium matrix composite.

A 3-D Mathematical Model of Thermal Field Evolution in the Direct Chill Casting of Superlight Magnesium Alloy Slabs

Abstract A mathematical model of the direct chill (DC) casting process for superlight Mg-Li alloy (LA141) slab has been developed using the finite differential method (FDM). Thermal boundary conditions including primary and secondary cooling conditions have been selected based on knowledge of the physical process and the literatures. The variations of heat transfer coefficient between slab and dummy block interface resulting from the deformation of the slab have been considered. By calculating the temperature distribution, solid-liquid interface shape and position, the influence of casting parameters on DC casting process, such as the pour temperature, cooling water flow rate and casting speed have been analyzed. Moreover the profiles of the solidification fronts during the casting processes for the alloys of LA141 and AZ31 are compared.

EFFECT OF Al-Ti-B ON MAGNESIUM ALLOY MICRO-ALLOYED WITH Ca

Effect of Al-Ti-B master alloy on the microstructure and mechanical properties was investigated in AZ31 magnesium alloys micro-alloyed with Ca. During the casting process, electromagnetic field was also introduced. The results suggest that the micro addition of Ca to magnesium alloy retards the oxidation rate during melting process, improves casting qualities of magnesium alloy ingots. The grain size of AZ31 magnesium alloy has been effectively reduced by optimum addition of 1 wt.% (designed composition) Al-Ti-B master alloy. In this process, the addition level of Ti is the key factor to affect grain size of magnesium alloy, in which two grain refinement mechanisms are built by both TiB2 and residual Ti. Moreover, the electromagnetic field leads to uniform distribution of temperature field and solute field in the molten pool, increases casting qualities and refines grain size further.