Fig 2 - uploaded by Ren-guo Guan
Content may be subject to copyright.
Source publication
A semisolid slurry of AZ31 magnesium alloy was prepared by vibrating wavelike sloping plate process, and the semisolid die forging process, microstructures, and properties of the magnesium alloy mobile telephone shell were investigated. The semisolid forging process was performed on a YA32-315 four-column universal hydraulic press. The microstructu...
Similar publications
This study investigated the flexural characteristics of slurry infiltrated fibrous concrete made with miraculous berry fiber (thaumatococcus daniellii) thereby assessing its potentials as a replacement for steel reinforcing material for economical construction methods. The stems of the miraculous berry plant were collected, freed of their inner cen...
Citations
The objective of this chapter is to understand what are semisolid alloys and its requirements in terms of liquid to solid transition (in Rheocasting processes) or solid to liquid transition (in Thixoforming), key to understanding Semisolid Materials technology. The chapter exploits the few commercial alloys available for SSM and describes the concepts involved in the development of SSM materials.
Thixoforming has unique characteristics over the traditional casting and forging processes, but there is few research focusing on thixoforming of nickel-based superalloys. In this paper, nickel-based superalloy GH4037 parts were successfully formed by thixoforming with different parameters. The effects of forming temperature, soaking time and dwell time on the microstructure and mechanical properties of the formed parts were investigated. The results indicated that forming temperature and soaking time exerted a crucial role in microstructure evolution. With the increase of temperature and soaking time, the proportion of liquid phases in the microstructure increased. During thixoforming, liquid phases were squeezed from the middle region to the peripheral region, resulting in more liquid phases at the edge of the parts. MC-type carbides rich in Ti, V, W and Mo were observed in the liquid phases. When semi-solid billet was heated at 1380 °C for 30 min, the best mechanical properties including an ultimate tensile strength of 973 MPa, a yield strength of 634 MPa and an elongation of 45.6% were achieved. The dwell time had a slight effect on the microstructure and mechanical properties of the parts. The fracture surfaces of the tensile specimens exhibited mostly dimple surfaces and presented a transgranular ductile fracture mode.
This paper focuses on the time evolution of the microstructure of liquid-like semisolid metal slurries and provides a model to investigate the origins of pseudoplasticity and thixotropy of semisolid metal slurries. The model could not only be used to predict the steady-state apparent viscosity but also to further elucidate the instantaneous rheological behavior of the semisolid metal slurry with a time-dependent solid volume fraction and a time-dependent shear rate, and it is successfully applied to analyze the rheological behavior of the semisolid slurry of magnesium alloy AZ91D. The calculated results point out that the specific rheological behavior of semisolid metal slurries roots in the time evolution of their microstructure, while the external flow conditions influence the rheological behavior of semisolid metal slurries by changing their microstructure. Furthermore, the calculated results also indicate that the stir’s braking from a certain steady state will lead to further agglomeration and the agglomeration degree will be aggravated during remelting semisolid metal billets.
In the backward slip zone, the buckling direction of the isothermal lines near the surface of the alloy was toward the exit of the roll gap, the buckling direction of the isothermal lines at the centre was toward the entrance of the roll gap and semisolid metal deformation happened. In the forward slip zone, the buckling direction of the isothermal lines was toward the exit of the gap, the bending degree increased from the neutral flow plane to the exit of the roll gap and solid metal deformation took place. The microstructure of the strip became more refined with the decrease in casting temperature. When the casting temperature was between 670 and 690°C and the rolling speed was 0·167 m s−1, the alloy AZ31 strip with cross-section size of 4×160 mm was prepared. The mechanical properties of the product were higher than that of conventional roll casting.
A novel short process for producing A2017 alloy strips with notable features of near net shape, saving energy, low cost, and high product performance was developed by combining semisolid rolling, deep rolling, and heat treatment. The microstructure and properties of the A2017 alloy strips were investigated by metallographic microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, tensile testing, and hardness measurement. The cross-sectional microstructure of the A2017 alloy strips is mainly composed of near-spherical primary grains. Many eutectic phases CuAl2 formed along primary grain boundaries during semisolid rolling are crushed and broken into small particles. After solution treatment at 495°C for 2 h the eutectic phases at grain boundaries have almost dissolved into the matrix. When the solution treatment time exceeds 2 h, grain coarsening happens. More and more grain interior phases precipitate with the aging time prolonging to 8 h. The precipitated particles are very small and distribute homogenously, and the tensile strength reaches its peak value. When the aging time is prolonged to 12 h, there is no obvious variation in the amount of precipitated phases, but the size and spacing of precipitated phases increase. The tensile strength of the A2017 alloy strips produced by the present method can reach 362.78 MPa, which is higher than that of the strips in the national standard of China.
The objective of this chapter is to understand what semisolid alloys are and what are their requirements in terms of liquid to solid transition (in rheocasting processes) or solid to liquid transition (in thixoforming), key to understanding semisolid materials technology. The chapter exploits the few commercial alloys available for semisolid metals (SSMs) and describes the concepts involved in the development of SSM materials. © 2014 Elsevier Ltd All rights reserved.
Semisolid stir joining of AZ91 alloy was investigated by using mechanical stirring and Mg–25 wt%Zn interlayer. A 2 mm-thick interlayer was located between two 7.5 mm-thick AZ91 pieces. Then, they were heated to 530 °C, the semisolid temperature of both base metal and interlayer. A stirrer with a rotational speed of 1600 rpm was introduced into the weld seam. Optical microscopic and scanning electron microscope (SEM) investigation, microhardness test, shear punch test (SPT), and three points bending test were carried out to assess the properties of the joint. Results showed three distinctive zones: stir zone (SZ), compacted zone (CZ), and diffusional–mechanical affected zone (DMAZ). SEM and X-ray diffraction (XRD) analysis also indicated a wide range of compounds formed in the different zones. The macroscopic image also showed advancing and retreating sides with different DMAZ widths. Proper metallurgical bonding was achieved due to the satisfactory mixing of base metal and interlayer in the semisolid condition. Shear punch test also showed decent ultimate shear strength of the weld metal.
