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Aikerly Mg alloy forming processes
Magnesium alloy forming processes can mainly be divided into liquid state forming processes and solid state forming processes. Liquid state forming processes include gravity casting, low-pressure casting, die casting, and semi-solid casting, while solid state forming, also known as plastic processing forming, includes extrusion, forging, rolling, and so on.
Aikerly Liquid State Forming Processes-Casting
1.1 Gravity Casting Magnesium alloy can be produced using different gravity casting methods, such as sand casting, investment casting, metal mold casting, semi-metal mold casting, shell mold casting, etc.
1.2 Low-Pressure Casting Low-pressure casting's stable filling and sequential solidification characteristics can produce high-quality magnesium alloy castings.
1.3 Die Casting Vacuum die casting, oxygen-filled die casting, and semi-solid die casting. Vacuum die casting first removes the gas in the cavity during the die casting process to reduce or eliminate the pores and dissolved gas in the casting, improving the mechanical properties and surface quality of the casting. Oxygen-filled die casting is where oxygen or other active gases are injected into the cavity before the molten metal fills it. During the filling process, the active gas reacts with the molten metal to generate dispersed metal oxides, achieving the goal of eliminating gas and pores inside the casting. Semi-solid die casting can be divided into rheological die casting and thixotropic die casting. Rheological die casting directly transfers the prepared semi-solid slurry to the pressure chamber for die casting, while thixotropic die casting re-heats the pre-made fine-grained semi-solid ingots to the semi-solid range for die casting.
1.4 Semi-Solid Casting
Semi-solid forming can be divided into rheological forming and thixotropic forming. Among them, thixotropic injection molding is the most mature, with the advantages of simple process and high degree of automation, and has been widely used in magnesium alloy production.
Aikerly Solid State Forming Processes
The solid-state forming processes for magnesium alloys mainly include the following methods:
2.1 Extrusion: Due to the relatively poor plasticity of magnesium alloys, extrusion is a suitable forming method, typically using warm extrusion and hot extrusion. Extrusion processes are used for producing magnesium alloy pipes, rods, profiles, and strips.
2.2 Forging: Magnesium alloy forging can be classified into free forging and die forging. Commonly used magnesium alloys for forging include the ZK series and AZ series. After heating, the magnesium alloy billet undergoes punching and forging in a heated mold. Ordinary mechanical forging machines can be used, and the key to the technology lies in the design of forming molds and processes, as well as the control of mold temperature, deformation rate, and deformation speed parameters. Compared to casting and semi-solid forming processes, this technique offers advantages of high production efficiency, high product yield, and low cost.
2.3 Rolling: Magnesium alloy strips and plates are usually produced using rolling forming methods. In the rolling process, the magnesium alloy billet is pressed into the desired flat plates or strips through rolling with the use of rollers.
In addition to these three main solid-state forming processes, there are other methods such as powder forging and isothermal pressing. These processes can be chosen based on specific product requirements and process characteristics to manufacture various shapes and sizes of high-quality magnesium alloy parts and components. Solid-state forming processes find widespread applications in aerospace, automotive, electronics, and other fields because they avoid issues related to oxidation and thermal expansion at high temperatures in liquid-state processes, while also offering advantages for complex-shaped components.
Aikerly Advanced Manufacturing Processes
Magnesium Thixomolding technology
Thixomolding technology is an advanced forming method specifically used for processing magnesium alloys. It is derived from the abbreviation "Magnesium Injection Molding" and is also known as "Thixoforming" or "Semi-Solid Forming."
Thixomolding technology uses magnesium alloy chips as raw materials, which are heated electrically in the machine barrel to reach a semi-solid state. By applying shear force to the semi-solid alloy, the dendritic solid is transformed into spherical particles, reducing viscosity and increasing fluidity. This entire process can be carried out without the use of SF6 gas and anti-oxidants, and it does not generate waste residue, gas, or industrial waste. Thixomolding technology utilizes the special flow and forming properties of magnesium alloys within the semi-solid temperature range. Within this range, the structure of the magnesium alloy consists of partially solid and partially liquid phases, providing it with high fluidity similar to plastic extrusion. This unique semi-solid state facilitates easier injection of the magnesium alloy into the mold and obtaining the desired shape within the mold.
The main steps of Thixomolding technology include:
Raw material preparation: Mixing appropriate magnesium alloy raw materials with other additives to achieve the desired composition and properties.
Heating: Heating the mixture to the semi-solid temperature range, typically below the melting point of the magnesium alloy.
Injection molding: Injecting the heated magnesium alloy into specially designed molds capable of producing complex part shapes.
Cooling: Cooling and solidifying the magnesium alloy inside the mold to maintain the desired shape.
Demolding and post-processing: Removing the molded parts from the mold and performing necessary post-processing, such as removing excess material, surface treatment, and heat treatment.
Compared to traditional methods like melting casting and extrusion forming, Thixomolding technology offers several advantages. Compared to die casting, the advantages of this technology include:
Improved internal quality of castings, reduced porosity, and increased casting density.
High dimensional accuracy of products due to minimal shrinkage during cooling of semi-solid slurry at lower temperatures compared to molten metals.
Excellent mechanical properties with faster cooling rates and fine microstructure.
Enhanced corrosion resistance.
Due to these advantages, Thixomolding technology finds wide applications in aerospace, automotive, electronics, and other industries, especially for the manufacturing of high-strength, lightweight, and complex-shaped components.
Rapid Solidification Magnesium Alloy PFC Process
Rapid solidification magnesium alloy refers to the preparation of magnesium alloy materials through rapid cooling. This method allows the molten magnesium alloy to be rapidly cooled and solidified in a short period, resulting in a very fine grain structure. This fine grain structure can significantly improve the performance of magnesium alloys, including strength, hardness, and wear resistance.
The PFC process stands for Pulsed Fast Cooling, which is a commonly used method for the rapid solidification of magnesium alloys. In the PFC process, high-frequency pulsed electric currents are applied to the molten magnesium alloy, leading to rapid cooling and achieving rapid solidification. This process can create a highly undercooled melt, promoting nucleation and suppressing grain growth, resulting in a fine grain structure.
The preparation of rapid solidification magnesium alloys and the application of the PFC process are relatively complex processes that require precise control of parameters and equipment. Through this process, improved magnesium alloy material properties can be achieved, meeting specific requirements for material strength and performance in particular fields.
GA Process
The GA process refers to Gas Atomization, which is a common method for preparing metal powders. In the gas atomization process, metal alloys are melted and formed into fine droplets through high-pressure gas jetting. These droplets rapidly cool and solidify, forming powder particles. The metal powder particles produced through gas atomization have relatively uniform composition and fine grain structure, making them suitable for preparing high-performance metal alloy materials.
Mg-16%Li (40 at%) alloy refers to a magnesium-16% lithium alloy, where lithium constitutes 40 atomic percent. Magnesium-lithium alloys are a type of lightweight, high-strength metal material with excellent mechanical properties and low density, thus having extensive application prospects in aerospace, automotive, and other fields.
By introducing hydrogen in the GA process, the Mg-16Li-0.12H alloy is developed. This means that during the preparation of the Mg-16%Li alloy, hydrogen gas (H2) is injected into the alloy, resulting in the formation of the Mg-16Li-0.12H alloy. The addition of hydrogen may affect the structure and properties of the alloy, as hydrogen can form hydride phases in metals, influencing the alloy's mechanical properties and hydrogen absorption capacity. This could be a crucial step for researchers in developing β–Mg-Li alloys using gas atomization.
LDC Process
The LDC process stands for "Low-temperature Solution and Aging" process. It is a common metal alloy treatment method used to improve the strength and hardness properties of the alloy.
Mg-Zn-Zr Alloy Treatment Steps:
Low-temperature Solution Treatment: The Mg-Zn-Zr alloy is subjected to a solid solution treatment at a temperature of 413°C for a duration of 5 hours. The solid solution treatment involves heating the alloy to the solidus temperature, allowing its constituents to dissolve uniformly in the solid solution phase. This helps in eliminating grain boundaries and precipitates in the alloy.
Aging Treatment: After the low-temperature solid solution treatment, the alloy is aged at a temperature of 205°C. Aging treatment involves holding the alloy at a relatively lower temperature for a specific period to refine and evenly distribute the precipitates in the alloy. In this case, aging treatment facilitates the refinement and uniform distribution of the Al3Zr phase in the alloy.
Results:Through the combination of low-temperature solid solution and aging treatments, the Mg-Zn-Zr alloy did not exhibit recrystallization or grain coarsening. This indicates that the treatment process effectively suppressed grain growth while maintaining the alloy in a non-recrystallized state. The presence of the Al3Zr phase in the alloy likely played a role in grain refinement during the aging treatment, thereby enhancing the alloy's strength and hardness.
RS (Room Temperature Severe Plastic Deformation) deformed magnesium alloys
RS (Room Temperature Severe Plastic Deformation) deformed magnesium alloys are a type of magnesium alloy material processed through severe plastic deformation at room temperature. The development principle of this process is based on several aspects:
Grain Refinement: One of the main advantages of RS deformed magnesium alloys is the ability to refine the alloy's grains through severe plastic deformation. Grain refinement involves reducing the size of grains, typically measured at the microscale. Smaller grain structures can enhance the alloy's strength and hardness as grain boundaries effectively impede the movement of dislocations, thereby increasing the alloy's plasticity and strength.
Increased Chemical Homogeneity and Improved Damage Resistance: During the RS deformation process, the continuous plastic deformation causes elements in the material to remix, thereby increasing the alloy's chemical homogeneity. Improved chemical homogeneity helps to reduce localized brittleness in the alloy, enhancing its damage resistance and toughness, making it perform better under stress concentration and high-stress environments.
Influence on Hall-Patch Strengthening by Grain Refinement: Grain refinement during the RS deformation process also influences the Hall-Patch strengthening mechanism. Hall-Patch strengthening increases the alloy's strength through dislocation pile-ups at grain boundaries, and grain refinement can increase the quantity of grain boundaries, thus enhancing the Hall-Patch strengthening effect and improving the alloy's strength and hardness.
Formation of Multiphase Dispersion: The RS deformation process can lead to the formation of a multiphase dispersion in the alloy. These multiphase dispersions disperse within the alloy and act as reinforcements under stress, further enhancing the alloy's strength and damage resistance.
Common RS Deformation Techniques:
Equal Channel Angular Extrusion (ECAE): This is a classical RS deformation technique where the magnesium alloy billet is passed through a specially shaped die multiple times, undergoing extrusion and rotation, to achieve grain refinement and improve the material's mechanical properties.
Multi-pass Extrusion: Similar to ECAE, but grain refinement and severe plastic deformation are achieved through multiple extrusions.
High-Pressure Torsion (HPT): This is another common RS deformation method, where the magnesium alloy billet is subjected to high pressure while undergoing simultaneous rotation and extrusion to achieve severe plastic deformation.
Osprey Process
The Osprey Process refers to a specific metal alloy powder preparation technique developed by Osprey Metals or similar companies. Alloys produced using this process typically exhibit excellent chemical homogeneity, smaller grain sizes, and good formability, making them suitable for various powder metallurgy preparation and spray forming applications.