Comparison of aluminum alloy, zinc alloy, magnesium alloy, and titanium alloy

With the improvement of people's quality of life, the requirements for product aesthetics and quality are also constantly increasing. More and more consumer products are made of alloy materials. Metal materials give people a sense of high-end, sturdy, and durable quality, while traditional plastic shell products are gradually labeled as "cheap" and "low-quality" in the minds of consumers.

For consumer products, commonly used alloy materials include aluminum alloy, zinc alloy, and magnesium alloy. Titanium alloy is commonly used in the medical field due to its good biocompatibility. Fang Gong will take a look at the characteristics of these alloy materials and make a comparison.

Therefore, an inductive summary is placed at the beginning, as shown in the performance comparison table below.

Among these four alloys, titanium alloy is the hardest and has the best strength. In terms of hardness, titanium alloy is much harder than the other three alloys. In terms of tensile strength, titanium alloy is stronger than zinc alloy, followed by magnesium alloy.

Comparison of strength and hardness

But in terms of product structure design, weight also needs to be considered. If the specific gravity is considered for progress, zinc alloy has the highest density and the lowest specific strength. Titanium alloy and magnesium alloy have higher specific strength, but titanium alloy is expensive and has poor workability. Therefore, when considering weight and strength in structural components, magnesium alloy is often used.

Aluminum alloy

The ingredients can be directly found in Du Niang, and it doesn't take much space to list them here. The density of aluminum alloy is 2.63~2.85g/cm, with high strength（ σ B is 110-270MPa, with a specific strength close to that of high alloy steel and a specific stiffness higher than that of steel. It has good casting and plastic processing properties, good conductivity and thermal conductivity, as well as good corrosion resistance and weldability.

Die cast aluminum alloy has good fluidity, with a melting point of 660 ℃.

Aluminum alloy has the most diverse application forms in product structure design, with commonly used processing techniques including die casting, extrusion molding, machining, stamping, and forging. Aluminum alloy profiles are widely used in building doors and windows, and aluminum profiles are also commonly used in mechanical equipment to build frames. The shells of electronic products and fast-moving consumer goods are also made of aluminum alloy, which has high appearance requirements. Common processes include extrusion, machining, stamping, etc.

The shell of fast-moving consumer goods uses less die cast aluminum because die cast aluminum alloy contains a higher content of Si. Therefore, during anodizing, it directly reacts with the solution, resulting in poor surface effect after oxidation. Aluminum castings are commonly used for internal structural components and parts that do not require high appearance requirements. The engine casing of motorcycles requires a complex structure, requiring light weight and sufficient strength. Most of them use aluminum alloy die-casting as the raw material.

Aluminum cast engine casing

Aluminum grade:

The 1xxx series is pure aluminum (with an aluminum content not less than 99.00%), and the last two digits of the series grade are expressed as the percentage point of the lowest aluminum content. The second letter of the brand indicates the modification of the original pure aluminum.

The last two digits of the 2xxx~8xxxxxx series grades have no special significance and are only used to distinguish between different aluminum alloys in the same group. The second letter of the brand indicates the modification of the original pure aluminum.

The 2xxx series is an aluminum alloy with copper as the main alloying element. 2011 fast cutting alloy, with good machinability and high strength. 2018 2218 forging alloy, with good forging properties and high high-temperature strength.

The 3 × × series is an aluminum alloy with manganese as the main alloying element. 3105 3105 building materials, colored aluminum plates, bottle caps.

The 4xxx series is an aluminum alloy with silicon as the main alloying element. 4032 has good heat and friction resistance, and a small coefficient of thermal expansion. Pistons, cylinder heads.

The 5 × × series is an aluminum alloy with magnesium as the main alloying element. 5052 is the most representative alloy of moderate strength, commonly used in sheet metal, ships, vehicles, construction, bottle caps, and honeycomb panels.

The 6XX series is an aluminum alloy with magnesium as the main alloying element and Mg2Si as the strengthening phase. 6063 is a representative extrusion alloy with lower strength than 6061, good extrusion properties, and can be used for complex cross-sectional shapes. It has excellent corrosion resistance and surface treatment properties in buildings, highway guardrails, high railings, vehicles, furniture, household appliances, and decorations.

The 7 × × series is an aluminum alloy with zinc as the main alloying element. 7075 aluminum alloy is one of the alloys with the highest strength, but its corrosion resistance is poor. Covering with 7072 can improve its corrosion resistance, but the cost increases. Aircraft, ski poles.

The 8 × × series is an aluminum alloy with other elements as the main alloying elements

The 9 × × series is a spare alloy group

Aluminum alloys with a tensile strength greater than 480MPa are called high-strength aluminum alloys, mainly based on Al Cu Mg and Al Zn Mg Cu, namely 2XXX (hard aluminum alloys) and 7XXX (super hard aluminum alloys) series alloys. The static strength of the former is slightly lower than that of the latter, but the operating temperature is higher than that of the latter. Due to differences in the chemical composition, melting and solidification methods, processing techniques, and heat treatment systems of alloys, there are significant differences in their performance.

Zinc alloy

Zinc alloy has a low melting point, good fluidity, and is easy to melt and weld. According to manufacturing processes, it can be divided into cast zinc alloys and deformed zinc alloys. Cast zinc alloy has good fluidity and corrosion resistance, and is suitable for die-casting instruments, automotive parts casings, etc. Deformable zinc alloys have good plasticity and ductility, mainly used as battery casings, printed boards, roof panels, and daily hardware. The production of cast alloys is much greater than that of deformed alloys, and for structural components of fast-moving consumer goods, deformed alloys are rarely used. Therefore, the following text only applies to die-casting zinc alloys.

Zinc alloy has a density of 6.3-6.7g/cm and tensile strength σ B is 280-440MPa, with a low melting point and can melt at 385 ℃, making it easy to form by die casting.

Zinc alloy has a significant proportion and the highest flowability among the four alloys described in this article. It has excellent casting performance and can be used to cast precision parts with complex shapes and thin walls. The casting surface is smooth. In the products I designed, the thinnest thickness of zinc alloy die castings is only 0.4mm.

At room temperature, zinc alloy has good strength. It should be noted that zinc alloys are not suitable for use in high and low temperature (below 0 ℃) working environments. Zinc alloys have good mechanical properties at room temperature. However, the tensile strength and impact performance significantly decrease at high temperatures and low temperatures. Zinc alloy has poor corrosion resistance. When the impurity elements lead, cadmium, and tin in the alloy composition exceed the standard, it leads to aging and deformation of the casting. Zinc alloy die-casting parts have aging effect and aging phenomenon, that is, after a long time, the strength naturally decreases and becomes brittle. This is why many people roast that when replacing zinc alloy faucets, they often break brittle, resulting in the thread part of the faucet remaining in the water pipe. Therefore, Fang Gong suggests that when decorating, everyone should try to choose copper faucets instead of zinc alloy ones.

There are currently two main types of standard series used for castings internationally, one is ZAMAK alloy and the other is ZA series alloy. The ZAMAK alloys used include ZAMAK 2, ZAMAK 3, ZAMAK 5, and ZAMAK 7. (For simplicity, the above alloys are collectively referred to as alloys 2, 3, 5, and 7.). The ZA series includes ZA-8, ZA-12, ZA-27, and ZA-35. ZA-8 is mainly used for hot chamber die casting, while ZA-12 and ZA-27 can only be used for cold chamber die casting due to special melting requirements. ZA-35 is generally used for gravity castings. The development of ZAMAK alloy was earlier than that of ZA series alloy, mainly used for pressure casting. The most widely used is No. 3 zinc alloy.

ZAMAK 2: Used for mechanical parts with special requirements for mechanical performance, high hardness requirements, good wear resistance, and general dimensional accuracy requirements.

ZAMAK 3: Good fluidity and mechanical properties. Applied to castings that do not require high mechanical strength, such as toys, lighting fixtures, decorations, and some electrical components.

ZAMAK 5: Good fluidity and good mechanical properties. Applied to castings with certain requirements for mechanical strength, such as automotive parts, electromechanical parts, mechanical parts, and electrical components.

ZA8: It has good impact strength and dimensional stability, but poor fluidity. Applied to die-casting workpieces with small dimensions, high precision and mechanical strength requirements, such as electrical components.

Superloy: With the best fluidity, it is suitable for die-casting thin-walled, large-sized, high-precision, and complex shaped workpieces, such as electrical components and their boxes.

Magnesium alloy

Magnesium alloy is an alloy composed of magnesium as the base and other elements added. The main alloying elements include aluminum, zinc, manganese, cerium, thorium, as well as small amounts of zirconium or cadmium. The most widely used currently is magnesium aluminum alloy, followed by magnesium manganese alloy and magnesium zinc alloy. Magnesium alloys, due to their excellent casting, extrusion, cutting, and bending properties, can be widely used in the fields of automobiles, electronics, textiles, construction, and military.

The melting point of magnesium alloy is 650 ℃, which is lower than that of aluminum alloy and has good die-casting performance. The tensile strength of magnesium alloy castings is comparable to that of aluminum alloy castings, generally reaching up to 250 MPa and up to over 600 MPa.

Magnesium alloy has a low density (around 1.8g/cm3) and high strength. Magnesium alloy is the lightest metal structural material, with a specific gravity of only 1.8, which is 2/3 of aluminum and 1/4 of iron, respectively. Its specific strength is as high as 133, making it suitable as a high-strength material. The specific strength of high-strength magnesium alloys can even be comparable to titanium.

Magnesium alloy has a high elastic modulus and good seismic resistance. Within the elastic range, when subjected to impact loads, magnesium alloy absorbs half of the energy compared to aluminum alloy parts, so magnesium alloy has good seismic and noise reduction performance.

Magnesium alloy has good die-casting performance, with a minimum wall thickness of 0.5mm, suitable for manufacturing various types of automotive die-casting parts. Magnesium alloy parts have high stability, and the dimensional accuracy of die-casting parts is high, which can be used for high-precision mechanical processing.

Magnesium alloy has absolute advantages in heat dissipation compared to alloys. For radiators made of magnesium alloy and aluminum alloy materials with the same volume and shape, the heat (temperature) produced by a certain heat source is more easily transferred from the root of the heat sink to the top of magnesium alloy than aluminum alloy, and the top is more capable of reaching high temperatures.

But the coefficient of linear expansion of magnesium alloy is very large, reaching 25-26 μ M/m ℃, while aluminum alloy is 23 μ M/m ℃, brass about 20 μ M/m ℃, structural steel 12 μ M/m ℃, cast iron about 10 μ M/m ℃, rock (granite, marble, etc.) is only 5-9% μ M/m ℃, glass 5-11 μ M/m ℃. When applied to heat sources, the influence of temperature on structural dimensions must be considered.

Examples of applications of magnesium alloy: Generally, high-end and professional digital SLR cameras use magnesium alloy as the skeleton, making it sturdy, durable, and has a good tactile feel; The shell of a mobile phone or laptop; Use magnesium alloy on the casing and cooling components of computers and projectors that generate high temperatures internally; Structural components such as car steering wheel, steering bracket, brake bracket, seat frame, mirror bracket, and distribution bracket that require light weight and high strength.

According to the forming method, it is divided into two categories: deformed magnesium alloys and cast magnesium alloys.

Magnesium alloy grades are represented in the form of English letters, numbers, and letters. The first letter in English is the code for its most important alloy composition element (as specified in the table below), and the following numbers represent the average of the upper and lower limit values of its most important alloy composition element. The last English letter is the identification code used to identify different alloys with different specific constituent elements or slight differences in element content.

Common grades of magnesium alloys include AZ31B, AZ31S, AZ31T, AZ40M, AZ41M, AZ61A, AZ61M, AZ61S, AZ62M, AZ63B, AZ80A, AZ80M, AZ80S, AZ91D, AM60B, AM50A, M1C, M2M, M2S, ZK61M, ZK61S, ME20M, LZ91, LZ61, LZ121, LA141, LA191, LAZ933, LA81, LA91, LAZ931, MA18, MA21 MA14, etc.

Titanium alloy

Titanium alloy refers to various alloy metals made of titanium and other metals, with high strength, good corrosion resistance, and high heat resistance. Titanium alloy is widely used in the production of aircraft engine compressor components, frames, skins, fasteners, and landing gears. Titanium alloys are also used in structural components of rockets, missiles, and high-speed aircraft.

Titanium is an allotrope with a melting point of 1668 ℃ and a densely packed hexagonal lattice structure below 882 ℃, known as α Titanium; It exhibits a body centered cubic lattice structure above 882 ℃, known as β Titanium. By utilizing the different characteristics of the two structures of titanium mentioned above, appropriate alloying elements are added to obtain titanium alloys with different microstructures. At room temperature, titanium alloys have three types of matrix structures, which can be divided into the following three categories: α Alloy（ α+β) Alloy and β Alloy. China is represented by TA, TC, and TB respectively.

The density of titanium alloy is generally around 4.51g/cm3, which is only 60% of steel. Some high-strength titanium alloys exceed the strength of many alloy structures, so the specific strength (strength/density) of titanium alloy is much higher than that of other metal structural materials, which can produce components with high unit strength, good rigidity, and light weight.

Titanium is non-toxic, lightweight, high-strength, and has excellent biocompatibility, making it an ideal medical metal material that can be used as an implant for human body. In the United States, there are already 5 types β Titanium alloys are recommended in the medical field, namely TMZFTM (TI-12Mo - ^ Zr-2Fe), Ti-13Nb-13Zr, Timetal 21SRx (TI-15Mo-2.5Nb-0.2Si), Tiadyne 1610 (Ti-16Nb-9.5Hf), and Ti-15Mo, and are suitable for implantation in human bodies, such as artificial bones and vascular stents.

TiNi alloy has good biocompatibility, and there are quite a few medical examples utilizing its shape memory effect and superelasticity. Such as thrombus filters, spinal correction rods, dental correction wires, vascular stents, bone plates, intramedullary needles, artificial joints, contraceptives, heart repair components, miniature pumps for artificial kidneys, etc.

Titanium alloy products can be obtained through die casting and mechanical processing methods. The melting temperature of titanium alloy is very high, and the requirements for mold steel are also high. There are many methods for machining titanium alloys, mainly including turning, milling, boring, drilling, grinding, tapping, sawing, and electrical discharge machining.

The mechanical processing performance of titanium alloy is also poor. When cutting titanium alloys, the cutting force is only slightly higher than that of steel with the same hardness, but most titanium alloys have low thermal conductivity, only 1/7 of steel and 1/16 of aluminum. Therefore, the heat generated by cutting does not dissipate quickly and accumulates in the cutting area, leading to rapid wear of the tool edge, collapse, and the formation of chip deposits.