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

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

For consumer products, common alloy materials include aluminum alloy, zinc alloy and magnesium alloy. Titanium alloys are commonly used in medical field due to their good biological compatibility. Fang Gong comes here to compare the characteristics of these alloy materials.

Therefore, the inductive summary is put forward, as shown in the following performance comparison table.

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

Strength and hardness comparison

However, in terms of product structure design, weight also needs to be considered. If the specific gravity is taken into account, the specific strength of zinc alloy is the minimum because of its maximum density. Titanium alloys and magnesium alloys have high specific strength, but titanium alloys are expensive and have poor workability. Therefore, magnesium alloys are mostly used in structural parts that need to consider weight and strength comprehensively.

The ingredients of the materials can be found directly from Du Niang. 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), the specific strength is close to that of high alloy steel, and the specific stiffness is higher than that of steel. It has good casting performance, plastic processing performance, good electrical conductivity, thermal conductivity, good corrosion resistance and weldability.

The fluidity of die-casting aluminum alloy is relatively good, and the melting point is 660 ℃.

Aluminum alloy is also the most widely used process in product structure design. Common processing technologies include die casting, extrusion molding, machining, stamping and forging. Aluminum alloy profiles are widely used for building doors and windows, and aluminum profiles are also commonly used for building frames for mechanical equipment. The shells of electronic products and FMCG products are also made of aluminum alloy. Such products have high appearance requirements. The common processes are extrusion, machining, stamping, etc.

Die cast aluminum is less used for the housing of FMCG. Because die cast aluminum alloy contains high content of Si, it directly reacts with liquid medicine during anodizing, and the surface effect is poor after oxidation. Aluminum castings are often used for internal structural parts and parts with low requirements for appearance. Motorcycle engine housings require complex structures, light weight and sufficient strength. Most of the rotary aluminum alloy die castings are used as blanks.

one ××× Series: pure aluminum (aluminum content is not less than 99.00%), and the last two digits of the series grade are expressed as percentage points of the lowest aluminum content. The second letter of the grade indicates the modification of the original pure aluminum.

two ×××～ eight ××× The last two digits of the series designation have no special significance and are only used to distinguish different aluminum alloys in the same group. The second letter of the grade indicates the modification of the original pure aluminum.

two ××× Series: aluminum alloy with copper as the main alloy element. 2011 fast cutting alloy has good machinability and high strength. 2018 2218 alloy for forging, with good forgeability and high high temperature strength.

three ××× Series: aluminum alloy with manganese as the main alloy element. 3105 3105 building materials, colored aluminum plates, bottle caps.

four ××× Series: aluminum alloy with silicon as the main alloy element. 4032 Good heat resistance, friction resistance and elimination resistance, small thermal expansion coefficient. Piston and cylinder head.

five ××× Series: aluminum alloy with magnesium as the main alloy element. 5052 is the most representative alloy of medium strength, including general sheet metal, ships, vehicles, buildings, bottle caps and honeycomb panels.

six ××× The series are aluminum alloys with magnesium as the main alloy element and Mg2Si phase as the strengthening phase. 6063 is a representative extrusion alloy with low strength and good extrudability compared with 6061. It can be used as a shape material with complex section shapes. It has good corrosion resistance and surface treatment properties, such as buildings, highway guardrails, high fences, vehicles, furniture, household appliances and decorations.

seven ××× Series: aluminum alloy with zinc as the main alloy element. 7075 aluminum alloy is one of the alloys with the highest strength, but its corrosion resistance is poor. It can improve its corrosion resistance with 7072 covering leather, but its cost is increased. Aircraft, ski poles.

eight ××× Series: aluminum alloy with other elements as main alloy elements

nine ××× Series: spare alloy group

Aluminum alloys with tensile strength greater than 480MPa are called high-strength aluminum alloys, mainly based on Al Cu Mg and Al Zn Mg Cu, namely 2XXX (duralumin alloys) and 7XXX (super duralumin alloys) series alloys. The static strength of the former is slightly lower than the latter, but the service temperature is higher than the latter. Due to the different chemical composition, melting and solidification methods, processing technologies and heat treatment systems, the properties of alloys vary greatly.

Zinc alloy has low melting point, good fluidity and easy welding. According to the manufacturing process, it can be divided into cast zinc alloy and deformed zinc alloy. Cast zinc alloy has good fluidity and corrosion resistance, and is suitable for die-casting instruments, automobile parts, shells, etc. Deformed zinc alloy has good plasticity and ductility, and is mainly used as battery shell, printed board, roof panel and daily hardware. The output of casting alloy is much higher than that of wrought alloy, and wrought alloy is rarely used for structural parts of FMCG. Therefore, the following is only for die-casting zinc alloy.

Zinc alloy density is 6.3~6.7g/cm, tensile strength σ B 280~440MPa, low melting point, melting at 385 ℃, easy to die cast.

Zinc alloy has a large proportion, which is the largest proportion among the four alloys described in this paper. It also has the best fluidity and has good casting performance. It can die cast precision parts with complex shapes and thin walls, and the casting surface is smooth. Among the products I designed, the thinnest thickness of zinc alloy die castings is only 0.4mm.

At room temperature, the strength of zinc alloy is good. It should be noted that zinc alloy should not be used in the working environment of high temperature and low temperature (below 0 ℃), and zinc alloy has good mechanical properties at room temperature. However, the tensile strength at high temperature and the impact property at low temperature decreased significantly. Zinc alloy has poor corrosion resistance. When the impurity elements lead, cadmium and tin in the alloy composition exceed the standard, the casting will be aged and deformed. Zinc alloy die castings 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 the zinc alloy faucet, brittle fracture often occurs, resulting in the thread part of the faucet remaining in the water pipe. Therefore, Fang Gong suggests that you should choose copper faucets rather than zinc alloy ones when decorating.

At present, there are two kinds of standard series used for castings in the world, one is ZAMAK alloy, the other is ZA series alloy. ZAMAK alloys used include ZAMAK 2, ZAMAK 3, ZAMAK 5 and ZAMAK 7. (For simplicity, the above alloys are collectively referred to as No. 2, No. 3, No. 5 and No. 7 alloys). ZA series includes ZA-8, ZA-12, ZA-27 and ZA-35. ZA-8 is mainly used for hot chamber die casting, and 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. ZAMAK alloy is developed prior to ZA series alloy and is mainly used for die casting. The most widely used is No. 3 zinc alloy.

ZAMAK 2: It is used for mechanical parts with special requirements for mechanical properties, high requirements for hardness, good wear resistance and general requirements for dimensional accuracy.

ZAMAK 3: Good fluidity and mechanical properties. It is applied to castings with low requirements on mechanical strength, such as toys, lamps, decorations and some electrical parts.

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

ZA8: It has good impact strength and dimensional stability, but poor fluidity. It is used for die-casting workpieces with small size, high precision and mechanical strength requirements, such as electrical parts.

Superloy: With the best fluidity, it is applied to die-casting workpieces with thin wall, large size, high precision and complex shape, such as electrical components and their boxes.

Magnesium alloy is an alloy composed of magnesium and other elements. The main alloy elements are aluminum, zinc, manganese, cerium, thorium and a small amount of zirconium or cadmium. At present, magnesium aluminum alloy is the most widely used, followed by magnesium manganese alloy and magnesium zinc alloy. Magnesium alloys can be widely used in automotive, electronic, textile, construction and military fields because of their excellent casting, extrusion, cutting and bending properties.

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

Magnesium alloy has low density (about 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 up to 133, which makes magnesium alloy can be used as a high-strength material. The specific strength of high-strength magnesium alloys can even be comparable to that of titanium.

Magnesium alloy has large elastic modulus and good shock absorption. Within the elastic range, when magnesium alloy is subjected to impact load, it absorbs more than half of the energy than aluminum alloy parts. Therefore, magnesium alloy has good seismic and noise reduction performance.

Magnesium alloy has good die-casting formability, and the minimum wall thickness of die-casting parts can reach 0.5mm, which is suitable for manufacturing various automotive die castings. Magnesium alloy parts have high stability, and die-casting parts have high dimensional accuracy for casting processing, which can be machined with high precision.

The heat dissipation of magnesium alloy is absolutely superior to that of alloy. For the radiators made of magnesium alloy and aluminum alloy with the same volume and shape, the heat (temperature) produced by a heat source of magnesium alloy is easier to transfer from the root of the radiator to the top than that of aluminum alloy, and the top is easier to reach high temperature.

However, the linear expansion coefficient of magnesium alloy is 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℃。 The effect of temperature on the structure size must be considered when it is applied at the heat source.

Application examples of magnesium alloy: generally, high-end and professional digital SLR cameras use magnesium alloy as the skeleton to make them durable and feel good; Mobile phone and laptop shell; Use magnesium alloy on the shell and heat dissipation parts of computers and projectors that generate high temperature inside; Automobile steering wheel, steering bracket, brake bracket, seat frame, mirror bracket, distribution bracket and other structural parts that require light weight and high strength.

It can be divided into wrought magnesium alloy and cast magnesium alloy according to the forming method.

Magnesium alloy grades are expressed in the form of English letters+numbers+English letters. The English letters in front are the codes of the most important alloy constituent elements (element codes are specified in the table below), and the numbers behind represent the average of the upper and lower limit values of the most important alloy constituent elements. The last English letter is the identification code, which is used to identify different alloys with different specific constituent elements or slightly different element contents.

Common magnesium alloy grades 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 refers to a variety of alloy metals made of titanium and other metals, with high strength, good corrosion resistance and high heat resistance. Titanium alloys are widely used in the manufacture of aircraft engine compressor components, frames, skins, fasteners and landing gear. Titanium alloys are also used in structural parts of rockets, missiles and high-speed aircraft.

Titanium is an allotrope with a melting point of 1668 ℃ and a close packed hexagonal lattice structure below 882 ℃, which is called α Titanium; It has a body centered cubic lattice structure above 882 ℃, which is called β Titanium. Taking advantage of the different characteristics of the above two structures of titanium, appropriate alloy elements are added to obtain titanium alloys with different structures. At room temperature, titanium alloys have three kinds of matrix structures, and titanium alloys are also 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 about 4.51g/cm3, which is only 60% of that of steel. Some high-strength titanium alloys exceed the strength of many alloy structural steels. Therefore, the specific strength (strength/density) of titanium alloys is far greater than that of other metal structural materials, which can produce parts with high unit strength, good rigidity and light weight.

Titanium is non-toxic, light, high strength and has excellent biocompatibility. It is a very ideal medical metal material, which can be used as an implant for human body. In the United States, there are five β Titanium alloys have been recommended to 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, which are suitable for implanting into human bodies as implants, such as artificial bones, vascular stents, etc.

TiNi alloy has good biocompatibility, and there are many medical examples using its shape memory effect and hyperelasticity. Such as thrombus filter, spinal orthopedic rod, dental orthopedic wire, vascular stent, bone plate, intramedullary needle, artificial joint, contraceptive device, heart repair element, artificial kidney micro pump, etc.

Titanium alloy products can be obtained by die casting and machining. The melting temperature of titanium alloy is very high, and the requirements for die steel are also high. There are many ways to machine titanium alloys, including turning, milling, boring, drilling, grinding, tapping, sawing, EDM, etc.

The machinability of titanium alloy is also poor. During titanium alloy cutting, the cutting force is only slightly higher than that of steel with the same hardness, but most titanium alloys have very low thermal conductivity, which is only 1/7 of that of steel and 1/16 of that of aluminum. Therefore, the heat generated by cutting will not dissipate rapidly and will gather in the cutting area, resulting in rapid wear, collapse and formation of chip accretion on the tool edge.