With the improvement of people's living quality,the requirements for product aesthetics and quality are also constantly increasing.More and more consumer products are made using 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 consumers'minds.

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

Therefore,an inductive summary is presented first,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 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

In terms of product structural design,weight also needs to be considered.If specific gravity is taken into account,zinc alloy has the highest density but the lowest specific strength.Titanium alloy and magnesium alloy have higher specific strength,but titanium alloy is expensive and has poor processability.Therefore,in structural components where weight and strength are to be comprehensively considered,magnesium alloy is often used.

Aluminum alloy

The material composition can be directly found on Baidu,so I won't take up space here by listing it.The density of aluminum alloy is 2.63~2.85g/cm,with high strength(σb is 110~270MPa),specific strength close to high alloy steel,specific stiffness exceeding steel,good casting performance and plastic processing performance,good electrical conductivity and thermal conductivity,good corrosion resistance and weldability.

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

Aluminum alloy exhibits the richest forms of technological application in product structure design.Common processing techniques include die-casting,extrusion molding,machining,stamping,and forging.Aluminum alloy profiles are widely used in building doors and windows,and mechanical equipment often utilizes aluminum profiles to construct frames.The casings of electronic products and fast-moving consumer goods also frequently incorporate aluminum alloy.These products have high appearance requirements,and common processes include extrusion,machining,stamping,etc.

The use of die-cast aluminum for the casings of fast-moving consumer goods is relatively rare.This is because die-cast aluminum alloys contain a high proportion of silicon(Si),which reacts directly with the chemical solution during anodizing,resulting in a poor surface finish after oxidation.Aluminum castings are commonly used for internal structural components and parts with low appearance requirements.Motorcycle engine casings,which require complex structures,light weight,and sufficient strength,are mostly made from rotary aluminum alloy die-casting as the base material.

Aluminum cast engine housing

Aluminum grade:

The 1×××series consists of pure aluminum(with an aluminum content of not less than 99.00%).The last two digits of the series designation indicate the percentage point of the minimum aluminum content.The second letter of the designation indicates the modification of the original pure aluminum.

The last two digits of the 2×××～8×××series designations have no special significance and are solely used to distinguish between different aluminum alloys within the same group.The second letter of the designation indicates the modification of the original pure aluminum.

The 2×××series refers to aluminum alloys with copper as the main alloying element.2011 is a fast-cutting alloy with good machinability and high strength.2018 and 2218 are forging alloys with good forgeability and high temperature strength.

The 3×××series refers to aluminum alloys with manganese as the main alloying element.3105 is used for building materials,colored aluminum sheets,and bottle caps.

The 4×××series refers to aluminum alloys with silicon as the main alloying element.4032 has good heat resistance and wear resistance,and a low coefficient of thermal expansion.It is used for pistons and cylinder heads.

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

The 6×××series refers to aluminum alloys with magnesium as the main alloying element and Mg2Si phase as the strengthening phase.6063 is a representative extrusion alloy with lower strength compared to 6061,but it has good extrusion properties and can be used for complex cross-sectional shapes.It has excellent corrosion resistance and surface treatment properties,and is widely used in construction,highway guardrails,high fences,vehicles,furniture,home appliances,and decorations.

The 7×××series refers to aluminum alloys 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.Coating it with a material similar to that of 7072 can improve its corrosion resistance,but at the cost of increased production costs.It is commonly used in aircraft and ski poles.

The 8×××series refers to aluminum alloys with other elements as the main alloying components

The 9×××series belongs to the spare alloy group

Aluminum alloys with a tensile strength greater than 480 MPa are referred to as high-strength aluminum alloys,primarily consisting of alloys based on Al-Cu-Mg and Al-Zn-Mg-Cu,namely 2XXX(hard aluminum alloy)and 7XXX(super-hard aluminum alloy)series alloys.The static strength of the former is slightly lower than that of the latter,but its operating temperature is higher.Due to differences in chemical composition,melting and solidification methods,processing techniques,and heat treatment regimes,the properties of alloys vary greatly.

Zinc alloy

Zinc alloys have a low melting point,good fluidity,and are easy to weld.According to the manufacturing process,they can be divided into cast zinc alloys and wrought zinc alloys.Cast zinc alloys have good fluidity and corrosion resistance,and are suitable for die-casting instruments,automotive part casings,etc.Wrought zinc alloys have excellent plasticity and ductility,and are mainly used for battery casings,printing plates,roof panels,and daily-use hardware.The production of cast alloys is much larger than that of wrought alloys,and for structural parts of fast-moving consumer goods,wrought alloys are rarely used.Therefore,the following discussion will focus solely on die-casting zinc alloys.

The density of zinc alloy is 6.3~6.7g/cm,with a tensile strengthσb of 280~440MPa.It has a low melting point,melting at 385℃,and is easy to die-cast.

Zinc alloy has the highest specific gravity among the four alloys mentioned in this article,and it also boasts the best fluidity.It exhibits excellent casting properties,enabling the die-casting of complex,thin-walled precision parts with smooth surfaces.In my designed products,the thinnest wall thickness of zinc alloy die-casting parts is only 0.4mm.

At room temperature,zinc alloy exhibits good strength.However,it is important to note that zinc alloy should not be used in working environments with high or low temperatures(below 0℃).Zinc alloy has good mechanical properties at room temperature.However,its tensile strength significantly decreases at high temperatures and its impact resistance significantly decreases at low temperatures.Zinc alloy has poor corrosion resistance.When the impurity elements lead,cadmium,and tin in the alloy composition exceed the standard,the castings will age and deform.Zinc alloy die-castings have aging effects,which means that their strength naturally decreases over time and they become brittle.This is why many people roast that when replacing zinc alloy faucets,they often break brittlely,leaving the threaded part of the faucet stuck in the water pipe and unable to be removed.Therefore,Fang Gong still recommends that everyone choose copper faucets for decoration rather than zinc alloy ones.

Currently,there are two major standard series of alloys used for castings internationally:ZAMAK alloys and ZA series alloys.The ZAMAK alloys used include ZAMAK 2,ZAMAK 3,ZAMAK 5,and ZAMAK 7(for simplicity,these alloys are collectively referred to as No.2,No.3,No.5,and No.7 alloys).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,due to their special melting requirements,can only be used for cold chamber die casting.ZA-35 is generally used for gravity casting.The development of ZAMAK alloys precedes that of the ZA series alloys,and they are mainly used for pressure casting.The most widely used alloy is No.3 zinc alloy.

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

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

ZAMAK 5:Good fluidity and excellent mechanical properties.It is applied to castings that require a certain level of mechanical strength,such as automotive parts,electromechanical components,mechanical parts,and electrical components.

ZA8:It possesses good impact strength and dimensional stability,but exhibits poor fluidity.It is suitable for die-casting small-sized workpieces that require high precision and mechanical strength,such as electrical components.

Superloy:With the best fluidity,it is applied to die-casting workpieces with thin walls,large dimensions,high precision,and complex shapes,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 alloy elements include aluminum,zinc,manganese,cerium,thorium,and a small amount of zirconium or cadmium.Currently,magnesium-aluminum alloy is the most widely used,followed by magnesium-manganese alloy and magnesium-zinc alloy.Due to its excellent casting,extrusion,cutting,and bending properties,magnesium alloy can be widely applied in the automotive,electronics,textile,construction,and military fields.

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

Magnesium alloy has a low density(around 1.8g/cm3)and high strength.It is the lightest metallic structural material,with a specific gravity of only 1.8,which is 2/3 of aluminum and 1/4 of iron.Its specific strength is as high as 133,making it suitable for use as a high-strength material.The specific strength of high-strength magnesium alloy can even rival that of titanium.

Magnesium alloys have a high elastic modulus and good shock absorption properties.Within the elastic range,when subjected to impact load,magnesium alloys absorb half as much energy as aluminum alloy components,thus demonstrating excellent shock resistance and noise reduction performance.

Magnesium alloy exhibits excellent die-casting formability,with die-casting parts achieving a minimum wall thickness of 0.5mm,making it suitable for manufacturing various automotive die-casting components.Magnesium alloy parts exhibit high stability,and die-casting components exhibit high dimensional accuracy in casting processing,allowing for high-precision machining.

Compared to other alloys,magnesium alloys have an absolute advantage in heat dissipation.For radiators made of magnesium alloy and aluminum alloy with the same volume and shape,the heat(temperature)generated by a certain heat source is more likely to be transferred from the root to the top of the radiator in magnesium alloy than in aluminum alloy,and the top is more likely to reach high temperatures.

However,magnesium alloy has a high linear expansion coefficient,reaching 25-26μm/m℃,compared to 23μm/m℃for aluminum alloy,about 20μm/m℃for brass,12μm/m℃for structural steel,about 10μm/m℃for cast iron,and only 5-9μm/m℃for rocks(such as granite and marble),and 5-11μm/m℃for glass.When applied at the heat source,the impact of temperature on structural dimensions must be considered.

Examples of magnesium alloy applications:Generally,mid-to-high-end and professional digital SLR cameras use magnesium alloy as the frame,making them sturdy,durable,and comfortable to handle;cases for mobile phones and laptops;magnesium alloy is used in the casings and cooling components of computers and projectors that generate high internal temperatures;structural components such as car steering wheels,steering brackets,brake brackets,seat frames,mirror brackets,and distribution brackets that require light weight and high strength.

According to the forming method,magnesium alloys can be divided into two categories:wrought magnesium alloys and cast magnesium alloys.

The magnesium alloy grades are denoted in the format of English letter+number+English letter.The initial English letter represents the code of its primary alloy constituent element(as specified in the table below),the subsequent number indicates the average of the upper and lower limits of its primary alloy constituent element,and the final English letter serves as an identification code to distinguish between different alloys with distinct specific constituent elements or slight variations 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 a variety of alloy metals made from titanium and other metals,which exhibit high strength,good corrosion resistance,and high heat resistance.Titanium alloys are widely used in the production of aircraft engine compressor components,frames,skins,fasteners,landing gear,etc.Titanium alloys are also applied in structural components of rockets,missiles,and high-speed aircraft.

Titanium is an allotrope with a melting point of 1668℃.Below 882℃,it adopts a hexagonal close-packed lattice structure,known asαtitanium;above 882℃,it adopts a body-centered cubic lattice structure,known asβtitanium.By utilizing the different characteristics of these two structures of titanium,appropriate alloying elements are added to obtain titanium alloys with different microstructures.At room temperature,titanium alloys have three matrix microstructures,which are divided into the following three categories:αalloy,(α+β)alloy,andβalloy.These are represented by TA,TC,and TB in China,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.Therefore,the specific strength(strength/density)of titanium alloy is much higher than that of other metal structural materials,allowing the production of components with high unit strength,good rigidity,and light weight.

Titanium is non-toxic,lightweight,high in strength,and possesses excellent biocompatibility,making it an ideal medical metal material for use as implants in the human body.In the United States,five types ofβtitanium alloys have been recommended for use 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,which are suitable for implantation in the human body as implants such as artificial bones and vascular stents.

TiNi alloy exhibits excellent biocompatibility,and there are numerous medical applications that utilize its shape memory effect and superelasticity.These include thrombus filters,spinal orthopedic rods,orthodontic wires,vascular stents,bone plates,intramedullary nails,artificial joints,contraceptives,heart repair components,and micro-pumps for artificial kidneys.

Titanium alloy products can be obtained through die-casting and machining methods.Titanium alloy has a high melting temperature,thus requiring high-quality mold steel.There are many methods for machining titanium alloy,mainly including:turning,milling,boring,drilling,grinding,threading,sawing,and electric discharge machining(EDM),etc.

The machinability of titanium alloys is also poor.During the cutting process of titanium alloys,the cutting force is only slightly higher than that of steel with the same hardness.However,most titanium alloys have very low thermal conductivity,only 1/7 of steel and 1/16 of aluminum.Therefore,the heat generated during cutting does not dissipate quickly and accumulates in the cutting area,leading to rapid wear of the tool blade edge,chipping,and the formation of built-up edge.