Amorphous alloy is the general name of materials used in iPhone, in which amorphous refers to amorphous and alloy refers to alloy. However, due to the difficulty in production and high technological requirements, this material can not be used for the shell of iPhone, but only for the SIM card holder of iPhone. This part is produced by American LiquidMetal Company (the origin of the name liquid metal), and Mr. Zhang may not have touched it.
(take the card needle)
This is a real amorphous metal body. Before contact, many people mistakenly think that liquid metal is like this:
Or, like this:
Oh, no, it should be like this:
Some people even said this after seeing the news that Apple used liquid metal:
This ..... brain hole is too big to be blocked completely. ...
So I'm here to end this.
main body
To talk about liquid metal, we must first talk about ordinary metal:
As a good boy who has read junior high school, we know that metal is connected by metal bonds, which is described by the teacher as:
Positive ions surrounded by an ocean of electrons.
That is, metal cations are immersed in the ocean of free electrons.
Metal bonding will affect the following characteristics of metals:
difficulty
melting point
strong
hard
Germinable
electric
conductive
Among them, for daily use, we mainly pay attention to:
difficulty
strong
hard
Germinable
The rest, except for special purposes, will not have much influence in general life.
difficulty
Hardness is described as the ability of a material to resist permanent damage (puncture, defect). To put it bluntly, your mobile phone fell to the ground with a bang, and when it was picked up, there were no scratches on the shell.
One kind of injury is also mentioned by junior high school teachers (junior high school teachers are so big ...), which can be divided into elastic deformation and plastic deformation.
Then think about it, why are these two differences caused by the same force?
Junior high school teachers don't work at this time, because junior high school knowledge can only tell you that when the force exceeds the elastic limit of the material, the object will be plastically deformed. So, why?
The omnipotent university teacher appeared, the university teacher said, because the atom was derailed.
Forgive me for not discovering atoms ...
Everyone should have done it seriously, such as the following:
Well, it's very regular, but under the action of external force, the "Wang" on it. Eight eggs appeared, and everyone got separated. ...
Seriously, this is called atomic permanent displacement, so why does the material change its nature and shape after displacement?
Next, we should introduce a concept:
crystallinity
Sorry, I'm not sure what this is called in Chinese. This is called crystallinity (thank you @). ...
What is this? In fact, it is the form of atomic arrangement in elements. We can imagine that if we enlarge the metal, it won't be a mess. This is its natural attribute, that is, it has a distinct lattice structure. However, not all objects have this distinct lattice structure, such as glass, ceramics and other ceramic (inorganic nonmetal) materials or polymer (organic polymer) materials.
So, there will be three types of materials:
Crystalline crystal
Semicrystalline
shapeless
When you see amorphous at this time, you should know what kind of liquid metal amorphous alloy belongs to, right?
Back to the previous crystallinity, why mention this crystallinity, because it determines the order of atomic arrangement, and according to common sense of life, we know that the more orderly a room is, the easier it is to make it chaotic.
This is why matter always tends to change from order to disorder and from high energy to low energy.
In order to better understand, metals used as crystals can be divided into the following three types in the formation of atomic crystals (@ jingjingjingjingjingjingjing):
body-centered cubic
Face centered cubic
Hexagonal tight packing (HCP)
It's boring. Well, I'm bored, too, especially the pronunciation of the last one. ...
First, imagine it in your mind according to the picture. Don't just look at a picture. Try to imagine what will happen when a large number of identical structures are spliced together. Then I'll explain it separately:
body-centered cubic
Because it is a cube with an atom as the center, after many similar structures are combined, there will be a lot of atomic overlap (should be translated as overlap), because each atom can be used as the center of eight surrounding atoms. So! The stress of each atom in all directions is uniform, so it needs more force to make it plastically deform. So the hardness is very high (but not higher than that of ceramics, for reasons to be explained later). It is also strong, but this leads to the metal ductility of this structure is not very strong, which belongs to the middle level among the three structures.
The main material of this structure is steel (containing iron). Why should I use English? Because there will be a sign of steel in the back.
Face centered cubic
As you can imagine, because there is no overlapping structure in BCC, the internal force is uneven. Internal contradictions are easy to disintegrate when they are expressed. Also led to a large number of slip surfaces (mentioned in Zhihu, translated into slip surfaces), as follows. Therefore, it has lower hardness and toughness than BCC, but conversely, it has good plasticity and is suitable for molding.
The main material of this structure is aluminum (al for short).
By remembering the classification of these two main materials, we can remember the general properties of BCC and FCC structures.
Hexagonal tight packing (HCP)
This is very special. The middle layer has nothing to do with the upper and lower layers. The upper and lower layers are FCC and the middle is BCC, so it has the hardness and toughness of BCC. Do you think it combines all the advantages of BCC and FCC? You really think too much ... if there is, then we can build Iron Man together ... Its disadvantage is that it is lower than BCC, so it can be described as brittle.
* just mentioned a slip surface, this thing is defined as follows:
The slip surface is essentially the path of least resistance, through which atoms can move to compensate the applied load and force.
To put it bluntly, it is a slippery surface, and then the tortoise. Eggs, oh, no, atoms can run from here to there under pressure.
The more this surface exists, the easier it is for atoms to move, the easier it is for atoms to move and the softer the material is.
Then, we began to discuss a slightly macroscopic structure than atoms:
Five grains (fine, wrong, evil input method, five grains)
Repeat the basic crystal unit or unit cell as shown in the figure.
This thing is crystal particles:
These lines are formed like this, just like mixing the base. At first, two atoms thought it was appropriate, and then they got together, which is normal. Then they meet the third one, which is good. When three people are together, it is a threesome. Then they walked and saw the fourth person, naturally. As the number of people increases, it will gradually become 5P, 6P, 7P…… ... ...
However, with the increase of the number of people, everyone likes different postures and angles (arrangement or orientation), some like up and down, some like back and forth, and some like 69. All kinds of postures are screwed together to form a polycrystal. But because everyone is the same thing, except some people, the main bonding point (chemical bond) and direction (bond angle) are basically the same, which ensures that the crystal structure basically keeps rotating in three directions.
So I came up with something like this:
This is the incestuous society ... and then different incestuous societies, big and small (big and small), meet at the grain boundary because of external forces and internal forces, and once they are together, incest ... so it forms the appearance shown in the above picture.
Because after all, everyone has different tastes, so there will still be a little inappropriate, so there is such a dislocation:
Of course, none of this matters. I'm just saying.
have a rest
We have described the following points above:
Three different crystal structures have different properties;
The structure inside the metal can be reorganized (break up together and then change partners);
The same metal also has different crystal structure, grain size and dislocation.
Next, discuss some alloys and inorganic nonmetals:
Alloys are divided into:
Ferroalloys (including ferroalloys)
Non-ferrous alloy (iron-free)
Among them, the application of ferroalloy in iPhone is steel; The application of non-ferrous alloy in iPhone is aluminum.
Steel is divided into low/medium/high carbon steel:
low-carbon steel
The carbon content is less than 0.20%
medium carbon steel
The carbon content is between 0.20% and 0.50%.
high-carbon steel
The carbon content is 0.50% ~ 65438 0.0%
Ultra-high carbon steel (cast steel)
The carbon content is 1.0% ~ 2.0%
Cast iron (cast iron)
The carbon content exceeds 2.0%
Here we know that carbon, that is, carbon, can be converted into Fe3C when heated with iron Fe. This thing is a very special intermetallic compound with high hardness, but basically no plasticity. After mixing with iron, the original properties of iron can be greatly changed, which is reflected in the higher the carbon content, the higher the hardness of steel, but the more brittle the texture.
The following is the way to interpret steel:
For example, 10 18 steel, the first two 10XX, just tell us what elements are in it (steel can add carbon or chromium to increase hardness and corrosion resistance, copper can increase machinability, manganese can reduce brittleness, molybdenum can stabilize carbide and prevent grain growth, nickel can increase toughness and corrosion resistance, vanadium.
The last two digits XX 18 tell us the carbon content. For example, 18 is 0. 18% carbon.
I took a shower here and then came back to read a page on the computer and closed it ... Fortunately, it was saved ... scared my father to death ...)
Add a little knowledge:
There are three kinds of stainless steel:
Ferrite (ferritic stainless steel)-contains a lot of chromium (chromium), so that it will not become austenite (austenite), with low price and good oxidation resistance.
Austenite (austenitic stainless steel)-contains nickel and has high toughness, high plasticity and low strength.
Martensite (martensitic stainless steel, thank you @ Wen Zhiheng)-the chromium content is lower than that of ferrite, and it is the hardest steel that can be made by heterogeneous phase (don't ask me what phase means ... it can also be said to be a simple mixture or a simple substance with a uniform and definable structure and known chemical composition, such as air and ice).
Then introduce non-ferrous alloys, taking aluminum as an example:
Corrosion resistance (corrosion resistance)
Easy to manufacture (easy to cast)
High electrical and thermal properties.
Light weight (light, just compare iPhone 4/4S with iPhone 5s)
Strength at high temperature (temperature hardly affects strength)
Beauty (beauty, iron and everything)
Please combine the crystal structure of al to understand the above characteristics.
Then, in Mr. Zhang Yi's answer, he mentioned:
I tell you clearly that the iPhone 5 shell is not liquid metal, but made of AL6063 T6 aluminum alloy (aluminum extrusion) produced by Jinqiao Aluminum. The cavity and shape are processed by CNC machine tools, then the upper, middle and lower metal blocks are connected by injection molding, and then processed by CNC machine tools, and the anode dyeing is omitted in the middle (for fear of being accused of leaking secrets) to process the shell.
Can I say that the liquid metal anode dyeing process is not good? In fact, even the anodic dyeing of AL7075 has problems.
What do the words AL6063 and AL7075 mean?
Unlike steel, aluminum is pronounced
X-X-XX
The first number, similar to steel, is used to define the kind of elements added:
1xxxx–99% aluminum is basically pure aluminum.
2xxx–copper plus copper
3xxx–manganese acceleration
4xxx-–silicon plus silicon
5xxx–magnesium plus magnesium
6 XXX-–magnesium and magnesium alloys; Silicon, this is silicon and magnesium.
7xxx–Zinc
8xxx–Other elements
The second number indicates the control requirements for the limit content of elements or impurities in the alloy. If the second number is 0, it means that there is no special control requirement for the limit of impurities. If it is 1 ~ 9, the larger the number, the more control requirements, generally 0.
Unlike steel, the last two digits are used to indicate the number of this aluminum in the same type.
So we know that the aluminum used for iPhone 5 is Si-Mg-Al alloy. Why use 6063 instead of 606 1 (higher strength), because 6063 is more suitable for polishing after extrusion and anodic oxidation.
After introducing materials, let's talk about strain and stress.
Strain (? )
Deformation response of materials to external force or load
Refers to the deformation response of materials to external forces, which are compensated by atoms by destroying crystal structure.
Imagine that when two people (of course, it can also be three, four or more people) live together, the bed and mattress under you are very harmonious. ...
According to different postures, strain has different manifestations:
Compression compression
stretching
shear deformation
Think about it. It's so vivid ...
Stress (σ)
How the material distributes the applied load internally.
Please pay more attention to this word, internally, internally.
That is, when you and your girlfriend achieve great harmony in life, the springs in the mattress disperse the force to all parts.
Why should we emphasize this point? Let's talk about it after orgasm.
Under normal circumstances, strain and stress are linear:
But until the external force is constantly applied ...
You will reach a point called the yield point, which is the point where the atoms in the material begin to move from the original position to the new position. (that is, the focus of the two lines in the above picture)
Then continue to put pressure on it, and it becomes this withered sample:
It's ... it's an orgasm ...
This is called ultimate tensile strength (UTS) ... After crossing this mountain, things will break. ...
This is a variety of data of several common materials. ...
Among them, aluminum still uses 606 1 with strength higher than 6063.
Ok, a lot of nonsense, let's formally talk about what amorphous metal (commonly known as liquid metal) is. ...
For the last time, really, I swear
Let's learn how to change the properties of metals:
Children who have seen Wolverine should remember that there are a lot of ultra-high density alloys (like Captain America's shield) in Wolverine's body. In the movie, there is such a dialogue:
The general said: Do you know what is the most difficult thing to inject metal into your body?
The general himself replied: it is to keep the ultra-high density alloy in a liquid state (injecting liquid paint into Wolverine's body ... my God ... no wonder Wolverine was so miserable at that time, and then he was so heartbroken that he wanted to go to the general)
Who wiped my ass!
This process of melting metal is a way for us to change metal:
heat treatment
Controlled heating and cooling of materials in order to change their structure and properties.
Mastered these two elements, you can control the metal, everyone is Wan Ciwang:
temperature
cooling velocity
How?
"step by step"
We know that metals have a unique lattice structure and tend to form naturally.
When an alloy is synthesized, atoms as solutes dissolve into atoms as solvents, like this:
Then heating continuously, the metal will dissolve and become molten.
At this time, if the metal is allowed to cool down (I didn't say the rate yo), the metal atoms will lose energy and start to form solids.
How is it formed? Low-energy metal atoms that lose energy will start to rearrange (after the climax, the energy will be low, and then they will find a new partner and change positions). This time is called nucleation point.
Then, find a good partner, and the atoms that change their attitude begin to form particles again. As for how to form them, please see the front ... specifically, the grain size becomes larger in all aspects.
The grains begin to meet other grains at grain boundaries and gradually form new metals.
There is a pit ahead. The cooling rate and temperature of this metal are important elements to change the properties of the metal, right? So, how much is it?
full annealing
orthonormal
extinguish
I'll leave this hole first and talk about it later.
Heat treatment is a method to change the grain size of metal, but this heating is not the only method. Why? Because heating provides energy for metal atoms, doesn't it? As long as we can provide energy, can we change it?
So, if I keep going to Bai Wan to get a metal bar (please don't get me wrong), it will break, won't it?
This is the second one:
Mechanical hardening
Plastic deformation changes the grain size.
Specific process:
You need a hard stick. ...
Bai Wan, it. ...
On the other hand, Bai Wan, it ...
Repeat (please don't do this ... it's painful)
This bending always causes large particles to be broken into small particles.
As a result, the internal stress increases sharply in the grain boundary region (now do you know why the internal stress is repeated internally? )
Stress and strain are linear to some extent (remember the picture? )
With the increase of strain, the stress increases, then the number of grains increases, the size decreases, and the overall ductility of metal materials decreases (you can try to break the paper clip, and the fracture will be hard after breaking).
If pragmatic deformation continues at this time, the material will break.
At this time, if we heat the material before the ninth step, the thermal energy will provide enough energy for the grains to form new grains, then the internal stress can be reduced, the machinability can be improved, and the material will not break, but it will be subdivided into small enough.
So this time back to the question of heating rate:
Recall the effect of grain size on metal properties:
Smaller particles = higher hardness. Strength, low ductility
Larger particles = lower hardness. Strength, higher ductility
Now back to the three rates mentioned above, different rates will have completely different results for the same material:
Complete annealing (slowest)
The material is heated above its phase transition temperature and slowly cooled in the furnace.
After the material is melted, it is cooled in an oven (for example, for AL606 1-O, it can be reduced from 940 degrees Celsius to 10 degrees every three hours), which provides enough heat and time for atoms to form crystal grains, thus forming large and neat crystal grains.
The produced products have enough toughness.
Standardization (intermediate)
The material is heated above the phase transition temperature and then cooled in still air.
It is cooled in the air, not actively heated, not actively cooled.
The left is completely annealed and the right is normalized.
Quenching (fastest)
"Rapid" cooling of materials. Using various materials as quenching media, heat is removed from the materials at an accelerated speed.
It can be placed in some low-temperature media, such as water, oil, metal, sand, polymer compounds and so on.
This is martensite (the hardest steel at present, it can be seen that there is basically no grain structure)
Well, at this point, we probably know that the higher the temperature of the metal, the faster the cooling rate of the metal, the smaller the grain size and the less the grain structure of the metal, which directly affects the higher the hardness and the lower the ductility, and vice versa.
So what is liquid metal?
Amorphous alloy, amorphous alloy, that is to say, it has no crystal structure and no grains at all, so its ductility is low, but on the contrary, its hardness is extremely high, similar to glass. So why not use glass? Because glass has basically no ductility ... Although ... the ductility of amorphous alloys is very low, it still retains some properties of metals, including some ductility, but it is much lower than that of conventional crystalline alloys.
This material is very suitable for mobile phone case. It not only has ultra-high hardness (2.5 times that of titanium alloy and 0.5 times that of 65438+ stainless steel), but also has certain ductility, and it will not be broken by a little external force like glass, and it maintains a very light weight. But the problem is that the cost is too high and the process requirements are high:
This is a simple description of Zhang Mao:
Either casting and quenching directly, or forming in supercooled liquid phase region.
To explain, we mentioned earlier that martensite is quenched and extremely cold, so suppose what happens if the metal is kept at a high temperature above 900 degrees and cooled instantly? Then we can get an alloy composed of disordered atoms, which will be much harder than steel.
The second question is: in the face of a large piece of metal, how to make the metal cool evenly and quickly both inside and outside? That's why Apple hasn't used liquid metal in the case of iPhone and iPad yet.
In order to achieve this condition, Apple even wants to achieve the ultimate cooling time through anti-gravity casting:
Of course, the ideal is always beautiful and the reality is always cruel. Now we can only see the existence of liquid metal on the iPhone's card-fetching pin. I hope that one day, no matter who they are, they can find a relatively simple casting method. At that time, maybe 2 1 century will not be the century of titanium, but the century of liquid metal.