The sinking of the Titanic was a tragedy that showed the limitations of the technology of the time, and explores the possibility that understanding and applying the phenomenon of metal diffusion could prevent similar tragedies in the future.
On April 10, 1912, the ship sailed from the port of Southampton, England, when it struck an iceberg and sank with its hull split in two. This tragedy, in which 1,500 of the ship’s 2,200 passengers sank to the bottom of the ocean, is the famous Titanic. The Titanic was considered the pinnacle of technology at the time, and was dubbed the “unsinkable” ship. But despite its reputation, the Titanic sank on its maiden voyage. While people at the time may have thought it was a simple accident, the sinking of the Titanic was a stark reminder of the limitations of modern technology.
What would have happened if the Titanic’s hull had been stronger? Perhaps the tragedy of hitting an iceberg and sinking would have been avoided, and we wouldn’t have the movie Titanic starring Leonardo DiCaprio. The movie remains a classic of the century to this day and has touched many people deeply. Without the sinking of the Titanic, we wouldn’t have the range of emotions and memories that the movie evoked. It’s a great example of how a piece of history can influence art and culture.
But if the people who built the Titanic’s hull had known about metal “diffusion,” the ship might not have sunk. If they understood diffusion and were able to control the strength of the metal appropriately, the Titanic tragedy as we know it today would not have happened.
When we think of “diffusion,” we often think of the way a perfume smell spreads through the air, or the way a drop of ink mixes in water. In fact, some dictionaries describe diffusion as the spreading of molecules in a gas or liquid from a place of higher concentration or density to a place of lower concentration or density due to differences in density or concentration. While this description provides an important foundation for understanding the phenomenon of diffusion, diffusion in solids such as metals has a more complex mechanism. The idea of diffusion occurring in a solid that is seemingly solid and doesn’t flow like water or air may seem a little strange. But diffusion in metals occurs frequently, even if it’s not as fast as you can see, and it’s an important factor in the properties and performance of the metal products we use.
The steel plates in your car’s motor and gears, and the hulls of airplanes and ships are made up of alloys. Many of the metals we recognize, even the stainless steel appliances in every kitchen in the country, are made up of alloys rather than pure metals to increase their strength. One of the most popular methods used to create these alloys is called “diffusion” of metals. Diffusion of metals is the movement of atoms across the interface of two dissimilar materials when they come into contact. In this process, new alloys are formed, and the properties of the metals are changed and strengthened.
There are two main mechanisms of metal diffusion. They are vacancy diffusion and interstitial diffusion. First, let’s take a look at vacancy diffusion. Metals are aggregates of atoms connected together by interatomic metallic bonds. No matter how smooth and full a metal looks, there are voids, or empty spaces. Vacancy diffusion means that atoms diffuse through these voids. When one metal atom moves into the vacant space next to it, the space becomes empty again and the neighboring atoms move into the vacant space, and so on. This process is relatively slow, but it results in significant changes to the microstructure of the metal.
The second mechanism, interstitial diffusion, is a phenomenon often found in metals with large differences in atom size, unlike vacancy diffusion. It involves the movement of smaller atoms into the spaces between larger atoms. The diffusion rate is faster than Vacancy Diffusion because there are fewer empty spaces (voids) compared to the number of atoms, so the probability of movement is smaller. If a room is almost completely filled with golf balls and ping-pong balls of similar size, it can be said that it is Vacancy Diffusion. If the room is filled with bowling balls and ping-pong balls of vastly different sizes, it is called Interstitial Diffusion. You can imagine the balls moving in each of these situations. Interstitial diffusion, which occurs between atoms with large size differences, is mainly found at the interface between gases and solids.
Diffusion is a time-dependent phenomenon, so we can categorize it into two cases: steady-state diffusion and nonsteady-state diffusion. The factor that distinguishes steady-state diffusion from nonsteady-state diffusion is the diffusion flux. The diffusion flux is the amount of diffusion of mass per unit area per unit time in the direction perpendicular to the interface of metal to metal or metal to gas. If atoms from A move toward B and atoms from B move toward A in the same amount of time, and the sum of the diffusion fluxes is equal to zero, this is called steady-state diffusion. In Steady-State Diffusion, the amount of atoms moving in each direction is equal, so diffusion is actually occurring, but it looks like no diffusion is occurring. Nonsteady-state diffusion, on the other hand, is the state we see most often, and is the state that describes most of the conditions we see. The diffusion of atoms in one direction is so dominant that the value of the diffusion flux is not zero even when the diffusion of atoms in the opposite direction is taken into account. For example, if A’s atoms are moving toward B at a rate of 3 per unit time and per unit area, and B’s atoms are moving toward A at a rate of 5 per unit time, the diffusion flux will be 2 in the A direction. And from the outside, it would appear that only B’s atoms are moving toward A by 2.
So far, we have seen how diffusion occurs in metals. Metals are indispensable in our lives, and their importance is growing every day. From steel plates used in large ships, airplanes, and cars to everyday smartphone cases and kitchen utensils, metals permeate almost every aspect of our lives. It’s fascinating to think that this seemingly solid and static metal is actually actively diffusing. Even now, metals are constantly diffusing to form new, stronger alloys. Understanding these dynamic properties of metals will not only deepen our understanding of our everyday lives, but will also play an important role in future technological advances.
