Grain size reduction

03/11/17

“Is it possible to increase the strength of a material by reducing the grain size?”
Many materials in their original form are not strong enough for practical engineering purposes. However, is there a way in which we could strengthen a material by modifying its grain structure? Well, let’s look into it. We know that the strength of a material is contingent upon its grain size. Specifically, the smaller the grain sizes are, the more of them will be able to be present within a material. So wouldn’t it logically follow that if we were to reduce the size of grains, the stronger our material would be? This is the fundamental principle behind grain size reduction, and modifies the yield strength of a material by the equation sigma =sigma_0+kdx, where sigma  is the new yield stress, sigma_0 is the original yield stress, k is a constant, and d is the grain size.

Precipitate hardening

03/10/17

“How can we use heat treatment to increase the strength of a material?”

Often times, when we receive a material, it is not durable enough for our needs. So how can we use a readily available process to increase the strength of a material? Well, let’s use both of our engineering and scientific mindset to find out. Well, we know that if were to introduce an alloy into the crystal structure, then the material would be strengthened. However, if we were to increase the temperature of a material and then rapidly cool it, the material would form a highly regular crystal and the precipitates would seep into the grain boundaries, therefore greatly strengthening the material. This process is known as precipitate hardening and is used to make a variety of materials stronger ranging from everyday aluminum to the internal wing structure of a Boeing 767

Solution hardening

03/09/17

“What happens to a crystal structure when alloys are introduced?”
As pure elements, most crystal structures are fairly linear and homogeneous in nature. However, what happens when another element with a different atomic radius is introduced, disturbing this uniformness? Well, let’s use our scientific mindset to find out. We know that when these due to intermolecular forces that like elements will be more attracted to like elements. From this standpoint, we also can observe that this interlocking will impede further dislocations and lock the movement and slip of the atoms. This form of material hardening has been termed solution hardening my Materials Scientists and Engineers, and is dependent on the size of the inserted atoms.

Screw dislocation

03/03/17

“What happens when a shear stress acts upon a crystal lattice?”
Crystal lattices are prone to imperfections, such as line defects. However, what happens when the crystal pattern experiences a shearing effect? Well, let’s use our scientific mindset to investigate this issue. Well, this will cause a rupture in the geometry which will result in a phenomenon known as a screw defect. Screw defects are so named due to the fact that if one were to walk from one edge of the dislocation to the other without jumping or falling, a screw like path would be formed.

Diffusion couples

02/26/17

“Why does diffusion happen between two solid materials?”
Diffusion is a most fascinating chemical and physical phenomenon, allowing a dense collection of an element to expand and suffuse itself into another. However, What is required for such an effect to occur between two solid items? Well, after many years of research, Materials Scientists and Engineers have discovered a little thing called diffusion couples. Diffusion couples are two items with point defects that are in close contact. When the temperature is elevated, then the atoms of these materials are more likely to moves around, and can “jump” into the holes of its neighboring material. As time approaches infinity, these two materials will become homogeneous with one another, therefore stopping the diffusion process.

Polycrystals

02/20/17

“How do we classify crystals that have their periodicity disrupted?”
One of the most fundamental properties of crystals is their periodic structure. However, because of the sheer complexity of the physical universe, a perfect specimen is very rare to obtain. Specifically, the smooth periodicity is often disrupted, and the molecules of crystals will be forced into different grains going in different directions. Because these objects are so common, materials scientists and engineers have decided to term these crystals polycrystals. This interlocking nature makes polycrystals stronger than their monocrystalline counterparts as well as more heat resistant.