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Keanu Mitchell Hoerip Tatetdagat

1206292023

Metallurgy and Material Engineering

Muhammad Husein Firdaus

1206229396

Metallurgy and Material Engineering

Material Testing Assignment 1

The differences output of mechanical properties in tensile test for HCP, BCC, and FCCare occurs because of their natural crystal structure. Crystal structures define the movement of

dislocation along the plane. Easier movement in the plane causing a material to deformed easier.

So in this case, if we use different crystal structure in the tensile test, the result will be different

for each kind of crystal structure. The deformation in tensile test is closely related with slip.

The mechanism by which plastic yielding takes place in metals is called slip. Essentially,all slip processes can be related to dislocation motion in the crystal structure. These linear

imperfections in the crystal structure determine the plastic deformation characteristics of a

Tensile Test material. Under elastic loading, dislocations remain motionless, and deformation

occurs at the interatomic level only. When loading is sufficient to "move" dislocations, slip is

said to have taken place and plastic deformation begins.

As slip begins, dislocations will start to move in certain favorably oriented crystal planes

in polycrystalline metals. The dislocations will eventually begin to pile-up at the grain

boundaries and, in order for slip to continue, dislocations must move in less favorably orientedslip planes in neighboring crystals. A greater stress is required for this to happen, and so the

material is said to become harder, or to strain-harden.

In HCP crystals, which include zinc and magnesium, the planes of closest packing are

those containing the hexagons, and the slip directions in those planes are parallel to the

diagonals. Hexagonal close-packed crystals therefore have three primary slip systems, althoughat higher temperatures other, secondary, slip systems may become operative.

Face-centered cubic crystals, by contrast, have twelve primary slip systems: the close-

packed planes are the four octahedral planes, and each contains three face diagonals as theclosest-packed lines. As a result, FCC metals, such as aluminum, copper, and gold, exhibit

considerably more ductility than do HCP metals.

In body-centered cubic crystals there are six planes of closest packing and two slip

directions in each, for a total of twelve primary slip systems. However, the difference in packing

density between the closest-packed planes and certain other planes is not great, so that additional

slip systems become available even at ordinary temperatures. Consequently, metals having a bccstructure, such as -iron (the form of iron found at ordinary temperatures), tungsten, and

molybdenum, has ductility similar to that of FCC metal.

Why HCP crystals are more brittle than FCC and BCC crystal? They tend to be more

brittle because they have fewer slip system than other structure. Because of this, fewer planes of

crystals can glide past each other under stress. Instead, the metal breaks.

Why FCC metals are more ductile than BCC metals? FCC has a higher packing

efficiency and the slip planes are more closely packed than BCC. In fact, BCC has more slip

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systems than FCC. But they are not as closely packed as FCC. For plastic deformation, we need

at least 5 independent slip systems. Both FCC and BCC have those. But the previously

mentioned factor makes FCC

more ductile than BCC.

Specimen standard for tensile

testing ASTM E8:

Specimen standard for tensile testing JIS 2201:

W (Widt) L (gauge length) P (Parallel

Length)

R (Radius of

Fillet)

T (Thickness)

25 50 60 approx 15 min Thickness ofmaterial

According to the table that I have research, the difference between the specimen ASTM E8 andJIS 2201 list of the size the result is all of the number in the table are different. There are no

similarities in each table. So I can conclude that ASTM and JIS has is not the same, since the

results are different.

Flat test specimen[7]

All values ininches

Plate type (1.5in. wide)

Sheet type (0.5in. wide)

Sub-size specimen(0.25 in. wide)

Gauge length 8.000.01 2.000.005 1.0000.003

Width 1.5 +0.125 -0.25 0.5000.010 0.2500.005

Thickness 0.25 < T