carbon steel

Ductile Fracture in Medium Carbon Steel

Medium Carbon Steel and its Applications -

Carbon steel is steel in which the main interstitial alloying constituent is carbon in the range of 0.12–2.0%.

Mild Carbon Steel contains approximately 0.3–0.6% carbon content.

It balances ductility and strength and has good wear resistance; used for large parts, forging and automotive components.

Fracture and Microstructure of Medium Carbon Steel under Severe Plastic Deformation –

In medium carbon steel specimen, when subjected to severe plastic deformation, necking begins at the ultimate stress point. After necking, the medium carbon steel specimen fails resulting in cup and cone fracture surface as shown below.

Water quenching of Steel 45 (0.45%C; 0.27% Si; 0.65% Mn) at 800 °С for 1 hour was applied prior to deformation. After quenching, the steel microstructure is lath martensite (Fig.1b). The average size of martensite lathes was 8±0.5 µm, the average width of plates was 0.3±0.1 µm. A well-developed dislocation substructure is observed in the volume of martensite crystals in TEM images. The lattice parameter was a=2.868±0.00025 Å, which confirms the martensite solid solution saturation with carbon.

TEM: Travelling Electron Microscope                               SEM: Scanning Electron Microscope

Copper is a chemical element with symbol Cu (from Latin: cuprum) and atomic number 29. It is a soft, malleable and ductile metal with very highthermal and electrical conductivity. A freshly exposed surface of pure copper has a reddish-orange color. It is used as a conductor of heat and electricity, as a building material and as a constituent of various metalalloys, such as sterling silver used in jewelry, cupronickel used to make marine hardware and coins and constantan used in strain gauges and thermocouples for temperature measurement.

Copper is Malleable & Ductile

Copper can be formed and stretched into complex and intricate surfaces without breaking. This makes it possible to create spires, steeples, musical instruments, bowls, bed frames, tubes and a huge number of other useful and beautiful products. The very small diameter wires, which transmit power in cars, computers, televisions, lighting and mobile phones only exist because of the high ductility and malleability of copper.

Copper is a chemical element with symbol Cu (from Latin: cuprum) and atomic number 29. It is a soft, malleable and ductile metal with very highthermal and electrical conductivity. A freshly exposed surface of pure copper has a reddish-orange color. It is used as a conductor of heat and electricity, as a building material and as a constituent of various metalalloys, such as sterling silver used in jewelry, cupronickel used to make marine hardware and coins and constantan used in strain gauges and thermocouples The uniaxial tensile test using solid cylindrical tension specimens has been widely used to characterise the complete ductile fracture process in metals. The final ductile fracture in a tensile specimen is a result of a sequence of processes: (a) homogeneous deformation; (b) incipient necking; (c) nucleation of voids; (d) coalescence of voids; (e) crack formation; (f) shear deformation. Puttic] and Bluhm & Morrissey were among the first to identify the different stages of ductile fracture by performing controlled interrupted tensile experiments. Different stages of ductile fracture were also identified by LeRoy et a1[3] for various carbon steels. These investigations have led to a better understanding of the basic micromechanics of the ductile fracture process. Most of these studies, however, have been carried out on standard tensile specimens with uniform gauge length whereas it is well known that ductile fracture in metals is strongly dependent on the state of triaxial stress as shown by McClintock[4], Rice & Tracey[S] and Hancock & Mackenzie[6]. This paper presents results of controlled interrupted tests carried out on pure copper at quasi-static and intermediate rates over a range of triaxial stress states, in order to investigate the effect of stress state on the various stages of the ductile fracture. The experimental studies have not only led to a better understanding of the basic fracture process but have also been used to develop quantitative theoretical models to represent the different phases of the Process, though a comprehensive theory which can represent the complete process remains elusive. The Tvergaard-Needleman-Gurson for temperature measurement.

Grain growth and grain refinement behavior during deformation determine the strength and ductility of ultrafine-grained materials. We used asymmetric cryorolling to fabricate ultrafine-grained copper sheets with an average grain width of 230 nm and having a laminate structure. The sheets show a high-true failure strain of 1.5. Observation of the microstructure at the fracture surface reveals that ultrafine laminate-structured grains were simultaneously transformed into both equiaxed nanograins and coarse grains under tensile deformation at room temperature.

CUP AND CONE FRACTURE OF COPPER AFTER TENSILE TEST