Physical Metallurgy - Understand Crystal Structures

A: Picking the wrong lattice type here shows up as accelerated wall loss and an unplanned spool replacement mid-turnaround. FCC austenitic steels have a higher atomic packing factor, which reduces the number of high-energy surface sites and supports a stable chromium oxide film in oxygenated seawater, unlike BCC carbon steel where the oxide is non-protective.

A: Misreading this leads to brittle failure during hydrotest or startup, not a paperwork issue. BCC steels suffer a ductile-to-brittle transition because of restricted slip at low temperature; once above that transition, ductile tearing is not the hazard driven by crystal structure.

A: Using the wrong APF feeds bad density and diffusion estimates, which then cascades into heat-treatment errors. FCC has four atoms per unit cell and atoms touch along the face diagonal, giving an APF of 0.74 when the occupied atomic volume is divided by the cell volume.

A: Choosing the wrong structure shows up as cracked bends and rejected spools. FCC metals activate 12 slip systems at room temperature, allowing uniform plastic flow, whereas BCC needs higher thermal activation and HCP is slip-limited.