06 Metals and Alloys Free Online FlashCards

How do mobile electrons affect metals?

Mobile, delocalized electrons help metals conduct electricity and heat.

Why can many metals deform without breaking immediately?

Metallic bonding is not strongly directional, so atomic planes can often slide past one another without immediate fracture. This contributes to ductility and malleability.

Why are FCC metals generally ductile?

Face-centered cubic (FCC) metals, such as aluminum, copper, and nickel, are generally ductile because their crystal structure provides many directions for slip.

What can limit the room-temperature formability of HCP metals?

HCP metals often have fewer easily activated slip systems at room temperature, which can limit their formability.

How do strength and toughness differ?

Strength is resistance to deformation or failure; toughness is the ability to absorb energy before breaking.

How can alloying increase a metal’s strength?

Alloying atoms, precipitates, and grain boundaries can impede dislocation motion, increasing strength or hardness, often at the expense of ductility.

How do cast irons differ from steels in carbon content and common use?

Cast irons contain more carbon than steels and are commonly cast into complex shapes. Some grades are comparatively brittle.

Why are low-carbon steels common in buildings and vehicle bodies?

Low-carbon steels are widely used in buildings, vehicle bodies, and machinery because they are relatively economical, formable, and weldable.

What does a phase diagram show, and what does it not predict by itself?

A phase diagram shows which phases are stable at equilibrium for specified temperatures and compositions; it does not by itself predict how quickly transformations occur.

What information does a tie line provide in a two-phase region?

A horizontal tie line in a two-phase region identifies the compositions of the coexisting phases; the lever rule can estimate their relative amounts.

Why is quenched steel tempered?

Quenching can form hard martensite in steel. Reheating below the transformation range during tempering reduces brittleness and adjusts the strength–toughness balance.

How does precipitation hardening strengthen an alloy?

Solution treatment and quenching create a supersaturated solid solution; aging then forms fine precipitates that obstruct dislocation motion and strengthen the alloy.