Let's Get Physical
True or False: Higher percent cold work leads to smaller recrystallized grain size.
True.
As the amount of cold work increases, the number of nucleation sites for recrystallization increases, often leading to smaller recrystallized grains.
In this mill configuration, the direction of the workpiece is reversed after every pass using elevator mechanisms.
Three-high mill
What does FRACAS stand for?
Failure Reporting, Analysis, and Corrective Action System
True or False. The main advantage of forging process over other metalworking processes is the control of fiber flow lines in the microstructure.
True.
Annealing process that produces soft (coarse) pearlite.
Full annealing
The value of the diffusivity, D, of an atom varies in an alloy.
True or False: Dsolute < Dsolvent
False.
Give all three principal stresses in a thin-walled cylindrical vessel.
sigma hoop = Pr/t
sigma long = Pr/2t
sigma min = 0
This phenomenon is caused by defective metal flow in any metalworking process. In casting, this occurs when two solidification fronts meet.
Cold shut
Standard to follow in the preparation of metal specimen for metallography
ASTM E3
Designation for a Chrome-Moly-Ni steel with 0.4wt% carbon.
AISI 4340
Which of the following statements is/are TRUE?
I. Pure metals solidify at a rate controlled by heat conduction (diffusion)
II. Alloy solidification is controlled by solute diffusion.
a. Statement I is true
b. Only Statement II is true
c. Both statements are true
d. Neither of the statements are true
c. Both statements are true
This forging process is used to reduce the thickness using concave dies.
a. Cogging
b. Swaging
c. Edging
d. Fullering
c. Edging
Cogging - incremental bites
Swaging - reduce diameter/taper pipes and rods
Edging - concave dies
Fullering - convex dies
A questioning technique to determine the cause and effects of a specific problem or failure. The process repeats until something fundamental is determined.
Toyoda Analysis/Why-why analysis
There are two types of diffusion creeps:
In ___ creep, atoms move through the lattice (bulk) of the grain structure
In ___ creep, atoms diffuse along the grain boundaries.
1. Nabarro-Herring
2. Coble
Which element can increase hardenability of steel even when added in small amounts only?
a. Ti
b. Cr
c. B
d. Ca
c. B
Boron is highly effective in increasing hardenability at concentrations as low as 0.001-0.003%. It enhances hardenability by reducing the formation of ferrite at grain boundaries, allowing the transformation to martensite over a larger cross-section during quenching.
What is the carbon content (in %) of the peritectic liquid in the iron-carbon system?
a. 0.15
b. 0.51
c. 0.77
d. 0.10
b. 0.51
Which of the following is NOT a reason why you should not superheat your melt too much above the liquidus temperature:
a. higher delta T, higher fluidity
b. higher delta T, higher gas porosity
c. higher delta T, higher oxide formation
d. higher delta T, higher mold penetration
a. higher delta T, higher fluidity
What kind of failure mechanism that is achieved during rolling is shown in the figure?
Alligatoring
What microstructure is shown in the figure?
Tempered martensite
The specific measure of hardenability obtained from the Jominy End Quench Test is called:
a. Ideal Critical Diameter
b. Direct Quench Equivalent
c. Jominy Hardness Number
d. Jominy-Grossman Equivalent
a. Ideal Critical Diameter (DI)
During the initial stage of quenching, there is poor heat transfer. This is due to ____.
A vapor film being produced after the contact of the very hot work piece and the quenchant which impedes contact for heat transfer.
Which of the following defects is NOT solved by increasing the pouring temperature of the melt?
a. Misrun
b. Cold shut
c. Cold shot
d. Premature solidification
c. Cold shot
These are solid globules of metal entrapped in casting due to splattering during pouring. Solution to this is to reduce turbulent flow or have a better design.
What is the formula to obtain the plane strain fracture toughness KIc of a material?
KIc=Y*critical stress*sqrt(pi*cracklength)
In an AISI 1040 steel, how much is it composed by pro-eutectoid ferrite?
(0.77-0.40)/(0.77-0.025)=50%
An aluminum alloy used in aircraft is 2024-T3. What is the history of its heat treatment?
a. Solution heat treated and then coldworked
b. Solution heat treated and then artificially aged
c. Solution heat treated and then stabilized
d. Solution heat treated, cold worked and then artificially aged
a. Solution heat treated and then coldworked