Slide 2 Santa Rosa Junior College ENGR 45 Fall 2011 December 14,
2011 Slide 3 Purpose Cold Working Recovery Recrystallization Grain
Growth Procedure Results Conclusion Errors Slide 4 To document the
recovery, recrystallization, and grain growth phases of cold-worked
carbon steel. Slide 5 Increasing strength through plastic
deformation and increasing dislocations Cold working because
deformation temperature drastically less than melting Higher
dislocation density, more hindered dislocation movement, increase
hardness Elongates grains
http://www.the-warren.org/ALevelRevision/engineering/img2/coldrolling.gif
http://adsabs.harvard.edu/abs/1985MTA....16..703C Slide 6 Applied
heat increases dislocation motion Metal decreases in hardness as
dislocations leave faster Additionally, original electrical and
physical properties are restored
http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Graphics/Recovery.gif
Slide 7 Continuation of recovery Continued decreasing dislocation
density New grains form between larger grains Start small,
eventually engulf parent grain boundaries Recrystallization
temperature for carbon steel is about 1000F Possible to increase
rate of recrystallization by increasing %CW
http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Graphics/Recovery.gif
http://info.lu.farmingdale.edu/depts/met/met205/annealingstages.html
Slide 8 Recrystallization completes, continued applied heat Grain
growth due to migration of grain boundaries outward Large range of
grain sizes
http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Graphics/Recovery.gif
Slide 9 Cold work a 40 cm long carbon steel wire to approximately
55% CW Cut wire into 12 equally sized pieces and assort into two
groups of 6 Heat one group at 500F and the other at 800F Take one
metal out of each after 1, 5, 10, 30, 60 minutes, and 24 hours Make
two molds of each group taking note of how to distinguish between
the samples Sand, polish and etch the samples Use the microscope to
photograph each sample Slide 10 Slide 11 Slide 12 Annealing
Temperature: Annealing Temperature: 500F Time: Time: 1 minute
Magnification: Magnification: 300x Description: Description:
Recovery and minor recrystallization. Visible grain stretching.
Slide 13 Slide 14 Annealing Temperature: Annealing Temperature:
500F Time: Time: 5 minutes Magnification: Magnification: 300x
Description: Stretching not visible. New grains forming.
Description: Stretching not visible. New grains forming. Slide 15
Slide 16 Annealing Temperature: Annealing Temperature: 500F Time:
Time: 10 minutes Magnification: Magnification: 300x Description:
Description: New grains continuing to form. Increasing grain
boundaries. Dislocation density begins to decrease due to the
increased motion of the dislocations. Slide 17 Slide 18 Annealing
Temperature: Annealing Temperature: 500F Time: Time: 30 minutes
Magnification: Magnification: 300x Description: Grain size of
larger grains increasing. Smaller grain boundaries are forced
smaller. Dislocation density continues to decrease. Description:
Grain size of larger grains increasing. Smaller grain boundaries
are forced smaller. Dislocation density continues to decrease.
Slide 19 Slide 20 Annealing Temperature: Annealing Temperature:
500F Time: Time: 60 minutes Magnification: Magnification: 300x
Description: Description: Large grain boundaries continuing to
increase, forcing other grains smaller. Slide 21 Slide 22 Annealing
Temperature: Annealing Temperature: 500F Time: Time: 24 hours
Magnification: Magnification: 300x Description: Very large and very
small grain sizes visible. Grain growth is apparent. Number of
dislocations is much less than at the beginning of recovery.
Description: Very large and very small grain sizes visible. Grain
growth is apparent. Number of dislocations is much less than at the
beginning of recovery. Slide 23 Slide 24 Slide 25 Annealing
Temperature: Annealing Temperature: 800F Time: Time: 1 minute
Magnification: Magnification: 300x Description: More visible grain
stretching than in 500 F. Recovery phase. Description: More visible
grain stretching than in 500 F. Recovery phase. Slide 26 Slide 27
Annealing Temperature: Annealing Temperature: 800F Time: Time: 5
minutes Magnification: Magnification: 300x Description: New grains
forming, much larger than those formed in 500 F at same annealing
time. Description: New grains forming, much larger than those
formed in 500 F at same annealing time. Slide 28 Slide 29 Annealing
Temperature: Annealing Temperature: 800F Time: Time: 10 minutes
Magnification: Magnification: 300x Description: Large grains
increasing size, pushing adjacent grains smaller. Description:
Large grains increasing size, pushing adjacent grains smaller.
Slide 30 Slide 31 Annealing Temperature: Annealing Temperature:
800F Time: Time: 30 minutes Magnification: Magnification: 300x
Description: Description: Large grains continue to grow, forcing
others smaller. Dislocation density is decreasing. Slide 32 Slide
33 Annealing Temperature: Annealing Temperature: 800F Time: Time:
60 minutes Magnification: Magnification: 300x Description: Large
grains are very apparent. Notice the wide variety of grain sizes.
Description: Large grains are very apparent. Notice the wide
variety of grain sizes. Slide 34 Slide 35 Annealing Temperature:
Annealing Temperature: 800F Time: Time: 24 hours Magnification:
Magnification: 300x Description: Grain growth is very apparent in
larger grains. Smaller grains are much smaller than in previous
slides. Dislocation density is at its minimum. Description: Grain
growth is very apparent in larger grains. Smaller grains are much
smaller than in previous slides. Dislocation density is at its
minimum. Slide 36 Slide 37 Although some of the pictures of the
recrystallization of carbon steel did not match perfectly with the
theoretical outcomes we expected, we think that our experiment was
still successful because the overall stages still followed the
recrystallization model very closely. Slide 38 Pictures did not
come out as clearly as we had liked; over-etching and excessive
scratching made the patterns in the grains less noticeable or
difficult to see. Lack of a control sample makes it difficult to
compare the other metals without a base frame of reference.
Although the first metal was only heated for 1 minute, the fact
that the steel was so thin may have caused drastic changes in the
grain patterns. Slide 39 The extreme thinness of the carbon steel
may have caused the recrystallization process to end much faster,
resulting in the grain growth phase occurring much sooner. The
relatively small surface area of each metal may have caused the
patterns in the grains to be distorted. Near the edges of each
metal there was stretching of grains and other deformations. The
inside of the metal were so close to the edges of the metal that
the deformations may have extended to some of the grains in the
middle. Slide 40 http://www.the-
warren.org/ALevelRevision/engineering/i mg2/coldrolling.gif
http://adsabs.harvard.edu/abs/1985MTA....16..703C http://www.ndt-
ed.org/EducationResources/CommunityC
ollege/Materials/Graphics/Recovery.gif
http://info.lu.farmingdale.edu/depts/met
/met205/annealingstages.html Slide 41 Younes
