材料代写-2PM
时间:2022-04-27
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UNSW SYDNEY

SCHOOL OF MATERIALS SCIENCE AND ENGINEERING


Tuesday, May 4th, 2021
2PM – 4PM

MATS3001 MICROMECHANISMS OF MECHANICAL BEHAVIOUR OF METALS

EXAMINATION GRADING: 40% of total grade for MATS3001

(1) TIME ALLOWED – 2 HOURS
(2) ANSWER ALL QUESTIONS
(3) THE VALUE OF EACH QUESTION IS INDICATED
(4) INSTRUCTIONS FOR THIS EXAMINATION ARE ON THE FOLLOWING PAGES

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MATS3001 END OF TERM EXAMINATON (40 marks)

Answer all the questions on the following pages. The expected length of the answer to each
question is indicated.

You should type your answers, save as a MS Word or pdf file, and then submit your file via Moodle
before the end of the examination time. Use 12pt font.

Note that the submitted file will be checked for similarity with other students’ answers, internet
sources and the lecture notes/online tutorials, so you must write in your own words. Hand-written
answers will not be marked. If you make any assumptions in answering the questions, state your
assumptions.
You can include figures to help explain your written answers if you wish (it is not compulsory).
Your figures can be drawn by hand or using your preferred software. If you can’t/don’t have time
to embed your figures in the same file with your written answers to the questions, a separate file
with figures can be uploaded. Similarly, responses which show mathematical solutions can be
handwritten. A single file with your figures/ mathematical solutions should be uploaded using
Moodle. For example, if you draw figures on paper by hand, then take a photo of the drawn
figures and upload the photo to Moodle. You will have 30 minutes after the end of the exam time
to submit your figures (i.e. until 4.30 PM on Tuesday, May 4th). Your submitted Word/pdf file with
typed answers to the questions must refer to all figures (e.g. write “see Figure 1” in your typed
answer, and the relevant figure should be labelled as “Figure 1”).
If your internet connection fails at any time, you should take a photo/screenshot showing some
evidence of the problem, clearing showing the current date and time. Send an email to Professor
Paul Munroe informing him of the problem as soon as possible. You can email your file(s) for Part
1 to Paul Munroe (p.munroe@unsw.edu.au) if the problem is specifically related to accessing
Moodle.
There is a declaration in Moodle which you must read before you commence the exam. You can
read it in advance of the start of the exam.
In addition to the declaration, note that communication with others during a final examination is
unacceptable and will be considered a breach of the UNSW Student Code of Conduct:
https://www.gs.unsw.edu.au/policy/documents/studentcodepolicy.pdf
The examination is designed to test each student's understanding and knowledge of the course
content and whether each student has met the course’s learning outcomes. Collaboration and
collusion are unacceptable. Use of sources such as Chegg is unacceptable; Chegg will be searched
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after the exam to check if any students have used this site. Cutting and pasting answers from the
lecture notes or other sources, and submitting them as your own work, is unacceptable.
Your submitted answers must be your own work.
If, during or after the examination, we detect that any students have communicated during the
examination or otherwise engaged in collusion, action will be taken under the Student Misconduct
Procedure: https://www.gs.unsw.edu.au/policy/documents/studentmisconductprocedures.pdf
The usual penalty in these cases, if proven, is 00 FL for the course though harsher penalties can
apply.
In previous terms, students have acted as whistleblowers and have provided screenshots of
messages sent during examinations and these have been used as evidence in student misconduct
investigations. If you have evidence of collaboration or collusion during an exam, you can contact
Professor Paul Munroe, Dr Owen Standard or Professor Michael Ferry; you can remain anonymous
if you wish.
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Question 1 (8 marks – suggested response length ~ 15-20 lines, 12pt font)

To what extent are a) the particles themselves or b) the dislocations arranged around the particles
responsible for increasing strength in a dispersion hardened alloy? Explain your reasoning.


Question 2 (8 marks – suggested response length mathematical working plus 5 lines of text, 12pt
font)













Find above Hall-Petch data for an interstitial free (IF) steel and the same steel with additions of 1,
2, and 3 wt.% Ni.
a) Determine the value of k for the “3 Ni” alloy.
b) For the IF steel without any Ni, calculate the yield strength for a material with a grain size
of 10 microns
c) Explain why the yield strength of the “3 Ni” alloy is greater, for any given grain size, than
that for the IF steel.
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Question 3 (6 marks – suggested response length ~ 10 lines, 12pt font)
SS310 is a grade of austenitic stainless steel containing 0.25 wt.% carbon. Its typical room
temperature yield strength is ~210 MPa. In comparison, AISI1018 is a mild steel that typically
contains 0.15 wt.% C, but exhibits a yield strength of ~400 MPa at room temperature. Why is
AISI1018 stronger than SS310?


Question 4 (10 marks – suggested response length ~ 15-20 lines, 12pt font)


















The above figure shows ageing curves for a 2xxx Al alloy for a range of heat treatment
temperatures.

a) Why does it take much longer to reach the peak aged condition at 121°C compared to
260°C?
b) Would you recommend that this alloy be used in service at 110°C? Justify your
recommendation.
c) During ageing at 149°C, the alloy becomes less strong in the first hour of ageing. What
changes in the microstructure of the alloy might be occurring at this stage to lead to
this softening?


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Question 5 (8 marks – suggested response length ~ 5 lines plus mathematical working, 12pt font)


The above data shows a Larson-Miller plot for a cast nickel-based superalloy (Inconel 792) used for
jet engine components. (Assume C = 20). What is the maximum operational temperature such that
failure should not occur in 10 years at an applied stress level of 200 MPa?

Inconel 792 contains 12.7 wt.% chromium and 3.2 wt.% aluminium (as well as other alloying
additions). Explain the reasons why a) chromium and b) aluminium are common alloying additions
in nickel-based alloys.


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