1. Ti undergoes a polymorphic transformation from HCP to BCC structure when heated above 882C. Estimate
the % volume change that may occur in a sample of Ti when heated from room temperature to 900C. For
the BCC lattice, the lattice parameter is measured
This weeks problems are mostly on Fracture, Fatigue and Creep. Your Materials books (Callister used in
ES2001 or Askeland used in Grad Materials classes) should be helpful.
1. The following data were obtained for the steady state creep (Stage II) in Ni ba
AE 4718: HOMEWORK 1
March 24, 2015
The Ti is going to transform from HCP to BCC when heated as specied.
For the BCC crystal structure, the equation relating atomic radius and crystal structure is given by:
or R =
AE 4718: HOMEWORK 3
April 8, 2015
The main dierence between the two types of hot corrosion is temperature. Type I hot corrosion occurs at temperatures above about 950o C and was rst observed in aircraft gas turbines. It relies on
1. An article on Hot Corrosion is in the assignment 3 folder. Based on this article, summarize the
key features to type I and type II hot corrosion.
2. Rate the following alloys in terms of strength, corrosion resistance, and K IC (i.e. which is likely to
AE 4718: HOMEWORK 3
April 22, 2015
A few factors control KIC and fatigue crack growth rate in Al alloys. The volume fraction of constituent
particles decreasing results in improved fracture toughness, and coarser dispersoids in th
1. Based on Chapters 2 and 4, answer the following questions. a) What factors control K IC and
fatigue crack growth rate in Al alloys? b) What new heat treatable Ti alloy is becoming popular in
aerospace applications? C) In the chapter, there is a process
AE 4718: HOMEWORK 5
May 1, 2015
rT i = 0.145nm
MT i = 47.87
= 7.949 1026
rAl = 0.143nm
MAl = 26.98
= 4.480 1026
a 3 = 4rAl
c = 1.02a
a = 0.404nm
Vcell = a2 c = 1.02a3 = 1.02(0.404nm)3 = 0.0673nm3
1. The crystal structure of -TiAl was discussed in class. The FCT unit cell is also shown below.
Based on the unit cell estimate the theoretical density of -TiAl.
2. A reference on -TiAl is posted in the Assignment 5 folder. Based on this file, a) What ar