Rajshahi University of Engineering & Technology
Department of Mechanical Engineering
Course No.: ME 3119
Course Title: Engineering Materials and Metallurgy
ASSIGNMENT
Submitted to:
Submitted by:
Roll: 2002001
Md. Mostafa Kamal
Assistant Professor
Class: 3rd Year Odd Semester
Mechanical Engineering
Session: 2020-2021
Rajshahi University of Engineering &
Date of Submission: 16-10-2024
Technology
1.a)
Mg Ca
1560
1320
830
X z
2 16
From the diagram
BE1CE2D=Liquidus Line
AE1F=First Eutectic Line;
GE2H:Second Eutectic Line;
E1=Eutectic points at 960℉ & E2= Eutectic points at 830℉
AE=Solvus Line; AB=Solidus Line
CG=Intermetallic compound Line; C=Intermetallic Compound CaMg2.
α=Solid phase of pure Mg ; β= Solid phase of pure Ca
Area AEXF: α + CaMg2 ; Area GXZH: β + CaMg2
AL1=Alloy Composition 1; AL2=Alloy Composition 2 and so on...
1600
Temperature(℉)→
1250
960
b) Time→
Fig 1.2:The cooling curve and the microstructure at various temperatures during the slow
cooling of a 70Mg-30Ca alloy
Just over the eutectic point(Relative amount)
45−30
L%=45−16×100% =51.7% (including 16Ca-84Mg)
30−16
S%=45−16×100% =48.3% (including 45Ca-55Mg)
At room temperature(Relative amount)
The solid portion would remain the same and only the liquid portion would turn into α and
CaMg2 zone below the eutectic point.
45−30
%Mg(s) in lamellar region= ×100% =33.33%
45
30
%CaMg2(s) in lamellar region=45×100%=66.67%
Microstructure:
c) Cooling curve at different composition alloy:
Fig 1.3:The cooling curve
d) At E1:
L→α + CaMg2
At E2:
L→β + CaMg2
2. Smart materials that have one or more properties that can be significantly changed in a controlled
fashion by external stimuli, such as stress, moisture, electric or magnetic fields,
light, temperature, PH, or chemical compounds.
Figure 2.1 Basic functioning of smart materials.
Smart materials include the ability to return to the original state after the stimulus has been
removed. Five common fundamental characteristics were defined as distinguishing a smart
material from the more traditional materials such as transiency, immediacy, self-actuation,
directness, and selectivity.
Types of Smart materials:
Figure 2.2 Smart Materials classification: examples of active and passive sms.
Descriptions and Applications
2.1 Piezoelectric materials
The piezoelectric materials have the ability to produce an electric potential as a response to an
input in the form of an applied mechanical stress and vice versa.Example: crystal (quartz),lead
magnesium niobate–lead titanate (PMN-PT), and barium titanate (BTO).
Applications:
1. In lighters or portable sparkers with a piezo fuze a sudden and strong pressure is used to
produce a voltage. The spark then ignites the gas.
2. Used in music for acoustic instruments.
2.2 Shape-memory alloys:
When heated, they belong to a class of metallic materials that have the ability to regain their
original shape after deformation. Nickel–titanium (niti), often known as Nitinol (shape-memory
strain of 8%), is the most well known SMA.It has strong corrosion resistance as well as good
fatigue behavior. The term "austenite state" (body-centered cubic) refers to the higher
temperature, while "martensite state" (complex rhombic structure) refers to the lesser degree of
temperature dependence. Physically, the material is strong and hard in the austenite state and soft
and ductile in the martensite phase.
Figure 2.3 Schematic illustration of shape-memory effect.
Applications:
1. Tiny actuators eject discs from computers machines and amazing bendable eyeglass
frames.
2. Used in aerospace morphing structure to reduce jet noise. Example: Engine nozzle
2.3 Magnetostrictive materials:
These materials show variations in magnetization in response to mechanical stress as well as
form changes in response to magnetic field. Magnetic energy may be transformed into kinetic
energy, or the other way around, using the magnetostrictive materials. The first magnetostrictive
material with strains of 50 ppm was Ni. The most well-known example, at 1500–1700 ppm, is
terfenol-D. They also feature a fine hysteresis loop, which reduces loss.
Figure 2.4 Strain trend of a magnetostrictive material due to changes in the magnetic field.
Applications:
Used in various applications such as magnetostrictive clamps,self-biased modular drivers,
omnidirectional loudspeakers, and helical line hydrophones.
2.4 Thermoresponsive materials
The majority of these materials are built using stimuli-responsive polymers. The stimuli includes
PH, temperature, ionic strength, light, humidity, electrical or magnetic fields, chemical, and
biological.
Figure 2.5 Curves showing phase transition phenomenon. (A) Lower critical solution
temperature (LCST) and (B) upper critical solution temperature (UCST) phase transition
behaviors of thermo-responsive polymers in solution [105]
It displays a temperature at which there is a significant shift in solubility. The lower critical
solution temperature (LCST) and the upper critical solution temperature (UCST) are two two
primary varieties of thermoresponsive polymers. The temperature at which a thermoresponsive
polymer, when heated, changes its characteristics from being hydrophilic to hydrophobic is
known as the LCST whereas the UCST exhibits the opposite behavior to the LCST when cooled.
Poly(N-alkyl-substituted acrylamides) are the most studied thermo-responsive polymers
exhibiting an LCST in water generally around 32°C.
Applications:
1. Poly(N-alkyl-substituted acrylamides) are valuable for pharmaceutical and biomedical
applications.
2. Including drug delivery system, rheological control additives, smart surface modification,
gene therapy, microfluidics, thermal affinity separation, temperature sensing and
nanotechnology, catalysis, bioengineering, oil industry, chromatography, mechanical
transducers (artificial muscles), reversible adhesion, etc.
2.5 Magneto-rheological fluids
When a magnetic field is applied to magneto-rheological fluids (mrfs), it alters the fluids'
viscosity and stress. An alternative term for mrfs is magneto-sensitive smart materials. Magneto-
rheological elastomers (mres) are soft particles that resemble rubber that may have their
mechanical characteristics altered by applying a magnetic field.
Applications:
1. The MR fluid damper is used in the washing machine to reduce vibrations during spin.
2. Magneto-Rheological Fluids have wide application Automotive Industry, Civil
Engineering, Household Appliances, Biomedical etc.
2.6 Chromic materials
Chromic materials are materials with a characteristic color change in response to external stimuli
(such as pressure, light, temperature, or electric field), especially when the change is reversible
and controlled. Since photodetectors have taken the position of eyes, color changes can occur in
visible, ultraviolet, or infrared spectrums.The chromic materials that change color in response to
light, heat, or electricity are known as photochromic, thermochromic, and electrochromic
materials, respectively.
Figure 2.6 Optical images of temperature-dependent visual color changes of
thermochromic materials
Applications:
1. Photochromic sunglasses. These glass lenses change color when they are held under
sunlight and regain their original color in shadow.
2. Huge application in thermometry, electronics, ophthalmics, and biomedicine.
3. Many varieties of dyes and pigments are used as chromic materials.
