This document discusses the fabrication and testing of aluminum 7075-silicon carbide (SiC) metal matrix composites produced via stir casting. Al 7075 and SiC powders were mixed in varying weight ratios and cast into cylinders. Testing showed that hardness increased with higher SiC content and heat treatment. Wear resistance also improved with more SiC added. The composites demonstrated enhanced mechanical properties over the base aluminum alloy.

1. FABRICATION AND COMPRESSION OF
MECHANICAL PROPERTIES OF Al 7075, SiC BY
STIR CASTING

2.  Abstract
 Why this Project?
 Introduction
 Composition of Composites
 Matrix material properties
 Reinforcement material properties
 Methodology
 Testing
1. Hardness Test
2. Wear Test
 Conclusion

3.  Now a day’s Composites plays a key role in all manufacturing sectors
where the materials are required to have good mechanical
properties. Aluminium 7075 alloy with Silicon Carbide (SiC) as
reinforcement is used in high wear resistant and creep resistance
applications. Due to the concepts of high strength to low weight
ratio, Al 7075 was extensively applied in aircraft engine and wings.
For further enhancement of properties for increasing its applicability,
Al 7075 is reinforced with SiC. The Al 7075 and SiC were weighed by
using sensitive balance and were mixed on the basis of their weight
ratios.

4.  Composites are improving the design process and end
products across industries, from aerospace to renewable energy.
Composites offer design options that would be hard to achieve with
traditional materials.
 Each year, composites continue to replace traditional materials like
steel and aluminum. As composite costs come down and design
flexibility improves, it opens up new design opportunities for
engineers

5.  A material system composed of two or more phySiCally distinct
phases whose combination produces aggregate properties that are
different from those of its constituents.
 The constituents retain their identities in composite; i.e. they do not
dissolve or otherwise merge completely into each other, although
they act in concert.
 The main advantages of composite materials are their high strenght ,
stiffness , low cost, light in weight and high durable.
 Composite materials can be found in Aerospace industry, Cement
buildings, Automotive parts, Trees are technically composite
materials, high performance machines, etc.

6.  Generally, all composite material consist of two phases:
1. Matrix - Forms the matrix within which the secondary phase is
imbedded.
• “Aluminum 7075” is the matrix material we used.
2. Reinforcement - Imbedded phase sometimes referred to as a
reinforcing agent, because it usually serves to strengthen the
composite.
• “Silicon Carbide ” is the reinforcement material we used.

7.  Aluminium 7075 (Al 7075) :
1. 7075 Aluminium alloy can be further improved by how it is
strengthening using a process known as heat treatment.
2.Temperinng method can use high heat(300-500 C) to reconfigure
metal’s crystal structure to strengthen its overall mechanical
properties, and can literally make-or-break a material.
3.There are many methods of tempering 7075 Aluminium, but
simplify this article, we will highlight T6 tempered 7075 Aluminium
alloy .
4.7075-T6 is a common temper for Aluminium plate and bar stock.
5.However , it is important to know that each tempering process
gives 7075 Aluminium its own distinct values and characteristics

8.  Low density, High strength, Good high temperature strength
(reaction bonded) Oxidation resistance (reaction bonded) Excellent
thermal shock resistance, High hardness and wear resistance,
Excellent chemical resistance, Low thermal expansion and high
thermal conductivity.
 Fixed and moving turbine components Seals, bearings, pump vanes
Ball valve parts, Wear plates, Kiln furniture, Heat
exchangers, Semiconductor wafer processing equipment.

9.  Out of various furnaces, bottom pouring furnace is
suitable for fabrication of metal matrix composites
in stir casting route, this type of furnace consist of
automatic bottom pouring technique which
provides instant pouring of the melt mix (matrix
and reinforcement).
 Firstly the Al 7075 rods are placed inside the
furnance and melted at 500C with the help of
electrical heaters, the sensors inside the machine
gives information of temperature of the rods.
 Now the SiC is added into the furnance and the
stirring process has been started to form the
vortex.

10.  Now the mixture is taken into the mold, with 12mm dia and 150mm
length.
 The solidification takes place.
 Oxygen in air forms oxide on metal, so inert gas is used to protect the
material as they won’t involve in chemical reaction.

11.  Two different tests are conducted on the molded specimen, they are:
1. Hardness Test
• Before Heat Treatment
• After Heat Treatment
2. Wear Test

12.  Hardness is a measure of how much a material
resists changes in shape. Ability of material to resist
wear, tear, scratching, abrasion cutting is called
Hardness.
 This test undergoes on Micro Vickers Hardness Tester
 After hardness test, the specimen undergo Heat Vickers Hardness machine
treatment in muffle furnace.
 The specimen will constantly get heated at 400C for
2hrs, so that the specimen reaches to recrystallization
temperature.
 After reaching the recrystallization temperature, the
specimen is placed in water to make it cool.
Muffle furnace

13.  After the specimen get’s cooled, the hardness test is done again on
the specimen.
 We can observe that there will be increase in hardness.
 At recrystallization temperature the specimen is converted from
Coarse grain to Fine grain. Due to this the hardness of the specimen
Increases.
 Here VHN means Vickers Hardness Number.
 D1 and D2 are Diameters of Intender in Vickers hardness tester.
 2 trails are done on each specimen, trail 1 at front end of the
specimen and trail 2 for rear end of the specimen
 Formula for Vickers Hardness is,
HV= 1.854 (F/d) kgf/mm^2

14. Compositions Trail 1 Trail 2 VHN
D1 D2 VHN D1 D2 VHN
Al 7075+2% SiC 83 87 123 89 97 125 124
Al 7075+4% SiC 78 79 126 89 96 127 127.5
Al 7075+6% SiC 72 76 136 79 86 141 138.5
Al 7075+8% SiC 69 72 143 81 82 147 145

15. Compositions Trail 1 Trail 2 VHN
D1 D2 VHN D1 D2 VHN
Al 7075+2% SiC 79 83 138 67 89 141 140
Al 7075+4% SiC 77 78 149 78 93 145 147
Al 7075+6% SiC 69 56 156 78 91 159 157.5
Al 7075+8% SiC 82 68 167 82 79 162 164.5

16.  Wear resistance is defined as the ability of stone to resist
comprehensive external forces such as abrasion, edge cutting and
impact etc, during service.
 The amount of wear is calculated by the difference between initial
weight and final weight.
 As per ASTM standards the work piece should be 12mm dia and
25mm length.
 The sliding wear test was conducted
for applied load 9.81N for a sliding
distances of 200m, 400m and 600m.
After every test the wear was
documented to determine the wear
rate.
Wear test machine

17. S.no 1. Material 1. Initial
2. weight
1. Final
2. weight
1. Loss of
weight
1 Al 7075+ 2% SiC 11.949 11.9418 0.0072
2 Al 7075+ 4% SiC 11.968 11.9609 0.0071
3 Al 7075+ 6% SiC 11.468 11.4611 0.0069
4 Al 7075+ 8% SiC 11.548 11.5412 0.0068
Wear at 1kg load for 200m

19. S.no Material Initial
weight
Final
weight
Loss of
weight
1 Al 7075+ 2% SiC 11.9418 11.9350 0.0068
2 Al 7075+ 4% SiC 11.9609 11.9542 0.0067
3 Al 7075+ 6% SiC 11.4611 11.4546 0.0065
4 Al 7075+ 8% SiC 11.5412 11.5348 0.0064
Wear at 1kg load for 400m

21. S.no Material Initial
weight
Final
weight
Loss of
weight
1 Al 7075+2% SiC 11.9337 11.9204 0.0133
2 Al 7075+2% SiC 11.9530 11.9400 0.0130
3 Al 7075+2% SiC 11.4536 11.4409 0.0127
4 Al 7075+2% SiC 11.5339 11.5213 0.0126
Wear at 1kg load for 600m

23. The conclusions of the research work undertaken are;
 The Al 7075-SiC- metal matrix composite materials have been
fabricated by stir casting method followed by extrusion process.
 The nano SiC particulates are evenly dispersed in the matrix alloy.
The micro hardness of Al 7075-SiC metal matrix composite material is
superior than the matrix material. The micro hardness increases by
12.2% by the addition of 2 wt.% of SiC particulates in aluminum (Al
7075) matrix alloy.
 The inclusion of SiC particulates in Al 7075 matrix alloy significantly
enhanced the ultimate tensile strength and yield strength of the Al
7075-SiC 2 nano metal matrix composite materials.
 Shows 40.32% increase in the compression strength as compared to
compression strength of aluminum (Al 7075) alloy.

24.  The 8 wt.% of SiC reinforced aluminum (Al 7075)-SiC nano composite
shows 54.11% increase in the ultimate tensile strength as compared
to ultimate tensile strength of LM 13 alloy.
 The inclusion of SiC particulates in Al 7075 matrix alloy significantly
enhanced the ultimate tensile strength and yield strength of the Al
7075-SiC 2 nano metal matrix composite materials. The 8 wt.% of SiC
reinforced aluminum (Al 7075)-SiC nano composite shows 54.11%
increase in the ultimate tensile strength as compared to ultimate
tensile strength of LM 13alloy.
 The ductility of Al 7075-SiC- metal matrix composite material
decreases as compared to matrix alloy. The ductility decreases by
32.72% with the inducing of 2 wt.% of SiC-GR nano particulates in
aluminum (Al 7075) matrix alloy.
 The compression strength increases as the fraction of reinforcement
enhances in the matrix material. The 8 wt.% of SiC-GRreinforced as-
cast aluminum (Al 7075)- SiC nano composite.