DEVELOPMENT OF A PERMANENTLY MODIFIED PISTON ALLOY 1.0 Method of Approach:
Experimental work was carried out to study the effect of
magnesium on the cast structure and the properties of Al-Si
alloys and it was established that above a certain level
magnesium remarkably modified the eutectic silicon . The
following results were observed :
1. The modification of silicon by magnesium was of a permanent
nature. 2- The resultant rnachanical properties were much better and
the casting characteristics of the alloy were improved.
based oil the results, an alloy based on At developed to assess its suitability for piston applications.
The composition of the experimental alloy is given in fable 1. Also given in the table are the composition of the conventional eutectic and hyper-eutectic piston alloy..


1.1 Casting Characteristics
Under casting characteristics, the following were studied: i) Fluidity, ii) Hot-tearing tendency, iii) Gas Levels,
iv) Shrinkage characteristics and v) Melt loss The results of the Casting characteristics are summarized in Table 1.2. .

1-2 Physical Properties 1.2.1 Density Weight is an important parameter for pistons, the lower it is,
"
the better- Therefore, the density values of the experimental
-..-■'■ ~ -••"." - -*• #
alloy and the conventional’ alloy were compared. The results are given in Table. 1.3.
The experimental alloy has lower density which is beneficial.

1.2.2 Coefficient Of Thermal Expansion ^' w
The coefficient' of thermal expansion for the experimental alloy was compared with the conventional eutectic and hyper eutectic alloys. The graphs of expansion versus temperature are plotted in Fig. 1.10. The results are tabulated in Table 1.4.
It is observed that the experimental alloy has thermal expansion in the same range as the eutectic alloy.


expansion with 2.5% Mg addition was comparable with the value ,for conventional eutectic alloy with only 10% Mg. It is probable that the increase in coefficient of thermal expansion due to higher magnesium content may be compensated by decrease in coefficient of thermal expansion due to higher silicon content.

I 1.3 Mechanical Properties
The following mechanical properties were evaluated for the experimental and conventional alloys, all after heat treatment.
a) Tensile Strength
b) Elongation
c) Fatigue Strength
d) Fracture Toughness
1.3.1 Tensile Strength and Elongation
The tensile strength values and elongation after full heat treatment (T6) for the experimental and conventional piston alloys are given in Table 1,5.
These results indicate that the experimental alloy has 25% more tensile strength than the conventional eutectic piston alloy (B).

1.3.2 Fatigue Strength
The result of the rotating bending load fatigue tests are given in Table 1.6.
It is observed that the experimental alloy had much

better fatigue properties than the conventional alloys. The test load was chosen at a fairly high level to ensure failure at a finite number of cycles. The experimental alloy showed more than 100% improvement over the conventional eutectic alloy. The conventional hyper—eutectic alloy showed very poor fatigue resistance.

The fracture toughness results for experimental and
conventional alloys are shown in Fig. 1.11. The Kq values
calculated from these results are given in Table 1.7. K
values could not be obtained as the validation test for thickness
1
of the sample failed.
Validation for K requires that,
lc
a) Pmax/P > 1.10
Q
b) Thickness of specimen, B >= 2.5 (Kq/sigrna ys)
The condition (b) is not satisfied.
The results indicate that the fracture toughness of the experimental alloy is comparable to the conventional eutectic alloy (T6 heat treatment) and slightly superior to the conventional hyper—eutectic alloy. These results compare well

with the values for cast aluminum-silicon alloys reported in literature and given in 2.7.2 in Table 2.5 (80).

1-4 Environmental Tests
Based on the encouraging results of the mechanical and
physical tests, a batch of pistons were produced with the
V*
experimental alloy and fully machined after heat treatment. The
casting properties, heat treatment response and mach inability were satisfactory.
On these pistons the following environmental tests were carried out and compared with the conventional alloys.
a) Wear resistance
b) Growth
c) Elevated temperature exposure strength
d) Elevated temperature strength
1.4.1 Wear Resistance
The result of the wear test in the reciprocating rig,at 0 a temperature of 150 C and at a pressure of 0.25 Mpa, for the

experimental alloy(A) and the conventional eutectic piston alloy(B) are given in Table 1.8. Fig. 1.12 is a plot of the wear rate versus duration of testing . The results indicate that the wear, in the experimental alloy is much lower than that in the conventional eutectic piston alloy (B).

1.4.2 Growth Studies
o The results of the growth studies carried out at 220 C
and exposure for 6 hrs followed by 18 hrs, are given in Table
1.9., for the experimental alloy and the conventional eutectic
alloy. The results indicate that the growth is in the same range
in both the cases.

Pistons made with the experimental alloy were heated for o 100 hrs at 200 C and after exposure for 10, 20, 30 and 100 hrs,

the hardness and tensile strength values were determined at room temperature and compared with the conventional eutectic alloys. The results are tabulated in Table 1.10.

The results indicate that the experimental alloy (A) has superior elevated temperature exposure properties compared with conventional piston alloys (B) and (C).
1.4.4 .Elevated Temperature Strength
' The results of the elevated temperature strength tests o conducted at 200 C are tabulated in Table l.ll. The experimental
alloy (A) had an average tensile strength of 229 Mpa compared
with 203 Mpa for the eutectic piston alloy (B) and 158 Mpa for
the hyper-eutectic, piston alloy (C). The corresponding average
elongation values were 1.3, 0.10, 0.34% respectively. The
stress-strain. curves are shown in Fig. 7.13. The results show
that the experimental alloy A had better elevated temperature
strength, than the conventional alloys B and C. It can also be

seen that the experimental alloy samples showed greater consistency in the tensile values compared to conventional alloys
B and C. i ,^ A

From the results of elevated temperature exposure strength and elevated temperature strength experiments it is clear that the. experimental alloy which has no nickel content still has satisfactory high temperature properties. These results agree well with the reported findings of Cathedral and Smart (71) and Timmons(72). The elimination of nickel from the alloy composition would have definite’ cost benefits.

1,4.5 Summary of results
The results of the various tests conducted on the experimental alloy A and conventional piston 8 and C have been consolidated and tabulated in Table 1-12 . From this it is clear that the experimental alloy (A) compares favorably with the conventional eutectic and hyper—eutectic piston alloys. In view of its superior properties in some of the aspects it may be functionally a better piston alloy.

CLAIMS
1. An optical information recording medium comprising a recording layer on a surface of a
support, wherein
the surface of the support has pregrooves comprised of plural grooves and lands positioned between adjacent grooves,
the pregrooves have a track pitch ranging from 50 to 500 nm,
a reflective layer, the recording layer, a barrier layer, and a cover layer are positioned in this order on the surface of the support, and a layer formed by curing an ultraviolet radiation-curable composition is positioned between the barrier layer and the cover layer, the layer having a glass transition temperature of equal to or lower than 25°C,
the recording layer ranges in thickness from 1 to 100 nm on the lands and from 5 to 150 nm on the grooves,
the recording layer comprises at least one azo dye compound selected from the group consisting of an azo compound and an azo metal complex compound comprising an azo compound and a metal ion or metal oxide ion, and
the azo dye compound has an attenuation coefficient ranging from 0.15 to 03 a; a wavelength of 405 nm.
2. The optical information recording medium according to claim 1, wherein the azo dye compound has a refractive index ranging from. 1.45 to 1.75 at a wavelength of 405 nm.
3. The optical information recording medium according to claim 1 or 2, wherein the azo dye compound has a thermal decomposition property such that a mass reduction rate is equal to or greater than 10 percent in a main reduction process in thermal mass spectrometry.
4. The optical information recording medium according to claim 3, wherein the azo dye compound exhibits a total quantity of heat generated in the main reduction process ranging from -200 to 500 J/g.
5. The optical information recording medium according to any of claims 1 to 4, wherein the azo dye compound has a thermal decomposition temperature ranging from 250 to 350*C.
6. The optical information recording medium according to any of claims 1 to 5, wherein the metal ion comprised in the azo metal complex compound is a copper ion,
7. The optical information recording medium according to any of claims 1 to 6, wherein a ratio of the thickness on the lands and the thickness on the grooves, the thickness on the lands/the thickness on the grooves, of the recording layer ranges from 0.1 to 1.
8. The optical information recording medium according to any of claims 1 to 7, wherein the
ultraviolet radiation-curable composition comprises 20 to 99 weight parts of monofunctional
(meth)acrylate and 1 to 80 weight parts of polyfunctional (meth)acrylate per 100 weight parts of the
ultraviolet radiation-curable composition.

9. The optical information recording medium according to any of claims 1 to 8, wherein
information is recorded by irradiation of a laser beam having a wavelength ranging from 390 to 440
nm.
10. A method of recording information onto the recording layer comprised in the optical
information recording medium according to any of claims 1 to 9 by irradiation of a laser beam
having a wavelength ranging from 390 to 440 nm onto the optical information recording medium.