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Data on the impact of low temperatures on the tensile properties and impact values of various aluminum alloys. The authors report test results from different sources, including the Aluminum Research Laboratories and companies like Crane and Standard Oil Development. The data shows that aluminum alloys generally exhibit increased tensile strength, yield strength, and elongation at low temperatures.
Typology: Lecture notes
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FOR AERONA~km
By K. O. Bogardus, G. W. Stickley, and F. M. Howell
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The available sources of data on the rnechsnicalproperties of aluminum alloys at low temperatures are listed and a summary of the material to be found in each source is given.
From a review of the data presented by the authors of the articles reviewed, the aluminum alloys used commercially in
and the conclusions e~ressed general conclusions regsrding this country are drawn.
Many investigators exhibit not only higher
have reported that aluminum alloys in general tensile and yield strengths at low temperatures but also no loss of ductility. No evidence of embrittlement at low temperatures has been found in the commercial aluminum alloys but, in spite of this fact,,questions concerning this subject arise from time to time.
For this reason an attempt has been made to summarize briefly herein the available information on the mechanical properties of aluminum alloys at temperatures ranging from normal room temperature down to,the temperature.& boiling liquid hydrogen, -423° F. Although no claim is made to absol&e completeness, an attempt has been made to include all data available, starting with a pioneer report on this
arranged in the order in which they were published or becme available, in case they were never published. One of the most extensive investi- gations is the series of tensile tests carried out at the Aluminum Research Laboratories on a large nuniberof commercial aluminum alloys at temperatures ranging do}m to -320° F.
The kinils of tests used by the various investigators tensile, hardness, impact, and fatigue.
included
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I
Temperature Temper (°F)
Heat-treated
Heat-treated snd COhi- worked
Tensile Elongation strength (pe&t) (psi)
‘Gage length not given; probably 11.3 @FGZ
Rate of Loading on Mechanical Properties of Metals. Trsns. Am.
This paper describes tests on an aluminum alloy containing 3 per- cent copper, 0.42 percent iron, and 0.21 percent silicon in the form of wire 0.025 inch in dismeter. (^) The results were as follows:
Temper
Annealed at 300° C (572° F) for 30 tin
61-Percent reduction
92-percent reduction
Temperature (°F)
-g
-;;
Tensile stren&h (psi)
21, 24, 36,
Elongation in 2 in. (percent)
Reduction of srea (percent)
Sub-Committee, British ACA, 1921, pp. 92-106.
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The following paragraph is quoted from the summary report of tests made at the National Physical Laboratory”in England using sand-cast and chill-cast aluminum alloys of the t~es commonly used during World War 1, for aircraft-engine castings:
“The results of the tests indicate clearly that there is no merked decrease in the strength of sny of these alloys when they are exposed to low temperatures, either while the alloys are at the low temperatures or when they are subse- quently allowed to regain ordinary temperatures. On the contrary, it is found that at these low temperatures the alloys are markedly stronger, but that the strength becomes normal when they axe again raised to ordinary atmospheric temperature.“
The following results are listed:
P (^) Composition
2.5 percent Cu, 12.5 percent Zn
1 percent Mn
1 percent Mn
12 percent Cu
1 percent Zn, 1 percent Sn
Temperature (°F)
Room
Room
Room
Room
Room
-.
Chill-casting
Tensile strength (psi)
Elongation in 2 in. (percent)
Sad-casting
Tensile strength (psi)
Elongation in 2 in. (mercent)
.
,
0
k
-—_ ..—
... ... .—--—. ——... ———.._..—.-—
Temperature Br@ell Guillery Alloy (^) (%) hardness impact resistance
Commercial Al 70 24 11.
-301 to -310 (^) % ~i::
Durslumin 70 101 5. -4 96 5. -112 101 5. -166 107 ---- -301 to -310 129 5.
Al (15 percent Zn)l 70 55 11. -4 b7 11. -112 48.^ 10. -166 62 ---- -301 to -310 (^76) 9*
%0 alloy of this type is used in the U.S.
Properties of Metals snd Wood. Second cd., Naty Bur. Standards CircularNo. 101, U.S. Go,ti.Printing Office, 1924.
This report gives the ratio of Young’s modtius at 0° absolute to that at 0° C for aluminum as being 1.44. This was taken from an article “Elas- ticity of Metals as Affetted by Temperature” by A. Mallock in.the Pro- ceedings of the Royal Society of London, volume 95, series A, 1919, page 429.
The authors refer to tests reported in this summary in item (5), Rosenhain, Archbutt, snd Hanson, snd say:
“Tension tests on three typical alu&-num slloys at low temper- atures, -112° F, showed no decrease in tensile properties.”
Behaviour of Metals and The Jour. Inst. Metals,
J. A.: The Effect of Temperature on the Alloys in the Notched-Bar Impact Test. VOI.. xxxIv, no. 2, 1925, pp. 85-101.
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in impact values from 26.8 foot-pounds at room temperature to 36.2 foot- -poundsat -54° F. At -112° F results were variable, ranging up to 44.2 foot-pounds.
Duralumin was tested after quenching from 500° C both without and with aging. The aged materisl retained its strength at -4° F but declined about 4 percent in impact str&@h as the temperature dropped to -112° F. The unaged material increased about 6 percent at -4° F and -112° F.
Tensile tests using liquid air as the cooling medium gave the following results:
‘Tensile Yield Elongation Reduction Alloy Temperature strength strength in 2 in. of area (psi) (psi) (percent) (percent)
Cast, 1.0 percent Cu, Room 18,100 7,600 8.8 10. 0.8 percent W, Liquid air 17,800 8,100 7.0 (^) 7. 0.3 percent Si, 0.5 percent Fe
Cast, 0.2 percent Cu, Room 17,300 9,200 4.9 5. 5.0 percent Si, Liquid air 19,600 9,&)o (^) 3.7 4. 0.6 percent Fe
Liquid air 71,800 42,700 28.0 28.
These authors report on hardness and impact tests on notched bars of Lautal and 99.5 percent aluminum. The following table summarizes their results:
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On the basis of various reports, all of w~ch are covered separately in this book, the authors make these observations:
“When tested at low temperatures, aluminum alloys show increased tensile strength. Ductility, as measured by percentage,of elongation in the tensile test, seems to remain about the same as at ordinary temperatures, or even to increase slightly.”
The authors made measurements on wires with a torsion pendulum through the temperature range -20° to 500 c. They have determined the temperature coefficient of the modulus of rigidity for this temperature— range and list the following values:
.
L-
Alloy (^) Temper. Temperature coefficient
99.5 percent Al Anuealed -1oo to -135 x 10- Half-hard - Duralumin Heat-treated - unknown -
Lei&ngsdr*~ten bei ~iefen T&peraturen. Zeitschr. ffi Metallkunde, Bd. 22, Aug. 1930, pp. 261-263.
Tensile snd bending tests were made of pure aluminum and Aldrev (0.5 to 0.6 percent Sij‘0.3 percent Fe, of wire at various low temperatures.
The tensile tests were carried out -76° F. The bending tests were carried Results of these tests are shown in the
and 5.4 percent Mg) in the >orm
following table:
l
.. .----- -- .-—... ... ..- —— — .-- —--- —.^ -—-..——.-.—.——^ ----.—..——^ -—^.^ —-——
Alloy
?ure aluminum
Kldrey
0.6 percent Si, 0.3 percent Fe, O.k percent Mg)
.
Diam. of wire (in.)
Tem- per- ature (°F)
68 32
68 32
68 32 4 -;
Tensile strength (psi)
Elongation (percent)
Reduction of area (percent)
3ending “number (1)
%hehending radius was O.197 in. forthe 0.083- and O.110-in.-diameter wires snd 0.295 in. for the 0.142-in.-diameter wire.
,
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..—— ~— .— -.—.— (^) .——--
Alloy, temper, =a fO~
2S-0 rod
2s-H18 rod
3s-H18 rod
17S-0 rod
17S-T4 rod
25s-T6 rod
51S-0 rod
NO. 43, sana- cast
No. 195-T4, p ssnd-cast
Temper- ature
10ffset, 0.1 percent.. %eat-treated.
Tensile stre~h (psi)
Yield strength [:yi)
5@o 6,
8, 8,
23, 25,
Elongation in 2 in. (percent) ..
.
On the basis of these tests and test results published by others, the authors conclude that:
“Temperatures as low as that of liquid air (-320° F) do not have a harmful effect on sluminum alloys. On the c“ontrary, at such temperatures both the strength and ductility of aluminum alloys seem to be higher thsm at ordinary temperatures.”
Symposium on Effect of Temperature on the Properties of Metals,
issued jointlybyA.S.T.M. and A.S.M.E., June 23, 1931, pp. 486-508. .
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The author summarizes the results of investigations made by others between 190’5and 1931. Most of the pertinent data of his paper have been covered in this sumnaryby items (3), Sykes; (6), Guillet and Gournot; (10), Strauss; (15), Brombacher and Milton; and (17), Templin and Paul.
The author also lists the coefficient of thermal expansion of aluminum at -l~” F as 0.0000182 compared with 0.00002265 at 32° F (computed from International Critical Tables, vol. II, McGraw-Hill Book Co., Inc.j 1927, p. 459).
Metals at Low Temperatures. (^) Metallwirtschaft, vol. X, no. 31, 1’931,pp. 609-613; vol. X, no. 32, 1931, pp. 625-630. (As taken from Chemical Abstracts, vol. 26, Jan.-April 1932, p. 58.)
Tensile snd impact tests of seven forging alloys were made at temperatures as low as -310° F.
The authors state:
“The static tensile properties of all alloys examined rise considerably with lowering temperature, while the elongation and reduction do not chsnge as much.... Silumin and Lautal behave differently from the other aluminum alloys. The increase in tensile strength at low temperatures is accompanied by a drop in yield point and elastic limit. In the dynamic tests, the specific impact energy is highest at moderately low temperatures for most of the alloys, “whilethe elongation is practically constant.... Lowering ’thetemperature does not have as much effect on the dynamic properties as on’the static properties. All the alloys tested can be used at temperatures down to -190° C [-310° F~.”
The author made rounded-notch Charpy impact tests at -290° F.
He found that Scleron (1 percent Si, 4.5 percent Cu), rolled to 50,000-psi tensile strength, increased in impact resistance froml. to 1.75 meter-kilogrsms per squsre centimeter at -290° F. Laut~ (2 percent Si, 4.5 percent Cu), forgedto 53,000-psi tensile strength, ‘ and duralumin, heat-treated to 65 000-psi tensile strength, increased “in impact resistance down to -1106 F, then fell back at -290° F to about the room-temperat~e vslue.
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.. .- .. .... ...... .. .. .-.. —. —...._- ___ —.—________ ___ — .— ___ _. .. ——-—. ..--.—
..
,
1
Elastic Tem- (^) Modulus of limit Alloy Temper per-^ elasticity (^) (Offset, ature (°F)
(psi) 0.01 percent) (psi)
Duralumin 681B, Aged at 75 10,000,000 29, 3.6k percent CU, 0.47 Per- room -112 10,400,000 (^) 33,4Q cent Mg, 0.57 percent Mn, temper-. -310^ 10,800,000 44, 0.23 percent Si, 0.23 ~er- ature cent Fe
Duralumin 681zB, Aged at 75 10,200,000 kg, 4.21 percent Cu, 0.73 per- room -112 10,600,000 56, cent W, 0.63 percent M, temper- -310 lo,goo,ooo 64, 0.39 percent Si, 0.25 per- ature cent Fe
Lautal, Aged 60 75 9,800,000 “ 29, 4.21 percent Cu, 2.12 per- hr at -112 9,700,000 24, cent Si, 0.26 percent Fe 1400 c -310 10,500,000 31,
Silumin, Annealed^75 9,400,000 12,8Q 13.1 percent Si, 0.38 per- -112 9,400,000 13, cent Fe -310 8,700,000 10,
Scleron, Aged at^75 9,800,000 40, 3.o percentcu, 0.6Per- room -112 10,200,000 (^) 4a, cent Mu, 0.25 percent Si, temper- -310 10,700,000 (^) 56, 0.27 percent Fe, 12.0 per- ature cent Zn, 0.1 percent Li
Constructal 2, Aged for 75 9,900,000 (^) 39,M 1.2 percent Cu, 0.92 per- 25 k -112 10,400,000 42, cent Mg, 0.5 percent Mn, at -310 10,4OO,OOO 44, 0.56 percent Si, 0.26 per- 145° c cent Fe, 0.5 percent Ti
Constructeil87, Aged for (^75) 10,000,000 51, 1.62 percerit~, 1.24 per- 30 @ (^) -112 10,500,000 (^) 57, cent Mn, 0.29 percent Si, (^) at (^) -310 10,900,000 6h, 0.28 percent Fe, 6.87 per- (^) 75° c cent Zn
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—— —- —---..— .— ——- ---— ...— ...—-. __
The author presents”a formula for determining modulus at any temperature down to -310° F. The foregoing modulus values were not derived from the formula but sre taken from plottings of actual test resul.ts.
In the use of the formula the author makes this observation: ,, “Special reference maybe made to the lines for the alloys Silumin and Lautal,’for which a clear maximum vslue exists at a temperature of about -20° C ~4° F]. Both lower and higher temperatures cause a decrease of Young’s modulus. There is little doubt that the behaviour of these two alloys is caused by the content of silicon. The re-increase for Lautal at yet lover temperattn?esis probably a consequence of alloyed copper. Microscopic examination shows no altera- tion of structure.”
Concerning elastic limits at vsrious low temperatures the author says:
“These curves indicate a behaviour of the elastic limit, similar to that of modulus of elasticity.”
Daily Metal Reporter, vol. 30, no. 229, 1930, p. 8. (As reported from Metall&~ifal Abstracts, The Jour. Inst. Metals, l vol. L, no. 3, 1932, p..
“Comparative tests are described on alloys of the durslumin type (17S-T), on a propeller alloy (25S-T), @md on 2S and 3S, two simpler alloys, at 24° C and -800 C in order to determine their suitability for aero construction. The low-. temperature tests were carried out in a contairiercooledby a mixture of solid carbon dioxide and ether; they covered toughness, load-carrying capacity, snd tensile strength, and were applied by specislly designed machines. Both wrought and sand-cast alloys showed a definite increase in stlren@h.”
These British authors made tensile and Izod impact tests Of aluminum of commercial origin, in the form of l-inch round rolled bars at low temperature. The ssmples were annealed except in the case of “Y”. alloy which was quenched from 968° F in boiling water and aged 1 hour at 212° F. .
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..— — .-.. —.-—— -–- ————— —.-
off in the reduction of area at the lowest temperatures whereas Russell’s fi~es show a sli@t increase; howe~erj the elonga- tion figures of both alloys show some improvement at -180° C.”
Concerning their Izod impact tests, made at -40°, -184°, and -292° F~ the authors say that the increases in toughness at the lower temperatures were ammreciable for the pure aluminum but fcp “Y” alloy there was little sltera~ion between room t&perature and -292” F.
The following test results sre given:
Temper- ature (°F)
Room
Si, 0< Fe, 0,
Impact (f%-lb)
15percent, 17percent
Percentage increase over room temperature
--
“Y” Slloy (a)
Impact (ft-lb)
Percentage increase over room temperature
-- 7 7 7 14
composition, 3.46 percent Cu, 0.30 percent Si, 0.45 percent Fe, 0.08 percent kin,1.86 per-
bBroken clesn through.
kO Degrees of Metsls Used in Aircraft’Construction. Metal-sand ~OyS, VO1. 4, March 1933, Pp. 25-30. (See also: (^) Gillett, H. W.: Impact Resistance and Tensile Properties of Metals at Subatmospheric,Temperatures. ‘ A.S.T.M., Aug. 1941.)
Tensile, Brinell har~ess, Izod impact, and rotating-beam fatigue tests were made in a mechanically refrigerated room at Wright Field.
.
—— ——.— .—^ ——^ .—.
The authors report:
(^11)... the ductility as measuredly elongation and reduction of area is practically unaffected by the change from room temperature to (^) -40° C ~40° F]. There is an increase in tensile strength but in the case of the cast alloys this increase is too smsll to have any significance. Fatigue- l~ts are slightly higher at the low temperatures.”
“The fatigue properties of the notched specimens are raised [at -40° F] in about the ssme proportion as the unuotched specimens [in contrast to other metals].”
Th& following modulus-of-elasticity values sre shown:
Alloy
Temper
aSpecial heat treatment.
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