US3666451A - Aluminum alloy - Google Patents

Aluminum alloy Download PDF

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Publication number
US3666451A
US3666451A US63457A US3666451DA US3666451A US 3666451 A US3666451 A US 3666451A US 63457 A US63457 A US 63457A US 3666451D A US3666451D A US 3666451DA US 3666451 A US3666451 A US 3666451A
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United States
Prior art keywords
alloy
silver
zirconium
hardness
age
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US63457A
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English (en)
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Henry Dale Bewley
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US Atomic Energy Commission (AEC)
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US Atomic Energy Commission (AEC)
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
    • C22C21/08—Alloys based on aluminium with magnesium as the next major constituent with silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium

Definitions

  • the invention described herein was made in the course of, or under, a contract with the United States Atomic Energy Commission.
  • the present invention relates to an improved aluminum-base alloy. More particularly, it relates to a castable, corrosion-resistant, age-hardenable aluminum-base alloy having improved fatigue properties.
  • the axial-How compressor consists mainly of a rotor, stator, blades, and casing.
  • the rotor is a cylindrical drum with a shaft along its axis, with several rows of blades attached around the periphery of the rotor extending transversely to the rotor axis.
  • the stator is generally cone shaped and sits just outside the tips of the rotor blades defining an annular opening between rotor and stator from the suction end to the discharge end. Blades similar to the rotor blades are positioned in rows inside the stator. As the rotor turns, the gas to be cornpressed is drawn from the suction end, with each row of blades building up the gas pressure as the gas flows from suction to discharge end. Because of the combination of corrosion resistance, castability, and high strength-toweight ratio, aluminum alloys have been used as the material of choice for compressor components, especially compressor blades.
  • One of the best alloys used for this purpose is identified herein as the reference 214X having a composition consisting essentially of, in weight percent, 3 to 4.5 magnesium, 0.6 to 1.8 silicon, and the balance aluminum.
  • This alloy is readily castable into compressor blades, exhibits moderate tensile properties (less than 30,000 p.s.i. ultimate tensile strength) and fairly high fatigue properties (about 13,000 p.s.i. fatigue limit).
  • Compressor tests at high power levels show that the endurance limit or fatigue strength of the 214X alloy is exceeded resulting, in turn, in extensive deblading and damage to other compressor components.
  • This invention is based on the discovery that small additions of silver and silver with zirconium within specied limits lead to a hard, strong alloy capable, with appropriate 3,666,451 Patented May 30, 1972 erties of the 214X alloy. Silver in this range of concentration has been found effective to modify the aging process in a manner which involves interaction with diffusioncontrolling vacancies. Both vacancy and solute diffusion to sinks are restrained by the presence of silver in the concentrations used in this invention. Electron microscopy studies have shown that silver in effective amounts changes the 2l4X-type alloy by producing a tine, evenly dispersed precipitated phase as opposed to a segregated structure where any precipitated phase is bunched or associated mainly with grain boundaries.
  • FIGS. 1-3 are graphs in which FIG. l shows the effect of silver and zirconium alloying additions on the age hardening response at 350 F.
  • FIG. 2 shows the eiect of silver on age hardening induced at 350 C. relative to the reference 214X alloy.
  • FIG. 3 shows the improvement in fatigue properties obtained by silver and zirconium additions in an alloy aged to full hardness.
  • Improved structural stability of the new alloy of this invention is brought about by a combination of compositional as well as structural modification. This means that the addition of silver and/or zirconium alone to the reference alloy will not, of itself, lead to the improved result. It must, in addition, undergo an aging process, by which is meant that the composition-modified alloy must be heated to and held at a temperature which leads to the development of a secondary precipitated phase as characterized by electron microscopy. The development of this age-hardened condition is achieved by maintaining the silveror silver-and-zirconium-modied alloy at a temperature in the range 300-350" F. for a period of time suicient to produce a desired maximum hardness.
  • the development of a maximum age-hardening condition does not require a prior solution treatment but rather can be obtained from as-cast material.
  • the alloy is relatively insensitive to the cooling rate from the melt and both diecast and permanent mold-cast parts respond well to the aging treatment.
  • the age-hardening or precipitate-inducing temperature is 30D-350 F. Lower temperatures may be used, but the development of a maximum hardness level takes an inordinately long time. Higher temperatures than 350 E. up to as much as 500 F. can be used, but are not desirable because maximum hardness levels and associated strength properties are reduced.
  • Alloys within the scope of this invention can be melted and held in standard cast iron pots.
  • the silver can be added in the metallic form and dissolution of even relatively large ingots is rapid. Experience has shown that losses of silver from the melt are negligible even after a remelt operation.
  • the zirconium can be added either in the form of a zirconium containing ux or as a standard high zirconium aluminum base hardener. Additions by using the hardener are preferred. Zirconium melt losses may occur; so periodic compositional checks and new zirconium additions are needed to insure maintenance of the proper level of zirconium. Small permanent mold castings containing varying amounts of silver and zirconium to modify the reference 2l4X composition were produced from each resulting alloy to provide age-hardening, tensile, and fatigue test bars.
  • Age-hardening eiect Age-hardening tests were conducted on various cast specimens to test the effect of composition and prior fabrication history on the maximum achievable Rockwell Hardness.
  • the elect of alloying additions on the agehardening response of as-cast 214X reference alloy at 350 yF. is shown in FIG. 1, which is a Plot of hardness as a function of aging time at 350 F. It is seen from FIG. 1 that appreciable increments of hardness can be imparted to the reference 214X alloy by the addition of 0.9 percent silver and that further increments of hardness can be imparted by including small amounts of zirconium.
  • the silver modified alloys do not require a solution treatment to respond to aging
  • a comparison of the modified alloys with 214X after such a treatment (8 hours at 960 F. followed by a water quench) reveals that the addition of silver will effect the age hardening response.
  • Aging tests conducted on a 214K and 214X plus Ag alloy after a solution treatment have showed the solution-treated hardness of all the alloys to be somewhat below their as-cast values and that the 214X alloy without silver addition exhibited little response to an aging treatment.
  • the 214X plus 0.9 Ag alloy responded to reach a maximum hardness of '73 Rock-well Hardness in only l5 hours; the 2l4X plus 0.4 Ag alloy was intermediate in its response.
  • the agehardening behavior of solution-treated alloys is shown in FIG. 2.
  • the maximum hardness achieved at the age-hardening temperature will be maintained in the alloy so long as it is operated at temperatures below that used to introduce the age-hardening effect.
  • a plot of hardness-versus-temperature at any temperature below about 50 F. of the age-hardening temperature will show a constant hardness over an extended time.
  • Table Il demonstrate the remarkable irnprovement in endurance limit achieved by chemical and physical modification of the base of the reference 214X alloy, namely, by the addition of silver and zirconium combined with an aging treatment at temperature to produce a finely dispersed array of small age-hardening particles.
  • Table II shows, the endurance limit of silvermodiiied alloys subjected to an aging treatment at 350 F. was raised to 14,000 p.s.i. as compared to a silvermodiiied alloy without the aging treatment. The most dramatic improvement is shown with aged alloys containing zirconium. In that case the endurance limit was raised to 19,000 p.s.i., representing a 46 percent increase over the endurance limit of the as-cast 214X alloy. S/N curves (permissible stress/number of cycles before failure) are shown in FIG. 3.
  • the term consisting essentially of refers to essential elements of the alloy-to elements which are deliberately mixed to form the desired alloy having a desired combination of properties. It should, however, be understood that small amounts of other elements may be part of the alloy as claimed which are not deliberately added but which appear in the nal alloy in the process of its manufacture. Thus, such impurities as iron up to about 1.8 percent, copper up to 0.12v percent, and chromium up to 0.1 percent may be tolerated without adversely influencing the desirable qualities the alloy. Hence, the presence of such impurities in the alloy as a non-preferred condition is deemed to be within the scope of the claims.
  • a castable, age-hardenable, aluminum-base alloy consisting essentially of, in weight percent, 3.0 to 4.5 magnesium, 0.6 to 1.8 silicon, 0.4 to 1.5 silver, zirconium at a concentration in the range of 0.2 to 0.5, and the balance aluminum.
  • a compressor blade casting of an alloy consisting essentially of, in Weight percent, 3.0 to 4.5 magnesium, 0.6 to 1.8 silicon, 0.4 to 1.5 silver, zirconium at a concentration in the range of 0.2 to 0.5, and the balance aluminum, said alloy being in an age-hardened condition by heat treatment at a temperature above the intended service temperature.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Manufacture Of Alloys Or Alloy Compounds (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)
US63457A 1970-08-13 1970-08-13 Aluminum alloy Expired - Lifetime US3666451A (en)

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US6345770A 1970-08-13 1970-08-13

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US (1) US3666451A (enrdf_load_stackoverflow)
AU (1) AU455376B2 (enrdf_load_stackoverflow)
DE (1) DE2139965A1 (enrdf_load_stackoverflow)
FR (1) FR2105857A5 (enrdf_load_stackoverflow)
GB (1) GB1304509A (enrdf_load_stackoverflow)
NL (1) NL7111110A (enrdf_load_stackoverflow)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3868250A (en) * 1971-06-14 1975-02-25 Honsel Werke Ag Heat resistant alloys
US3876474A (en) * 1971-07-20 1975-04-08 British Aluminium Co Ltd Aluminium base alloys

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3868250A (en) * 1971-06-14 1975-02-25 Honsel Werke Ag Heat resistant alloys
US3876474A (en) * 1971-07-20 1975-04-08 British Aluminium Co Ltd Aluminium base alloys

Also Published As

Publication number Publication date
GB1304509A (enrdf_load_stackoverflow) 1973-01-24
NL7111110A (enrdf_load_stackoverflow) 1972-02-15
DE2139965A1 (de) 1972-02-17
FR2105857A5 (enrdf_load_stackoverflow) 1972-04-28
AU455376B2 (en) 1974-11-21
AU3161971A (en) 1973-01-25

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