RU1836476C - Aluminium based casting alloy - Google Patents

Abstract

Cast aluminum alloy. FIELD OF THE INVENTION The invention relates to non-ferrous metallurgy, and in particular to light materials for use in aerospace engineering and other industries. Alloys based on the AI-Si-Mg-Cu system have the highest strength characteristics at room and elevated (up to 250 ° C) temperatures in combination with good processability. The aim of the invention is to increase the strength at room and elevated temperatures, above the level of the known alloy, taken for the prototype. To achieve this goal, an aluminum-based casting alloy containing silicon, copper, titanium is additionally alloyed with a metal from the group: zirconium, nickel, vanadium, chromium, antimony (silicon and copper content is changed) with the following ratio of components in weight%: Silicon 8.5 -15.0 Copper0.5-5.5 Magnesium0.2-1.0 Titanium0.1-0.7 material. The alloy contains, wt.%: Silicon 8.5-15.0; copper 0.5-5.5; magnesium 0.1-1.0; titanium 0.1-0.7; at least one metal selected from the group consisting of zirconium 0.01-0.5; nickel 0.01-1.0; vanadium 0.01-0.05; chrome 0.01-0.5; antimony 0.01-0.4; aluminum is the rest. The properties of the alloy are as follows: AB 380-450 MPa; 220 ° C 5z50 4-6%; OIQO 150 MPa. spoo 250? C 350? With 100 MPa, moo 2 tablets 35 MPa; HB - 120-130. a metal selected from the group containing: Zirconium 0.01-0.5 Nickel 0.01-1.0 Vanadium 0.01-0.5 Chromium 0.01-0.5 Antimony 0.01-0.4 Aluminum Other To obtain a high-strength and heat-resistant cast alloy The development was based on the following considerations: - to ensure high casting properties, the alloy must contain at least 8% silicon; -double alloy containing 8-15% silicon, it is necessary to alloy with copper and magnesium in the ratios in order to ensure a high degree of supersaturation of the solid solution in the quenched state, and during aging - a multi-stage process of phase transformations: CuAl2 and W (AlxMg5SUCu4) which could create a high microheterogeneity density inside the grains W 00 with ON Xь XI О СА)

Description

solid solution, which leads to high strength characteristics of the alloy;

- to inhibit the movement of dislocations, the grain boundaries must be blocked by particles of the second phases relatively densely adjacent to the peripheral zones of the solid solution grains. In addition, modifying additives Zr, TI, etc., should be provided to create a fine-grained structure of the alloy, which further contributes to an increase in their strength and ductility.

The study showed that the silicon content in the alloy should be 8.5-15.0%. This provides high casting properties and a lower tendency to form porosity of hot cracks. Silicon with aluminum does not form chemical compounds and is present as separate primary inclusions in hypereutectic alloys, and is also part of the L + SI double eutectic with a melting point of 577 ° C. The amount of which increases with increasing silicon content to 11.7%. If the alloy parts operate for a long time at high temperatures, the silicon content should be kept low. An alloy with a silicon content below 8.5% leads to a sharp decrease in the casting properties of the alloy, and an increase in the content above 15.0% leads to a decrease in the heat resistance of the alloy.

To increase the heat resistance (in the range of operating temperatures of 200-300 ° C), copper is introduced into the alloy in an amount of from 0.5 to 5.5%. Based on the ternary state diagram of the alloys of the Al-Si-Cu system, it was proved that there are no ternary compounds in this system, and the CuAl2 and Si phases form a ternary eutectic with a melting point of 525 ° C. Isotherms of the joint solubility of copper and silicon in aluminum show that a triple-solid solution may contain a sufficiently large amount of copper (up to 5.5%), which should contribute to the hardening of the alloy during heat treatment. With an increase in copper content, the structure of the Al – Si – Cu alloy system becomes more heterogeneous, which leads to increased (compared with other silumin) heat resistance. However, as the amount of copper increases (more than 5.5%), the alloy becomes more brittle. If the alloy parts are designed to operate at high temperatures, the copper content should be at the upper limit, if at room temperature, but at the lower (s).

To increase the mechanical properties of en-lava, magnesium is added to it in an amount

0.1-1.0%. Magnesium and silicon form the hardening phase MgaSI, which crystallizes in a finely divided form. The solubility of Mg2SI in solid aluminum is very small (not more than 0.1%) at room temperature and 1.5% at quenching temperature. However, the aging process proceeds slowly and stepwise (CHP-p-p), and MgsSI particles are released in finely divided form; as a result, the strength of the alloy is significantly increased. When the magnesium content is less than 0.1%, the tensile strength and yield strength are reduced, and with an increase of more than 1.0%, the ductility of the alloy decreases.

Alloying the alloy with titanium in an amount of 0.1-0.7% leads to an increase in tensile strength and elongation. Titanium forms the AbTI phase with aluminum, the particles of which are crystallization centers, grind grain and solid solution, thereby increasing the mechanical properties of the alloy. At a titanium content of more than 0.7%, the phase coarsens and appears in the form of large particles, causing the alloy to become brittle. With a titanium content of less than 0.1%, there is no modification effect.

Zirconium, as an element of the transition group, is prone to the formation in the crystallization process of a supersaturated β-solid solution in aluminum, stable at elevated temperatures, and also has a significant modifying effect on the alloy structure. Zirconium forms the double AbZr compound with aluminum, not forming complex compounds with silicon and copper, and thus does not deplete the solid solution. The ultrafine particles of the AbZr intermetallic compound are additional crystallization centers. Zirconium in an amount of 0.01-0.5% helps to increase the tensile strength and elongation at room and long-term strength at elevated temperatures. An increase in the zirconium content above 0.5% decreases the mechanical properties of the alloy due to the formation of an excess AlsZr phase.

Alloying the alloy with elements with a low diffusion coefficient (copper, nickel, vanadium, chromium) promotes the formation under conditions of a high crystallization rate of a supersaturated solid solution, stable at elevated temperatures. In addition, particles of the second phases (AUMgsSMCm, AleCuaNi, etc.), which interact little with the solid solution, block grains and strengthen from the boundary, therefore, the heat resistance of the proposed

alloy is higher than that of the prototype. But with a nickel, chromium, and vanadium content of less than 0.01%, the increase in heat resistance is insignificant, and with a nickel content of more than 1.0%, vanadium and chromium of more than 0.5%, a sharp decrease in mechanical properties occurs at room temperature.

The introduction of antimony into the alloy, which is an effective modifier of Al-Si eutectic, increases the strength characteristics of the alloy at room temperature. An antimony content of less than 0.005% does not produce a noticeable modifying effect, and an increase in the content of more than 0.3% does not increase the strength characteristics.

The chemical composition and properties of the investigated alloys are given in Table 1.2.

As can be seen from .2, the proposed method, in comparison with the prototype, has higher mechanical properties (tensile strength by 30%, elongation by 50% and heat resistance by 40%}.

Smelts weighing 30 kg were carried out in crucible furnaces of electrical resistance. The study of mechanical properties was carried out in a heat-treated state on standard samples of 0 10 mm, machined from chill blanks and samples of 0 12 mm, cast in sand forms.

An analysis of the data presented shows that the presented alloy has high mechanical properties at room temperature - and, at elevated temperatures (250-350 ° C), the properties of the alloy are 3 1% higher than the analogous values of the Al-Si system.

The pre-alloy-based alloy based on aluminum will find application as a high-strength and heat-resistant material.

For m / l of the invention

Aluminum-based casting alloy containing silicon, copper, magnesium, etc. characterized in that. with tsezh.k. increased mechanical properties at room and elevated temperatures. h, os-s additionally contains at least one metal selected from the group consisting of zirconium, nickel, vanadium, chromium and antimony in the following ratio of components, wt.%:

Silicon 8.5-15.0

Copper0.5-5.5

Magnesium 0.1-1.0

Titanium .0.1-0.7

at least one metal selected from the group comprising:

Zirconium0.01-0.5

Nickel 0.01-1.0

Vanadium 0.01-0.5

Chrome 0.01-0.5

Antimony 0.01-0.4

Aluminum Rest

Table 1

Continuation of the table, 1

Table 2