High-strength and high-toughness Al-Cu-(Al-Ti-Nb-B) alloy and preparation method thereof

Abstract

The invention discloses a high-strength and high-toughness Al-Cu-(Al-Ti-Nb-B) alloy and a preparation method thereof. The ratio of Ti to Nb of an Al-Ti-Nb-B intermediate alloy is determined to be 1: 1 according to thermodynamic calculation, the Al-Ti-Nb-B intermediate alloy is prepared by adopting a villiaumite reaction method, and the Al-Ti-Nb-B intermediate alloy is reprocessed by adopting a hot extrusion method. The Al-Cu-(Al-Ti-Nb-B) alloy disclosed by the invention is prepared from the following components in percentage by mass: 5% of Cu, 0.005-0.0125% of Ti, 0.005-0.0125% of Nb, 0.001-0.0025% of B and the balance of Al; and the phase of the alloy comprises one or more of NbAl3, TiAl3, TiB2 and NbB2 refining and strengthening phases, and the balance of Al2Cu and alpha-Al phase. The preparation method comprises the following steps: preparing an Al-Ti-Nb-B intermediate alloy, and carrying out hot extrusion and reprocessing; carrying out smelting and grain refining process of Al-Cu alloy melt; and preparing an as-cast alloy and carrying out T6 heat treatment. The grain size of the alpha-Al phase of the obtained alloy is smaller than 90 microns; and the maximum room temperature yield strength is 190.4 MPa, the tensile strength reaches 360.0 MPa, and the maximum ductility is 25.2%. The production cost is reduced, and the application range is expanded.

Description

technical field [0001] The invention relates to the field of non-ferrous metal materials and metallurgy, in particular to a high-strength and high-toughness Al-Cu-(Al-Ti-Nb-B) alloy and a preparation method thereof. Background technique [0002] Aluminum alloy has become the most popular non-ferrous metal due to its rich resources, low specific gravity, good mechanical properties, good corrosion resistance, and good electrical conductivity. and energy distribution and other fields have been widely used. In addition to the above traditional uses, aluminum alloys are also used as matrix materials for metal matrix composites such as stir casting, powder metallurgy, and mechanical milling. At present, aluminum is the second largest metal material after steel in a large amount and a wide range. [0003] Generally, cast aluminum alloys include Al-Si series, Al-Cu series, Al-Mg series and Al-Zn series, among which Al-Cu alloy has higher strength and high temperature performance t...

AI Technical Summary

Problems solved by technology

However, the strength of the Al-5Cu alloy is about 200MPa, which still does not meet the service conditions greater than 250MPa. The reason is that the dendrites of the α-Al matrix and the eutectic phase Al 2 Cu is too coarse, and Al 2 Cu belongs to the brittle phase, resulting in a decrease in strong plasticity

And in the casting process, the hot cracking tendency of Al-5Cu alloy is serious because its solid-liquidus line is relatively wide. In the later stage of solidification, a layer of liquid film is wrapped around the thick dendrite arms, which hinders the liquid phase between dendrites. Replenishment, lead to hot cracks, reduce casting yield

These defects limit the production and application of Al-5Cu alloy to some extent

[0006] However, the problems of this technology are: 1. Although the mechanical properties of the Al-5Cu alloy refined by Al-5Ti-B and Al-5Ti-0.75C have been improved, due to the intermetallic compound TiB 2 TiC and TiC do not belong to the strengthening phase, resulting in insufficient improvement in mechanical properties; 2. The grain size after Al-5Ti-B refinement is greater than 100 microns, and obvious dendrite arms can be observed, and the mitigation effect on hot cracking needs to be improved ; 3. TiC particles are unstable in the melt and easily react with liquid Al to form Al 4 C 3 , and then the phenomenon of thinning recession occurs

[0008] However, the problems of this technology are: the relative atomic mass of Nb atoms is large, and the formed intermetallic compounds are prone to sedimentation, which fails to achieve a refinement effect. The grain size is about 400 microns, and the coarse dendrite arms in the structure seriously affect the performance of the alloy, and the tendency of hot cracking is inevitable

[0010] After research, it is found that this technology still has the following problems: In the Al-Ti-Nb-B refiner developed for Al-Si alloys, because the addition of Nb has the effect of resisting Si poisoning, it is necessary to increase the Nb / Ti value, But for Al-Cu alloys, high Nb / Ti values ​​lead to MAl 3 and MB 2 The content of Nb atoms in the fine particles is too much, and there is still the problem of sedimentation

and excess MAl 3 and MB 2 The agglomeration effect of the refined particles will increase the particle size, reduce the efficiency of grain refinement, and the nucleation ability has not been fully exerted

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