CN101705397A

CN101705397A - Al-Si-Mg-Er rare earth casting aluminium alloy

Info

Publication number: CN101705397A
Application number: CN200910238471A
Authority: CN
Inventors: 聂祚仁; 郑学斌; 苏学宽
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2009-11-20
Filing date: 2009-11-20
Publication date: 2010-05-12

Abstract

The invention belongs to the technical field of metal alloy, and provides Al-Si-Mg-Er rare earth casting aluminium alloy which is characterized in that rare earth Er element accounting for 0.1-0.8% of the weight percent of final product is added into ZL101 alloy matrix. The ZL101 alloy comprises the following components by weight percent: 6.5-7.5 percent of Si, 0.25-0.45 percent of Mg and the balance of Al. As trace rare earth Er element is added, primary a-Al phase is thinned, eutectic silicon phase is changed into tiny coral shape from thick needle piece shape, the combination property of the alloy can be improved, the tensile strength and the yield strength are slightly enhanced compared with those of the alloy which has the original components and is not added with Er, and the elongation is 2 times higher than that thereof.

Description

A kind of Al-Si-Mg-Er rare earth casting aluminium alloy

Technical field

The invention belongs to field of metal alloy technology.

Background technology

Aluminium silicon is that cast aluminium alloy has good liquid fluidity, erosion resistance, and good weldability, low-shrinkage and low thermal coefficient of expansion are to use cast aluminium alloy the most widely.Hypoeutectic al-si alloy ZL101 (GB/T 1173-1995) is widely used in automotive industry and space flight production.The main effect that adds Si in the cast Al-Si alloy is the flowability that can improve alloy, reduces hot cracking tendency, reduces and loosens, and improves resistance to air loss, and the main effect that adds a small amount of Mg is to form strengthening phase Mg with Si ₂Si, the intensity of raising alloy.Going bad, Eutectic Silicon in Al-Si Cast Alloys is thick faller gill shape mutually in the Al-Si alloy of handling, silicon has isolated matrix mutually, reduced the intensity and the plasticity of alloy, and in the alloy owing to existing hard crisp silicon to be difficult to mechanical workout mutually, the alloy with this tissue can not be used for casting aluminum alloy parts.In addition, the Al-Si alloy has bigger air-breathing tendency in fusion process, is easy to generate needle pore defect, thereby the mechanical property of alloy is still not high enough.Changing the form of silicon phase, reduce its weakening effect to substrate performance, is the effective way that improves the aluminum silicon alloy performance.

Up to now, there is metamorphic element to comprise period of element Table I A, II A and lanthanide series rare-earth elements to the hypoeutectic Al-Si alloy eutectic structure.Industrial extensive employing strontium (Sr) is as alterant, but the affiliation that adds of strontium causes forming in the alloy pore, reduces alloy plasticity.The rare earth element Al-Si alloy eutectic structure that also can go bad, rare earth is rotten to have well long-lasting and remelting stability, and rare earth element has the stronger detergent power of degassing.In the present existing research, rare-earth elements La, Ce, Nd, Y and mishmetal have metamorphism to the eutectic structure of Al-Si alloy.Yet for the still unmanned research of the metamorphism of rare earth element er, particularly rotten mechanical property research does not afterwards appear in the newspapers as yet.

Summary of the invention

The object of the present invention is to provide a kind of novel Al-Si-Mg-Er rare earth casting aluminium alloy, its good combination property, particularly unit elongation improve about 2 times than the former composition alloy that does not add Er.

Al-Si-Mg-Er rare earth casting aluminium alloy provided by the present invention is characterized in that: added in the matrix of ZL101 alloy that to account for the final product weight percent be 0.1～0.8% rare earth Er element.The weight percent of Si is 6.5～7.5% in the described ZL101 alloy, and the weight percent of Mg is 0.25～0.45%, and Al is a surplus.

The preferred content scope of above-described rare earth Er is 0.25～0.45% of a final product gross weight.

The preparation method of this alloy adopts fine aluminium (99.99%), pure magnesium (99.92%), and is raw material through the Al-6%Er of vacuum melting master alloy, disposes the Al-Si-Mg-Er alloy of different Er content.Adopt crucible oven that alloy is heated to 720 ℃ of meltings, pure Mg is pressed in the aluminium liquid with bell jar; Alloy is used C at 720 ℃ ₂Cl ₆Degasification, refining are left standstill after 20 minutes temperature are risen to 750 ℃ of adding Al-6%Er master alloys, and teeming temperature is 720 ℃, and die temperature is 150～200 ℃ during cast.

The present invention is owing to added micro-rare earth Er element, nascent a-Al obtains refinement mutually, Eutectic Silicon in Al-Si Cast Alloys becomes tiny coralliform by thick faller gill shape, the over-all properties of alloy improves, tensile strength and yield strength slightly improve than the former composition alloy that does not add Er, and unit elongation improves about 2 times than the former composition alloy that does not add Er.

Description of drawings

The Brinell hardness of Fig. 1, as cast condition and T6 heat treatment state alloy and the change curve of Er content;

The alloy silicon phase pattern SEM microstructure of Fig. 2, Comparative Examples preparation;

The alloy silicon phase pattern SEM microstructure of Fig. 3, embodiment 2 preparations.

The invention will be further described below in conjunction with the drawings and specific embodiments.

Embodiment

Comparative Examples: adopt conventional gravitational casting to prepare the Al-Si-Mg alloy, used raw material is high-purity Al (purity is 99.99%), technical pure Mg (purity is 99.9%) and Al-12%Si master alloy.At first rafifinal 656.7g and Al-12%Si master alloy 838.4g are joined in the graphite clay crucible, molten alloy in resistance furnace, smelting temperature are 750 ℃.After treating that metal melts fully, with bell jar the pure Mg of 6.4g is pressed in the metal melt, alloy is used C at 720 ℃ ₂Cl ₆Degasification, refining.Be poured into after leaving standstill and make the Al-7%Si-0.4%Mg alloy cast ingot in the swage, teeming temperature is 720 ℃.

Embodiment 1: adopt conventional gravitational casting to prepare the Al-Si-Mg-Er alloy, used raw material is high-purity Al (purity is 99.99%), technical pure Mg (purity is 99.9%), Al-12%Si master alloy and Al-6%Er master alloy.At first rafifinal 631.7g and Al-12%Si master alloy 838.4g are joined in the graphite clay crucible, molten alloy in resistance furnace, smelting temperature are 750 ℃.After treating that metal melts fully, with bell jar the pure Mg of 6.4g is pressed in the metal melt, alloy is used C at 720 ℃ ₂Cl ₆Degasification, refining.Leave standstill after 20 minutes and temperature to be risen to 750 ℃ add the 25gAl-6%Er master alloys.Be poured into after leaving standstill and make the Al-7%Si-0.4%Mg-0.1%Er alloy cast ingot in the swage, teeming temperature is 720 ℃.

Embodiment 2: adopt conventional gravitational casting to prepare the Al-Si-Mg-Er alloy, used raw material is high-purity Al (purity is 99.99%), technical pure Mg (purity is 99.9%), Al-12%Si master alloy and Al-6%Er master alloy.At first rafifinal 581.7g and Al-12%Si master alloy 838.4g are joined in the graphite clay crucible, molten alloy in resistance furnace, smelting temperature are 750 ℃.After treating that metal melts fully, with bell jar the pure Mg of 6.4g is pressed in the metal melt, alloy is used C at 720 ℃ ₂Cl ₆Degasification, refining.Leave standstill after 20 minutes and temperature to be risen to 750 ℃ add 75g Al-6%Er master alloys.Be poured into after leaving standstill and make the Al-7%Si-0.4%Mg-0.3%Er alloy cast ingot in the swage, teeming temperature is 720 ℃.

Embodiment 3: adopt conventional gravitational casting to prepare the Al-Si-Mg-Er alloy, used raw material is high-purity Al (purity is 99.99%), technical pure Mg (purity is 99.9%), Al-12%Si master alloy and Al-6%Er master alloy.At first rafifinal 531.7g and Al-12%Si master alloy 838.4g are joined in the graphite clay crucible, molten alloy in resistance furnace, smelting temperature are 750 ℃.After treating that metal melts fully, with bell jar the pure Mg of 6.4g is pressed in the metal melt, alloy is used C at 720 ℃ ₂Cl ₆Degasification, refining.Leave standstill after 20 minutes and temperature to be risen to 750 ℃ add the 125gAl-6%Er master alloys.Be poured into after leaving standstill and make the Al-7%Si-0.4%Mg-0.5%Er alloy cast ingot in the swage, teeming temperature is 720 ℃.

Embodiment 4: adopt conventional gravitational casting to prepare the Al-Si-Mg-Er alloy, used raw material is high-purity Al (purity is 99.99%), technical pure Mg (purity is 99.9%), Al-12%Si master alloy and Al-6%Er master alloy.At first rafifinal 456.7g and Al-12%Si master alloy 838.4g are joined in the graphite clay crucible, molten alloy in resistance furnace, smelting temperature are 750 ℃.After treating that metal melts fully, with bell jar the pure Mg of 6.4g is pressed in the metal melt, alloy is used C at 720 ℃ ₂Cl ₆Degasification, refining.Leave standstill after 20 minutes and temperature to be risen to 750 ℃ add the 200gAl-6%Er master alloys.Be poured into after leaving standstill and make the Al-7%Si-0.4%Mg-0.8%Er alloy cast ingot in the swage, teeming temperature is 720 ℃.

The ingot casting that obtains in above-mentioned 4 embodiment and 1 Comparative Examples is processed into tension specimen by GB228-2002 metallic substance tensile test at room temperature method, then after T6 thermal treatment (540 ℃/8h hardening+155 ℃/6h timeliness), the tensile mechanical properties of the different Er content alloy of test is as shown in table 1 on the MTS810 material stretch test machine.

As can be seen from Table 1, when the Er addition was 0.3wt.%, tensile strength of alloys and yield strength were respectively 305MPa and 261MPa, did not slightly improve when adding the Er element, and unit elongation is 6.2%, had improved about 2 times when not adding Er.Tensile strength is the maximum stress value that material bears before breaking, and yield strength is the actual operating limit of material, and the big more illustrative material plasticity_resistant deformation ability of its value is strong more.Unit elongation is big more, and the plasticity of illustrative material is good more.

Fig. 2 is the Brinell hardness of as cast condition and T6 heat treatment state alloy and the change curve of Er content.The hardness value of material is the concentrated expression of the strength of materials and plasticity.Because the adding of Er element makes crystal grain obtain refinement, the hardness of cast form value increases in the alloy.This alloy is heat-treatable strengthened alloy, and strengthening phase is Mg ₂The Si phase, the Mg of diffusion-precipitation in the solid solution aging process ₂The Si phase produces dispersion-strengthened effect.In addition, a part of Er element of solid solution is separated out the Al of small and dispersed in the solid solution aging treating processes ₃The Er phase further increases the Brinell hardness number of alloy.

Table 1Al-Mg-Si alloy adds the tensile property under the T6 heat-treat condition of Er front and back

The cylindrical sample of the high about 10mm of ingot casting intercepting that Comparative Examples and embodiment 2 are made is that 10% HF solution carries out deep corrosion to alloy sample through polishing, polishing back employing volume fraction, uses scanning electron microscopic observation eutectic Si phase, shown in accompanying drawing 2 and accompanying drawing 3.Wherein accompanying drawing 2 and accompanying drawing 3 are respectively the microstructure after Al-7%Si-0.4%Mg alloy and the deep corrosion of Al-7%Si-0.4%Mg-0.3%Er alloy.As can be seen, Eutectic Silicon in Al-Si Cast Alloys becomes tiny coralliform by thick faller gill shape behind the interpolation Er element from accompanying drawing, and when alloy was subjected to action of pulling stress, place, the tip of faller gill shape silicon phase produced the stress concentration phenomenon, and crackle is germinating herein easily.The interpolation of Er element has improved the disadvantageous effect of silicon phase morphology to alloy, has improved the intensity and the unit elongation of alloy.

Claims

1. Al-Si-Mg-Er rare earth casting aluminium alloy, it is characterized in that: added in the ZL101 alloy that to account for this Al-Si-Mg-Er rare earth casting aluminium alloy weight percent be 0.1～0.8% Er, the weight percent of Si is 6.5～7.5% in the described ZL101 alloy, the weight percent of Mg is 0.25～0.45%, and Al is a surplus.

2. Al-Si-Mg-Er rare earth casting aluminium alloy according to claim 1 is characterized in that: the weight percent of alloy middle-weight rare earths Er is 0.25～0.45%.