CN100408716C

CN100408716C - Isothermal heat treatment method for modifying Chinese character-like Mg2Si phase for Mg-Al-Si series magnesium alloy

Info

Publication number: CN100408716C
Application number: CNB2006100952005A
Authority: CN
Inventors: 杨明波; 潘复生; 汤爱涛; 白亮
Original assignee: Chongqing Institute of Technology
Current assignee: Chongqing Institute of Technology
Priority date: 2006-10-14
Filing date: 2006-10-14
Publication date: 2008-08-06
Anticipated expiration: 2026-10-14
Also published as: CN1936062A

Abstract

The invention relates to an isothermal heat treatment method that is used to make metamorphism Mg-Al-Si series Chinese characters shaped Mg2Si phase in magnesium alloy. It includes the following steps: heating to 720-740 degree centigrade after smelting the constituents according to a certain ratio, removing the dross, taking gravity casting or sand casting, after the temperature decreasing below solution treatment temperature, putting the alloy into box shaped resistance furnace, and keeping thermal for 12-24 hours under the protective atmosphere, and taking out rapidly to temper into water. The invention expands the application range of Mg-Al-Si series magnesium alloy.

Description

Be used for rotten Mg-Al-Si series magnesium alloy Chinese character shape Mg 2The isothermal heat treatment method of Si phase

Technical field:

That the present invention relates to is Chinese character shape Mg in a kind of rotten Mg-Al-Si series magnesium alloy ₂The method of Si phase belongs to class of metal materials and field of metallurgy.

Background technology:

The Mg-Al-Si series magnesium alloy is considered to a kind of suitable high temperature and creep resistance magnesium alloy rising below 150 ℃ owing to have high-temperature behavior better and the advantage of aspect such as cost is lower.Wait magnesium alloy to compare with Mg-Al-RE system, the heat-resisting strengthening mechanism of Mg-Al-Si series magnesium alloy mainly is by introducing low-cost alloying element Si forms small and dispersed at the crystal boundary place Mg ₂Si realizes mutually.Because Mg ₂Si has high-melting-point (1085 ℃), the low density (1.99g/cm close with matrix mutually ^-3), high elastic coefficient and low thermal coefficient of expansion (7.5 * 10 ^-6K ^-1) etc. characteristics, it is at quite stable below 300 ℃, thereby makes the Mg-Al-Si series magnesium alloy have higher high-temperature creep resistance.In fact as far back as the seventies in last century, it is the research of heat resistance magnesium alloy that people have just begun Mg-Al-Si, and priority has been developed heat resistance magnesium alloys such as AS41, AS31, AS21 and AS21X, wherein the creep strength of AS41 alloy in the time of 175 ℃ is higher than AZ91 and AM60 alloy, and have good toughness, tensile strength and yield strength, and the creep strength of AS21 alloy and creep resistance temperature even also higher than AS41 alloy.Although these Mg-Al-Si series magnesium alloys of having developed have higher high-temperature behavior at present, its apply still because of its comprehensive mechanical property relatively poor etc. former thereby be subjected to a certain degree restriction.Narrate as the front, the heat-resisting strengthening mechanism of Mg-Al-Si series magnesium alloy mainly is to form Mg at the crystal boundary place by introducing low-cost alloying element Si ₂Si realizes mutually, but because the Mg that Si forms in the Mg-Al-Si series magnesium alloy ₂Si is many mutually to be occurred with thick Chinese character shape pattern, and the Mg of Chinese character shape pattern ₂There is very big stress concentration mutually on every side in Si, can promote the germinating and the expansion in micro-cavity in the alloy structure, and along with temperature raises, the cavity can increase thereupon, cause alloy mechanical property to reduce significantly, especially the easy more more slowly Mg that causes thick Chinese character piece form of unit elongation, and speed of cooling ₂Si generates mutually, makes the Mg-Al-Si series magnesium alloy be only applicable to rate of cooling die casting faster at present, and can't be used for technologies such as gravitational casting and sand mold casting.Therefore, how to strengthen Mg in the Mg-Al-Si series magnesium alloy ₂The rotten research of Si phase pattern makes Mg ₂Si by thick Chinese character shape topographical transition be small and dispersed distribute polygon-shaped and/or spherical, for the comprehensive mechanical property that improves and improve the Mg-Al-Si series magnesium alloy and and then enlarge its industrial applications and just seem particularly crucial.

During the nearly last ten years, both at home and abroad from alloying and/or microalloying angle, rotten Mg-Al-Si is Mg in the heat resistance magnesium alloy around alloying element ₂The Chinese character shape pattern of Si phase has been carried out number of research projects, and has successively reported that alloying elements such as interpolation The addition of C a, Sr, P or Sb can improve Chinese character shape Mg in the Mg-Al-Si series magnesium alloy ₂The result of study of Si phase.Based on these results of study, though add these alloying elements Mg in the Mg-Al-Si series magnesium alloy that can go bad to a certain extent in right amount ₂The Chinese character shape pattern of Si phase, but simultaneously again because these alloying elements interpolations bring separately problem to make by alloying and/or the microalloying Mg that goes bad ₂This method of Si phase pattern is subjected to certain restriction, as adding the component segregation that Sb brings and modification effect is not good, add the casting hot tearing that Ca brings and add Sr and problems such as adding mode that P brings and modification effect.Also, make by alloying and/or the rotten Mg of microalloying just because of the problem of these existence ₂This method of Si phase pattern also is difficult to satisfy the requirement of Mg-Al-Si series magnesium alloy industrial applications at present.

Summary of the invention:

The objective of the invention is to avoid the existing Chinese character shape Mg in alloying and/or the rotten Mg-Al-Si series magnesium alloy of microalloying that adopts ₂Si is this traditional method mutually, proposes to adopt Chinese character shape Mg in the rotten Mg-Al-Si series magnesium alloy of isothermal thermal treatment ₂The novel method of Si phase makes Mg ₂The Chinese character shape pattern of Si phase is rotten, so that the Mg-Al-Si series magnesium alloy can be used for technologies such as slower gravitational casting of rate of cooling and sand mold casting, enlarges the range of application of Mg-Al-Si series magnesium alloy.

To achieve these goals, the present invention proposes a kind of rotten Mg-Al-Si series magnesium alloy Chinese character shape Mg that is used for ₂The isothermal heat treatment method of Si phase.As seen from Figure 1; present method is that the Mg-Al-Si series magnesium alloy of certain ingredients is warmed up to 720～740 ℃ after by the composition proportion fusing; drag for alloy liquid surface scum; carry out gravitational casting or sand mold casting then; in castingprocesses after the temperature of alloy drops to solid solution temperature below the solidus temperature; alloy is put into chamber type electric resistance furnace, under protective atmosphere, be incubated 12～24 hours, take out in the entry of quenching fast then.

Adopt the rotten Chinese character shape Mg of present method ₂The mechanism of Si phase is: Mg ₂There are defectives such as dislocation and room at the interface in Si/Mg, lattice distortion is big, atom is in the higher-energy state, and these local atomic arrangement are generally irregular, openr, the atomic motion resistance is little, thereby for the Si atomic diffusion provides passage, so when solid solubility temperature carries out isothermal thermal treatment, thick Chinese character shape Mg ₂The Si atom of Si phase surface pit and high spot might break away from Mg gradually under the interfacial tension effect ₂The Si dot matrix is then along Mg ₂The Si/Mg interfacial diffusion enters the Mg dot matrix, and forms Mg in new position ₂The Si particle, and finally make Mg ₂Si phase pit is more and more darker, and until fracture, projection then flattens, thereby makes Mg ₂Si phase pattern becomes granular and/or spherical from the Chinese character shape, realize Chinese character shape Mg ₂Going bad of Si phase pattern.In addition, because alloy graining cooling and isothermal thermal treatment are among the successive processes, make alloy be in the higher state of temperature, the Si atom is at Mg always ₂Si/Mg diffusibility is at the interface strengthened greatly, makes the time that said process takes place shorten the easier Chinese character shape Mg that causes greatly ₂Going bad of Si phase pattern.

Therefore, adopt present method Chinese character shape Mg in the Mg-Al-Si series magnesium alloy that goes bad ₂Si handles mutually, when can carry out effectively going bad to the Mg-Al-Si series magnesium alloy, avoided traditional method to add the problem that alloying elements such as Ca, Sr, P or Sb bring again, make the Mg-Al-Si series magnesium alloy can be used for technologies such as gravitational casting and sand mold casting, enlarged the range of application of Mg-Al-Si series magnesium alloy.

Description of drawings

Fig. 1 is the temperature-timing relationship synoptic diagram of the isothermal heat treatment method that proposes of the present invention;

Fig. 2 is the metallographic structure figure of the alloy that obtains of embodiment 1;

Fig. 3 is the metallographic structure figure of the alloy that obtains of embodiment 2;

Fig. 4 is the metallographic structure figure of the alloy that obtains of embodiment 3.

Embodiment:

Below by three concrete embodiment implementing process of the present invention and effect are further elaborated.

Embodiment 1:Mg-4Al-1Si alloy

Implementation process: press Mg-4Al-1Si alloying constituent configuration alloy and with its fusing; when temperature is raised to 740 ℃; drag for alloy liquid surface scum; carry out gravitational casting then; in the gravitational casting process when alloy is cooled to 415 ℃; alloy is put into the chamber type electric resistance furnace insulation 20 hours that rises to 415 ℃ and protective atmosphere is arranged, from resistance furnace, take out in the entry of quenching fast then.The alloy that adopts proposition method of the present invention to obtain is made metallographic structure analysis, and the result as shown in Figure 2.As we can see from the figure, adopt proposition method of the present invention to handle alloy after, the Chinese character shape Mg in the alloy structure ₂Si is not fairly obvious mutually, and the method processing gravitational casting Mg-4Al-1Si alloy that adopts the present invention to propose is described, can make the Chinese character shape Mg in the alloy structure ₂Si is rotten mutually.

Embodiment 2:Mg-6Al-1Si alloy

Implementation process: press Mg-6Al-1Si alloying constituent configuration alloy and with its fusing; when temperature is raised to 720 ℃; drag for alloy liquid surface scum; carry out gravitational casting then; in sand casting process when alloy is cooled to 420 ℃; with alloy put into rise to 420 ℃ and have protective atmosphere chamber type electric resistance furnace insulation 16 hours, from resistance furnace, take out in the entry of quenching fast then.The alloy that adopts proposition method of the present invention to obtain is made metallographic structure analysis, and the result as shown in Figure 3.As we can see from the figure, adopt proposition method of the present invention to handle alloy after, the Chinese character shape Mg in the alloy structure ₂Si is not fairly obvious mutually, and the method processing sand mold casting Mg-6Al-1Si alloy that adopts the present invention to propose is described, can make the Chinese character shape Mg in the alloy structure ₂Si is rotten mutually.

Embodiment 3:Mg-6Al-1Si-1Zn alloy

Implementation process: press Mg-6Al-1Si-1Zn alloying constituent configuration alloy and with its fusing; when temperature is raised to 730 ℃; drag for alloy liquid surface scum; carry out gravitational casting then; in the gravitational casting process when alloy is cooled to 425 ℃; with alloy put into rise to 425 ℃ and have protective atmosphere chamber type electric resistance furnace insulation 14 hours, from resistance furnace, take out in the entry of quenching fast then.The alloy that adopts proposition method of the present invention to obtain is made metallographic structure analysis, and the result as shown in Figure 4.As we can see from the figure, adopt proposition method of the present invention to handle alloy after, the Chinese character shape Mg in the alloy structure ₂Si is not fairly obvious mutually, and the method processing gravitational casting Mg-6Al-1Si-1Zn alloy that adopts the present invention to propose is described, can make the Chinese character shape Mg in the alloy structure ₂Si is rotten mutually.

Claims

1. be used for rotten Mg-Al-Si series magnesium alloy Chinese character shape Mg ₂The isothermal heat treatment method of Si phase; it is characterized in that: be warmed up to 720～740 ℃ after the Mg-Al-Si series magnesium alloy is melted by composition proportion; drag for alloy liquid surface scum; carry out gravitational casting or sand mold casting then; in castingprocesses after the temperature of alloy drops to solid solution temperature below the solidus temperature; alloy is incubated 12-24 hour under protective atmosphere, takes out in the entry of quenching fast then.