Method for promoting densification of metal body by utilizing metal expansion induced by hydrogen absorption

Abstract

Provided is a method for promoting densification of a metal body by utilizing metal expansion induced by hydrogen absorption. The hydrogen absorption expansion refers to a volume expansion effect produced by absorbing hydrogen on some metal blocks or metal powder in a hydrogen atmosphere under certain temperature conditions. Hydrogen is introduced into a rigid closed mold filled with a hydrogen absorption expansion material or filled with the hydrogen absorption expansion material and a material to be densified, and the mold and/or the material to be densified are/is densified by using the volume expansion effect of the hydrogen absorption expansion material. The present method may be used for eliminating residual pores from a metal material so as to improve the properties of the material.

Claims

1. A method for promoting densification of a metal body by utilizing metal expansion induced by hydrogen absorption, wherein hydrogen is introduced into a rigid closed mold filled with a hydrogen absorption expansion material or filled with the hydrogen absorption expansion material and a metal material to be densified, and a volume expansion effect of the hydrogen absorption expansion material is used to densify the hydrogen absorption expansion material and/or the metal material to be densified; wherein the method comprises the following steps: step 1: putting a first pre-densified metal body into the rigid closed mold, performing encapsulation and fastening, and reserving a gas opening to obtain a pretreatment assembly, wherein the first pre-densified metal body comprises a metal material with hydrogen absorption capability; in the pretreatment assembly, an outer wall of the first pre-densified metal body is in contact with an inner wall of the rigid closed mold, or a gap exists between the outer wall of the first pre-densified metal body and the inner wall of the rigid closed mold; and the gap is smaller than a linear expansion after the first pre-densified metal body absorbs hydrogen, or charging a second pre-densified metal body and a hydrogen absorbable metal powder into the rigid closed mold together, performing encapsulation and fastening, and reserving the gas opening to obtain the pretreatment assembly, or putting the metal material to be densified onto a set position of a mold inner cavity, putting the hydrogen absorbable metal powder onto other positions of the mold inner cavity, performing encapsulation and fastening, and reserving the gas opening to obtain the pretreatment assembly; step 2: putting the pretreatment assembly obtained in the step 1 into a sintering furnace, introducing hydrogen, raising a temperature to a hydrogen absorption temperature, and performing heat soaking to obtain a hydrogenated assembly: then, regulating an atmosphere into an inert atmosphere or a vacuum atmosphere and/or performing heat soaking at a dehydrogenation temperature so that the hydrogenated assembly releases hydrogen to obtain a dehydrogenated assembly; and step 3: after the dehydrogenated assembly is cooled, removing the rigid closed mold to obtain a densified metal body.

2. The method for promoting densification of the metal body according to claim 1, wherein the hydrogen absorption expansion material comprises a metal with hydrogen absorption capability.

3. The method for promoting densification of the metal body according to claim 1, wherein throughout step 2, the rigid closed mold keeps the pretreatment assembly tight and firm without loosening.

4. The method for promoting densification of the metal body according to claim 1, wherein after complete hydrogen absorption by the metal material with hydrogen absorption capability or the hydrogen absorbable metal powder, a volume of the first pre-densified metal body or the hydrogen absorbable metal powder realizes at least more than 5 vol % expansion compared with a volume of the first pre-densified metal body or the hydrogen absorbable metal powder before the hydrogen absorption.

5. The method for promoting densification of the metal body according to claim 1, wherein a material of the rigid closed mold does not react with hydrogen.

6. The method for promoting densification of the metal body according to claim 1, wherein the metal material with hydrogen absorption capability or the hydrogen absorbable metal powder absorbs hydrogen at the hydrogen absorption temperature under a condition that a hydrogen partial pressure is greater than or equal to a hydrogen equilibrium partial pressure of the metal material with hydrogen absorption capability or the hydrogen absorbable metal powder, the hydrogen absorption temperature is determined by physicochemical properties of the metal material with hydrogen absorption capability and/or the hydrogen absorbable metal powder.

7. The method for promoting densification of the metal body according to claim 1, wherein the metal material with hydrogen absorption capability and/or the hydrogen absorbable metal powder comprise/comprises at least one element of Ti, Mg, Zr, V, Nb, Ta, Pd and rare earth elements.

8. The method for promoting densification of the metal body according to claim 1, wherein step 2 is repeated until a product with a set density is obtained.

9. The method for promoting densification of the metal body according to claim 1, wherein the steps 1, 2 and 3 are sequentially repeated until a product with a set density is obtained.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1A-1B show schematic diagrams of a work principle of the present invention. FIG. 1A shows an assembled mold before the heating and hydrogen introduction. FIG. 1B shows an assembled mold after hydrogen is introduced.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(2) The present invention will be further illustrated in detail in conjunction with embodiments hereafter.

(3) In the present invention, an encapsulated mold cannot generate component loosening and falling in a heating process.

Embodiment 1

(4) 1. A titanium product with a density of 98% (industrial pure titanium, titanium content>98%) was put into a stainless steel mold. Titanium powder with an average size of 45 μm (a filling volume of the titanium powder accounts for 40% of a volume of a mold inner cavity) was fully filled between the product and the mold. The mold was encapsulated and fastened. (Gaps existed between mold modules, and these gaps were good vent holes).

(5) 2. The assembled mold was put into a hydrogen furnace, and was heated to 600° C. in vacuum. Hydrogen (the pressure of the hydrogen was 1 bar) was introduced. Hydrogen introduction was maintained. Heat soaking was performed for 10 h.

(6) 3. Hydrogen introduction into the hydrogen furnace was stopped. Vacuum pumping was performed (a vacuum degree was less than 10.sup.−3 Pa). A temperature was raised to 750° C. After soaking for 10 h, furnace shut down for cooling was performed.

(7) 4. The hydrogen furnace was opened. The mold was taken out and opened. A titanium alloy product with a density of higher than 99.5% was taken out.

Comparative Example 1

(8) Other conditions were all identical to those of Embodiment 1. The difference was that in the step (2), argon was introduced instead of hydrogen. The density of the obtained product had no obvious change.

Embodiment 2

(9) 1. A titanium product with a density of 95% (titanium content>20%) was put into a stainless steel mold. Fit between the product and the mold was smaller than 0.1 mm. The mold was encapsulated and fastened. (Gaps existed between mold modules, and these gaps were good vent holes).

(10) 2. The assembled mold was put into a hydrogen furnace, and was heated to 600° C. in vacuum. Hydrogen (the pressure of the hydrogen was 10 bar) was introduced. Hydrogen introduction was maintained. Heat soaking was performed for 10 h.

(11) 3. Hydrogen introduction into the hydrogen furnace was stopped. Vacuum pumping was performed (a vacuum degree was less than 10.sup.−3 Pa). A temperature was raised to 750° C. After soaking for 10 h, furnace shut down for cooling was performed.

(12) 4. The hydrogen furnace was opened. The mold was taken out and opened. A titanium alloy product with a density of higher than 99.5% was taken out.

Comparative Example 2

(13) Other conditions were all identical to those of Embodiment 2. The difference was that in the step (2), argon was introduced instead of hydrogen. The density of the obtained product had no change.

Embodiment 3

(14) 1. A copper alloy product with a density of 95% (copper content>60%) was put into a stainless steel mold. Titanium powder with an average size of 45 μm (a filling volume of the titanium powder accounts for 30% of a volume of a mold inner cavity) was filled between the product and the mold. The mold was encapsulated and fastened. (Gaps existed between mold modules, and these gaps were good vent holes).

(15) 2. The assembled mold was put into a hydrogen furnace, and was heated to 600° C. in vacuum. Hydrogen (the pressure of the hydrogen was 1 bar) was introduced. Hydrogen introduction was maintained. Heat soaking was performed for 10 h.

(16) 3. Hydrogen introduction into the hydrogen furnace was stopped. Vacuum pumping was performed (a vacuum degree was less than 10.sup.−3 Pa). A temperature was raised to 750° C. After soaking for 10 h, furnace shut down for cooling was performed.

(17) 4. The hydrogen furnace was opened. The mold was taken out and opened. A copper alloy product with the density of higher than 99% was taken out.

Comparative Example 3

(18) Other conditions were all identical to those of Embodiment 3. The difference was that in the step (2), argon was introduced instead of hydrogen. The density of the obtained product had no change.

Embodiment 4

(19) 1. A stainless steel mold was fully filled with titanium alloy powder with an average size of 45 μm (ingredient: Ti-6Al-4V). The mold was encapsulated and fastened. (Gaps existed between mold modules, and these gaps were good vent holes).

(20) 2. The assembled mold was put into a hydrogen furnace, and was heated to 600° C. in vacuum. Hydrogen (the pressure of the hydrogen was 1 bar) was introduced. Hydrogen introduction was maintained. Heat soaking was performed for 10 h.

(21) 3. Hydrogen introduction into the hydrogen furnace was stopped. Vacuum pumping was performed (a vacuum degree was less than 10.sup.−3 Pa). A temperature was raised to 750° C. After soaking for 10 h, furnace shut down for cooling was performed.

(22) 4. The hydrogen furnace was opened. The mold was taken out and opened. A titanium alloy product with a density of higher than 80% was taken out.

Comparative Example 4

(23) Other conditions were all identical to those of Embodiment 4. The difference was that in the step (2), argon was introduced instead of hydrogen. The density of the obtained product had no obvious change.

Embodiment 5

(24) 1. An aluminum alloy product with a density of 95% (aluminum content>90%) was put into a stainless steel mold. ZrNi alloy powder with an average size of 60 μm (a filling volume of the ZrNi alloy powder accounts for 40% of a volume of a mold inner cavity) was filled between the product and the mold. The mold was sealed.

(25) 2. The assembled mold was put into a hydrogen furnace, and was heated to 200° C. in hydrogen. Hydrogen (the pressure of the hydrogen was 1 bar) was introduced. Heat soaking was performed for 5 h.

(26) 3. Hydrogen introduction into the hydrogen furnace was stopped. Vacuum pumping was performed (a vacuum degree was less than 10.sup.−3 Pa). A temperature was raised to 300° C. After soaking for 1 h, furnace shut down for cooling was performed.

(27) 4. The hydrogen furnace was opened. The mold was taken out and opened. An aluminum alloy product with a density of higher than 99% was taken out.

Comparative Example 5

(28) Other conditions were all identical to those of Embodiment 5. The difference was that in the step (2), argon was introduced instead of hydrogen. The density of the obtained product had no change.