CN101818314A - Method for enhancing mechanical property of AZ91D magnesium alloy - Google Patents

Abstract

The invention discloses a method for enhancing the mechanical property of an AZ91D magnesium alloy, and aims to improve the comprehensive mechanical property of an AZ91D composite material. The preparation method comprises the following steps of: preparing carbon nano tubes by using an anodic arc plasma method; purifying, sensitizing and activating the carbon nano tubes and plating nickel on the carbon nano tubes; placing the AZ91D in a cast-iron crucible at 720 DEG C under an as-cast condition, melting the AZ91D, adding CNTs and SiCp into the molten AZ91D and stirring the mixture for 5 minutes; and casting, solidifying and stripping the mould. The modulus of elasticity, hardness, tensile strength and elongation of the composite material are improved by 29.8 percent, 9.39 percent, 46.77 percent and 14.69 percent respectively by grain refinement and dislocation strengthening.

Description

A kind of method that strengthens the AZ91D magnesium alloy mechanical property

Technical field

The present invention relates to the technology of preparing of metal-base composites.

Background technology

The AZ91D magnesium alloy be develop the earliest, one of most widely used magnesium alloy, have advantages such as density is little, specific tenacity is big, damping and amortization is good, thermal conductivity is good, be used widely at industrial circles such as automobile, electronics, electrical equipment.But the AZ91D magnesium alloy also has the shortcoming of following several respects: intensity is not high, plastic making is poor, can't be made into the high strength structure material in the industrial application, and the casting forming method also has limitation, has hindered AZ91D Application of Magnesium and development.

Summary of the invention

The objective of the invention is to improve the comprehensive mechanical property of AZ91D matrix material.

The present invention is a kind of method of the AZ91D of enhancing magnesium alloy mechanical property, the steps include:

(1) adopt the anode arc plasma method to prepare carbon nanotube (CNTs):

1. carbon nanotube is put into dense HNO ₃With dense H ₂SO ₄Soaked 24 hours in the mixing acid of preparation in 1: 3 by volume, use deionized water rinsing, left standstill 4 hours, collect supernatant liquor, wash several times repeatedly, up to pH=7, supernatant liquor all collected to leave standstill made its precipitation in 24 hours, then throw out suction filtration and oven dry;

2. the throw out of oven dry is put into SnCl ₂2H ₂O:20g/L, sensitization in the sensitizing solution of HCl:40g/L makes SnCl ₂Be deposited on the surface of carbon nanotube, solution is washed behind pH=7 repeatedly with its oven dry;

3. put it into PdCl ₂: 0.5g/L, left standstill in the activation solution of HCl:40g/L 10 minutes, washing is repeatedly dried behind pH=7 then;

4. magnetic agitation is 10 minutes in the plating bath that puts it into again, and ultrasonic then concussion was washed after 30 minutes, dried behind pH=7; The composition of plating bath and concentration are: NiSO ₄: 40g/L, Na ₃C ₆H ₅O ₇: 50g/L and NaH ₂PO ₂: 40g/L;

5. at last the carbon nanotube behind the plating is put into vacuum tube furnace and heat-treat, temperature is 400 ℃, and the time is 3 hours;

(2) as cast condition AZ91D is put into cast-iron pot in the heating of the smelting furnace of applying argon gas and under 720 ℃ of temperature, melt.

(3) putting into mortar before CNTs and SiCp add ground 20 minutes; Nickel plating CNTs and SiCp joined in the crucible stir, churning time is 5 minutes, percentage ratio meter by volume, and the content of CNTs and SiCp is respectively 1.0% and 3.0%, and the volume fraction of AZ91D matrix is 96.0%;

(4) leave standstill 1 minute, when treating that furnace temperature rises to 720 ℃, cast, carry out molding after solidifying; Before casting, put cleaning and exsiccant mould in another stove that is heated to 300 ℃ preheating, and be coated with the very thin ZnO of last layer at die surface.

Usefulness of the present invention is: when the present invention improved the intensity of AZ91D matrix material and hardness, its unit elongation also was improved.The Young's modulus of matrix material, Brinell hardness, tensile strength, unit elongation have improved 29.8%, 9.39%, 46.77%, 14.69% than AZ91D body material respectively.

Description of drawings

Fig. 1 is the metallograph of AZ91D matrix material, and Fig. 2 is the metallograph of CNTs/SiCp/AZ91D matrix material.

Embodiment

The present invention is a kind of method of the AZ91D of enhancing magnesium alloy mechanical property, the steps include:

(1) adopt the anode arc plasma method to prepare carbon nanotube (CNTs):

1. carbon nanotube is put into dense HNO ₃With dense H ₂SO ₄Soaked 24 hours in the mixing acid of preparation in 1: 3 by volume, use deionized water rinsing, left standstill 4 hours, collect supernatant liquor, wash several times repeatedly, up to pH=7, supernatant liquor all collected to leave standstill made its precipitation in 24 hours, then throw out suction filtration and oven dry;

2. the throw out of oven dry is put into SnCl ₂2H ₂O:20g/L, sensitization in the sensitizing solution of HCl:40g/L makes SnCl ₂Be deposited on the surface of carbon nanotube, solution is washed behind pH=7 repeatedly with its oven dry;

3. put it into PdCl ₂: 0.5g/L, left standstill in the activation solution of HCl:40g/L 10 minutes, washing is repeatedly dried behind pH=7 then;

4. magnetic agitation is 10 minutes in the plating bath that puts it into again, and ultrasonic then concussion was washed after 30 minutes, dried behind pH=7; The composition of plating bath and concentration are: NiSO ₄: 40g/L, Na ₃C ₆H ₅O ₇: 50g/L and NaH ₂PO ₂: 40g/L;

5. at last the carbon nanotube behind the plating is put into vacuum tube furnace and heat-treat, temperature is 400 ℃, and the time is 3 hours;

(2) as cast condition AZ91D is put into cast-iron pot in the heating of the smelting furnace of applying argon gas and under 720 ℃ of temperature, melt.

(3) putting into mortar before CNTs and SiCp add ground 20 minutes; Nickel plating CNTs and SiCp joined in the crucible stir, churning time is 5 minutes, percentage ratio meter by volume, and the content of CNTs and SiCp is respectively 1.0% and 3.0%, and the volume fraction of AZ91D matrix is 96.0%;

(4) leave standstill 1 minute, when treating that furnace temperature rises to 720 ℃, cast, carry out molding after solidifying; Before casting, put cleaning and exsiccant mould in another stove that is heated to 300 ℃ preheating, and be coated with the very thin ZnO of last layer at die surface.

Optimal processing parameter is: whipping temp is 720 ℃, and churning time is 5 minutes.When the content of CNTs and SiCp is respectively 1.0vol% and 3.0vol%, the comprehensive mechanical property of matrix material is best, under this material mixture ratio (1.0vol%CNTs/3.0vol%SiCp/AZ91D), AZ91D compares with body material, the Young's modulus of matrix material 1.0vol%CNTs/3.0vol%SiCp/AZ91D, hardness, tensile strength and unit elongation are respectively 56.61Gpa, 65.14 individual Brinell hardness, 278.84MP with 3.899%, than body material AZ91D (Young's modulus 43.61Gpa, hardness 59.55, tensile strength 189.98MP and unit elongation 3.40%) improved 29.8% respectively, 9.39%, 46.77% and 14.69%.

As shown in Figure 1, mainly comprise two kinds in the tissue of as cast condition AZ91D, a kind of is the α-Mg that exists with white crystal grain form, exists with a large amount of dentrite forms; Another kind is the β-Mg that separates out at the crystal boundary place ₁₇Al ₁₂, and be continuous net-shaped distribution.As shown in Figure 2, behind adding CNTs and the SiCp wild phase, be the β-Mg of continuous net-shaped distribution originally ₁₇Al ₁₂Become suspension and distribute, the effect of crystal grain that refinement has been played in the adding that CNTs and SiCp be described.

There are a large amount of CNTs, SiCp in the AZ91D alloy substrate, the very big (CTE=26 of Mg * 10 of thermal expansivity (CTE) difference of they and matrix ^-6/ ℃, the CTE=4 of SiCp * 10 ^-6/ ℃, the CTE ≈ 0 of CNTs), in the cooled and solidified process of matrix material, the shrinkage of wild phase and matrix is different, thereby produces highdensity dislocation near CNTs, SiCp, emits a series of dislocation loop, along with the increasing and become big of dislocation loop, the stress field of dislocation loop increases.After stress field increases to a certain degree, will hinder the slippage of dislocation, so produced dislocations strengthening, make the intensity of matrix increase.The acting in conjunction of refined crystalline strengthening, dislocations strengthening is improved the mechanical property of matrix material largely.

Nickel plating CNTs has increased the consistency between CNTs and the AZ91D alloy substrate.

CNTs has high tensile strength and Young's modulus, and the hardness of SiCp is bigger, realizes having complementary advantages in metallic matrix, has played the effect of carrying plus load and stress transfer.

Put into mortar before CNTs and SiCp add and ground 20 minutes, improved the dispersiveness of CNTs in matrix.

Because the toughness of CNTs is fine, in addition, after grain refining, improved the probability that the distortion of crystal grain inside is coordinated towards periphery, finally improve the plasticity of matrix material, the unit elongation of matrix material is improved.

Claims (1)

1. a method that strengthens the AZ91D magnesium alloy mechanical property the steps include:

(1) adopt the anode arc plasma method to prepare carbon nanotube:

1. carbon nanotube is put into dense HNO ₃With dense H ₂SO ₄Soaked 24 hours in the mixing acid of preparation in 1: 3 by volume, use deionized water rinsing, left standstill 4 hours, collect supernatant liquor, wash several times repeatedly, up to pH=7, supernatant liquor all collected to leave standstill made its precipitation in 24 hours, then throw out suction filtration and oven dry;

2. the throw out of oven dry is put into SnCl ₂2H ₂O:20g/L, sensitization in the sensitizing solution of HCl:40g/L makes SnCl ₂Be deposited on the surface of carbon nanotube, solution is washed behind pH=7 repeatedly with its oven dry;

3. put it into PdCl ₂: 0.5g/L, left standstill in the activation solution of HCl:40g/L 10 minutes, washing is repeatedly dried behind pH=7 then;

4. magnetic agitation is 10 minutes in the plating bath that puts it into again, and ultrasonic then concussion was washed after 30 minutes, dried behind pH=7; The composition of plating bath and concentration are: NiSO ₄: 40g/L, Na ₃C ₆H ₅O ₇: 50g/L and NaH ₂PO ₂: 40g/L;

5. at last the carbon nanotube behind the plating is put into vacuum tube furnace and heat-treat, temperature is 400 ℃, and the time is 3 hours;

(2) as cast condition AZ91D is put into cast-iron pot in the heating of the smelting furnace of applying argon gas and under 720 ℃ of temperature, melt;

(3) putting into mortar before CNTs and SiCp add ground 20 minutes; Nickel plating CNTs and SiCp joined in the crucible stir, churning time is 5 minutes, percentage ratio meter by volume, and the content of CNTs and SiCp is respectively 1.0% and 3.0%, and the volume fraction of AZ91D matrix is 96.0%;

(4) leave standstill 1 minute, when treating that furnace temperature rises to 720 ℃, cast, carry out molding after solidifying; Before casting, put cleaning and exsiccant mould in another stove that is heated to 300 ℃ preheating, and be coated with the very thin ZnO of last layer at die surface.

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