Fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy and preparation method thereof

Abstract

The present invention discloses a fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy and a preparation method, specifically: Cu powder, Sn powder, and Ti powder are ball-milled and mixed, the mixed powder is evenly filled into a rubber sleeve for sealing and vacuum degassing, cold isostatic pressing is performed, and the obtained Cu-15Sn-0.3Ti alloy cold-pressed billet is vacuum hot-pressed and sintered to obtain a Cu-15Sn-0.3Ti alloy test bar; the Cu-15Sn-0.3Ti alloy test bar is hot-extruded, solution-treated, and water-quenched. The Cu-15Sn-0.3Ti alloy prepared by this method has a uniform structure and a minimum average grain size of 7.38 μm, and the alloy has a density of up to 99.73%, a conductivity of up to 4.24 MS / m, a hardness of up to 91.8 HB, and a plasticity of up to 53.67%.

Description

Technical Field

[0001] The invention belongs to the technical field of powder metallurgy, and in particular relates to a method for preparing a fine-grained, high-plasticity, and high-density Cu-15Sn-0.3Ti alloy, and also relates to a fine-grained, high-plasticity, and high-density Cu-15Sn-0.3Ti alloy. Background Art

[0002] At present, Nb3Sn superconducting wire has a high critical current density J C It is widely used in superconducting fields such as medical nuclear magnetic resonance (NMR) and the Large Hadron Collider (LHC) at home and abroad. Cu-15Sn-0.3Ti alloy is the production base material of Nb3Sn superconducting wire. Its Sn content and plasticity respectively restrict the critical current density and long wire preparation of Nb3Sn superconducting wire.

[0003] At present, traditional powder metallurgy is one of the main methods for preparing Cu-15Sn-0.3Ti alloy. This method is to mix Cu powder, Sn powder and Ti powder uniformly and then sinter them under pressureless sintering to obtain Cu-15Sn-0.3Ti alloy. However, this method still has the following problems: 1. The grain size of Cu-15Sn-0.3Ti alloy is larger than 300μm and the grains are coarse; 2. The hard and brittle δ-Cu in Cu-15Sn-0.3Ti alloy is not good. 41 Sn 11 The phase is severely segregated in the structure and is large in size, greater than 50μm; 3. The density of Cu-15Sn-0.3Ti alloy is low, less than 96.4%; 4. The plasticity of Cu-15Sn-0.3Ti alloy is poor, not exceeding 30%. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a fine-grained, high-plasticity, and high-density Cu-15Sn-0.3Ti alloy, which solves the problems of coarse grain size and low density of the Cu-15Sn-0.3Ti alloy prepared by the existing method.

[0005] Another object of the present invention is to provide the above-mentioned fine-grained, high-plasticity, and high-density Cu-15Sn-0.3Ti alloy.

[0006] The technical solution adopted by the present invention is a method for preparing a fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy, which is specifically implemented according to the following steps:

[0007] Step 1: ball-mill Cu powder, Sn powder and Ti powder in proportion to obtain mixed powder;

[0008] Step 2: The mixed powder is evenly filled into a rubber sleeve for sealing and vacuum degassing, and the sleeve is placed in a cold isostatic press for cold isostatic pressing to obtain a Cu-15Sn-0.3Ti alloy cold pressed billet;

[0009] Step 3: placing the Cu-15Sn-0.3Ti alloy cold pressed blank into a vacuum hot pressing sintering furnace for vacuum hot pressing sintering to obtain a Cu-15Sn-0.3Ti alloy test bar;

[0010] Step 4: hot extruding the Cu-15Sn-0.3Ti alloy test bar to obtain a hot-extruded Cu-15Sn-0.3Ti alloy bar;

[0011] Step 5: The hot-extruded Cu-15Sn-0.3Ti alloy rod is solution treated and water quenched to obtain a fine-grained, high-plasticity, and high-density Cu-15Sn-0.3Ti alloy.

[0012] The present invention is also characterized in that:

[0013] In step 1, the mixed powder includes, by mass percentage, 84.7% Cu powder, 15% Sn powder, and 0.3% Ti powder, and the sum of the components is 100%.

[0014] In step 1, during ball milling: control the ball mill speed to 120-180 r / min, the forward and reverse rotation time to 10-18 min, and the powder mixing time to 12-24 h.

[0015] In step 2, during the cold isostatic pressing treatment, the pressing force is controlled to be 180±10 MPa, the pressure increase rate is 10-18 MPa / min, and the holding time is 10±5 min.

[0016] In step 3, during vacuum hot pressing sintering, the vacuum degree in the furnace is reduced to 6.8×10 -3 Pa, first, the temperature was increased from room temperature to 550°C at a heating rate of 15.5°C / min, and the pressure was increased to 20MPa at a heating rate of 2MPa / min, and then kept warm and pressurized for 20min. Secondly, the temperature was increased to 700-725°C at a heating rate of 7.5°C / min, and the pressure was increased to 30MPa at a heating rate of 1MPa / min, and then kept warm and pressurized for 120min, and then slowly cooled with the furnace. When the temperature was reduced to 400°C, the pressure was reduced at a rate of 0.2MPa / min, and finally the Cu-15Sn-0.3Ti alloy test bar after vacuum hot pressing sintering was obtained.

[0017] In step 4, specifically:

[0018] The Cu-15Sn-0.3Ti alloy rod after vacuum hot pressing sintering was placed in a copper sleeve, and a copper cover was matched with the copper sleeve and vacuum diffusion welding was performed to make the Cu-15Sn-0.3Ti alloy test rod tightly wrapped by the copper sleeve as a whole. The whole was placed in a nitrogen heating furnace with a holding temperature of 600-650°C for softening treatment for 120±5min. After the holding period, it was immediately placed in an extrusion barrel preheated to 400°C for hot extrusion treatment to obtain a hot-extruded Cu-15Sn-0.3Ti alloy rod.

[0019] During hot extrusion treatment: control the extrusion pressure to be no less than 4500KN, the extrusion rate to be 10-20mm / s, and the extrusion ratio to be 12:1.

[0020] In step 5, the solution treatment temperature is 550-600° C., and the solution treatment time is 80 h.

[0021] Another technical solution adopted by the present invention is that a fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy is prepared by the above method.

[0022] The beneficial effects of the present invention are:

[0023] The preparation method of the fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy of the present invention is to perform vacuum hot pressing sintering on the cold pressed blank of the Cu-15Sn-0.3Ti alloy prepared by the cold isostatic pressing process. The heat-mechanical synergy can reduce the vacuum hot pressing sintering temperature, thereby inhibiting grain growth; the temperature is kept at 550°C for 20 minutes, which promotes the diffusion of Sn in the alloy into Cu; after cooling to 400°C, the pressure is reduced, which slows down the dimensional expansion of the alloy caused by internal stress after unloading at high temperature, thereby improving the density of the alloy. The vacuum hot pressed sintered Cu-15Sn-0.3Ti alloy is subjected to hot extrusion treatment. The larger extrusion pressure and faster extrusion rate improve the δ-Cu in the Cu-15Sn-0.3Ti alloy. 41 Sn 11 The alloy undergoes dynamic recovery recrystallization by extruding in an extrusion barrel preheated to 400°C. During this process, a large number of coarse α-Cu grains are transformed into fine equiaxed grains, improving the alloy's structural uniformity and enhancing its plasticity. The Cu-15Sn-0.3Ti alloy prepared using this method exhibits a uniform microstructure with an average grain size as small as 7.38μm. Furthermore, the alloy boasts a density of 99.73%, a maximum electrical conductivity of 4.24MS / m, a hardness of 91.8HB, and a plasticity of 53.67%. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1is a microstructure photograph of the fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy in Example 4;

[0025] Figure 2 is a stress-strain curve diagram of the Cu-15Sn-0.3Ti alloy in Examples 1-5;

[0026] Figure 3 is a density test diagram of the Cu-15Sn-0.3Ti alloy in Examples 1-5;

[0027] Figure 4 is a graph showing the electrical conductivity and hardness of the Cu-15Sn-0.3Ti alloy in Examples 1-5;

[0028] Figure 5 is a graph of the average grain size of the Cu-15Sn-0.3Ti alloy in Examples 1-5. DETAILED DESCRIPTION

[0029] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] The preparation method of the fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy of the present invention comprises the following steps: firstly, Cu powder, Sn powder, and Ti powder are uniformly mixed in proportion by ball milling; secondly, the uniformly mixed metal powders are cold isostatically pressed; and then, the Cu-15Sn-0.3Ti alloy is prepared by vacuum hot pressing and sintering; and finally, the vacuum hot pressed and sintered alloy is hot extruded; and finally, the hot-extruded alloy is solution treated to obtain the fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy.

[0031] Please follow the steps below to implement:

[0032] Step 1: Mix Cu powder, Sn powder and Ti powder in proportion to obtain mixed powder;

[0033] Weigh 84.7% Cu powder, 15% Sn powder, and 0.3% Ti powder by mass, with the sum of the components being 100%, and ball mill to obtain a mixed powder;

[0034] During ball milling: control the ball mill speed to 120-180r / min, the forward and reverse rotation time to 10-18min, and the powder mixing time to 12-24h;

[0035] Step 2: The mixed powder is evenly filled into the rubber sleeve for sealing and vacuum degassing, and the sleeve is placed in a cold isostatic press. The pressing force is controlled to be 180±10MPa, the pressure increase rate is 10-18MPa / min, and the pressure holding time is 10±5min. After unloading, the Cu-15Sn-0.3Ti alloy cold pressed billet is taken out;

[0036] Step 3: placing the Cu-15Sn-0.3Ti alloy cold pressed blank into a vacuum hot pressing sintering furnace for vacuum hot pressing sintering to obtain a Cu-15Sn-0.3Ti alloy test bar;

[0037] During vacuum hot pressing sintering: the vacuum degree in the furnace is reduced to 6.8×10 -3 Pa below, firstly, the temperature was increased from room temperature to 550°C at a heating rate of 15.5°C / min, and at the same time, the pressure was increased to 20MPa at a heating rate of 2MPa / min, and then the temperature was kept at 20MPa for 20min, then the temperature was increased to 700-725°C at a heating rate of 7.5°C / min, and at the same time, the pressure was increased to 30MPa at a heating rate of 1MPa / min, and the temperature was kept at 30MPa for 120min, then the temperature was slowly cooled with the furnace, and when the temperature was reduced to 400°C, the pressure was reduced at a rate of 0.2MPa / min, and finally a Cu-15Sn-0.3Ti alloy test bar after vacuum hot pressing sintering was obtained;

[0038] Step 4: hot extrusion treatment of the Cu-15Sn-0.3Ti alloy test bar; specifically:

[0039] The vacuum hot-pressed Cu-15Sn-0.3Ti alloy rod is placed in a copper sleeve, and a copper cover is matched with the copper sleeve and vacuum diffusion welding is performed to tightly wrap the Cu-15Sn-0.3Ti alloy rod into a whole. The whole rod is placed in a nitrogen heating furnace at a holding temperature of 600-650°C for a holding time of 120±5 minutes for softening treatment. After the holding period, the rod is immediately placed in an extrusion barrel preheated to 400°C for hot extrusion treatment to obtain a hot-extruded Cu-15Sn-0.3Ti alloy rod.

[0040] During hot extrusion treatment: control the extrusion pressure to be no less than 4500KN, the extrusion rate to be 10-20mm / s, and the extrusion ratio to be 12:1;

[0041] The diameter d of the hot-extruded Cu-15Sn-0.3Ti alloy rod is 18 mm;

[0042] The diameter of the copper sheath is D = 68 mm, the internal aperture d1 is 62 mm, and the length L is 100 mm; the thickness of the copper cover is h 10 mm;

[0043] Step 5: The hot-extruded Cu-15Sn-0.3Ti alloy rod is solution treated in a box-type resistance furnace at a temperature of 550-600°C for 80 hours. After the treatment, it is water quenched to obtain a fine-grained, high-plasticity, and high-density Cu-15Sn-0.3Ti alloy.

[0044] The cold pressed Cu-15Sn-0.3Ti alloy blank prepared by cold isostatic pressing was subjected to vacuum hot pressing sintering. The lower vacuum hot pressing sintering temperature inhibited the growth of grains, promoted the diffusion of Sn into Cu, and improved the density of the alloy. The vacuum hot pressing sintered Cu-15Sn-0.3Ti alloy was subjected to hot extrusion treatment. The larger extrusion pressure and faster extrusion rate improved the δ-Cu in the Cu-15Sn-0.3Ti alloy. 41 Sn 11 The size and distribution of the phase cause the alloy to undergo dynamic recovery recrystallization. A large number of coarse α-Cu grains are transformed into fine equiaxed grains in this process, which improves the structural uniformity of the alloy and enhances the plasticity of the alloy.

[0045] The preparation method of the fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy of the present invention adopts vacuum hot pressing sintering and hot extrusion treatment to solve the problems of the existing method in that the Cu-15Sn-0.3Ti alloy has coarse grains and Cu 41 Sn 11 The Cu-15Sn-0.3Ti alloy prepared by this method has a uniform structure and a minimum average grain size of 7.38μm. The Cu-15Sn-0.3Ti alloy has a density of up to 99.73%, a conductivity of up to 4.24MS / m, a hardness of up to 91.8HB, and a plasticity of up to 53.67%.

[0046] Example 1

[0047] The preparation method of the Cu-15Sn-0.3Ti alloy test bar is as follows:

[0048] Weigh 84.7% Cu powder, 15% Sn powder, and 0.3% Ti powder, and mix them in a ball mill mixer. Control the ball mill speed to 120r / min, the forward and reverse rotation time to 10min, and the mixing time to 12h.

[0049] Weigh 2680g of the uniformly mixed Cu powder, Sn powder, and Ti powder, and evenly fill them into the rubber bag for sealing and vacuum degassing. Place the bag in a cold isostatic press, control the pressing force to 180MPa, the pressure increase rate to 15MPa / min, the holding time to 10min, and take out the cold pressed billet after unloading.

[0050] The Cu-15Sn-0.3Ti alloy cold pressed billet was placed in a vacuum hot pressing sintering furnace and the vacuum degree in the furnace was reduced to 6.8×10 -3Pa below, first from room temperature to 550 ℃ at a heating rate of 15.5 ℃ / min, while the pressure was increased to 20 MPa at a rate of 2 MPa / min and then kept at this temperature and pressure for 20 min, then heated to 700 ℃ at a heating rate of 7.5 ℃ / min, while the pressure was increased to 30 MPa at a rate of 1 MPa / min and kept at this temperature and pressure for 120 min, then slowly cooled in the furnace, when the temperature dropped to 400 ℃, the pressure was reduced at a rate of 0.2 MPa / min, and finally a vacuum hot-pressed Cu-15Sn-0.3Ti alloy test bar was obtained. The average grain size of the vacuum hot-pressed Cu-15Sn-0.3Ti alloy test bar obtained was 17.89 μm, the density was 88.24%, the conductivity was 3.84 MS / m, the hardness was 75.50 HB, and the elongation at break was 36.00%.

[0051] Example 2

[0052] The preparation method of fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy is specifically as follows:

[0053] Weigh 84.7% Cu powder, 15% Sn powder, and 0.3% Ti powder, and mix them in a ball mill mixer. Control the ball mill speed to 120r / min, the forward and reverse rotation time to 10min, and the mixing time to 12h.

[0054] Weigh 2680g of the uniformly mixed Cu powder, Sn powder, and Ti powder, and evenly fill them into the rubber bag for sealing and vacuum degassing. Place the bag in a cold isostatic press, control the pressing force to 190MPa, the pressure increase rate to 18MPa / min, the holding time to 5min, and take out the cold pressed billet after unloading.

[0055] The Cu-15Sn-0.3Ti alloy cold pressed billet was placed in a vacuum hot pressing sintering furnace and the vacuum degree in the furnace was reduced to 6.8×10 -3 Pa, first, the temperature was increased from room temperature to 550°C at a heating rate of 15.5°C / min, and the pressure was increased to 20MPa at a heating rate of 2MPa / min, and then kept at this temperature and pressure for 20min. Secondly, the temperature was increased to 700°C at a heating rate of 7.5°C / min, and the pressure was increased to 30MPa at a heating rate of 1MPa / min, and then kept at this temperature and pressure for 120min. After that, the temperature was slowly cooled with the furnace. When the temperature was reduced to 400°C, the pressure was reduced at a rate of 0.2MPa / min, and finally a vacuum hot-pressed Cu-15Sn-0.3Ti alloy test bar was obtained.

[0056] A copper sheath with a diameter of 68 mm, an internal aperture of 62 mm, and a length of 100 mm was machined. A vacuum hot-pressed Cu-15Sn-0.3Ti alloy rod was placed within the sheath. A copper cap with a thickness of 10 mm was then placed and vacuum diffusion welded to the sheath, tightly encasing the rod. The rod was then softened in a nitrogen furnace at 600°C for 120 minutes. After this, the rod was immediately placed in an extrusion barrel preheated to 400°C for hot extrusion. The extrusion force was maintained at no less than 4500 kN, the extrusion rate was 15 mm / s, and the extrusion ratio was 12:1. This resulted in a hot-extruded Cu-15Sn-0.3Ti alloy rod with a diameter of 18 mm.

[0057] The hot-extruded Cu-15Sn-0.3Ti alloy rods were solution treated in a box-type resistance furnace at 550°C for 80 hours and then water quenched to produce a fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy. The resulting Cu-15Sn-0.3Ti alloy exhibited an average grain size of 9.89 μm, a density of 99.73%, a conductivity of 4.09 MS / m, a hardness of 91.8 HB, and an elongation of 43.51%.

[0058] Example 3

[0059] The preparation method of fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy is specifically as follows:

[0060] Weigh 84.7% Cu powder, 15% Sn powder, and 0.3% Ti powder, and mix them in a ball mill mixer. Control the ball mill speed to 140r / min, the forward and reverse rotation time to 15min, and the mixing time to 18h.

[0061] Weigh 2685g of the uniformly mixed Cu powder, Sn powder, and Ti powder, and evenly fill them into the rubber bag for sealing and vacuum degassing. Place the bag in a cold isostatic press, control the pressing force to 170MPa, the pressure increase rate to 10MPa / min, the holding time to 15min, and take out the cold pressed billet after unloading.

[0062] The Cu-15Sn-0.3Ti alloy cold pressed billet was placed in a vacuum hot pressing sintering furnace and the vacuum degree in the furnace was reduced to 6.8×10 -3Pa, first, the temperature was increased from room temperature to 550°C at a heating rate of 15.5°C / min, and the pressure was increased to 20MPa at a heating rate of 2MPa / min, and then kept at this temperature and pressure for 20min. Secondly, the temperature was increased to 710°C at a heating rate of 7.5°C / min, and the pressure was increased to 30MPa at a heating rate of 1MPa / min, and then kept at this temperature and pressure for 120min. After that, the furnace was slowly cooled. When the temperature was reduced to 400°C, the pressure was reduced at a rate of 0.2MPa / min, and finally a vacuum hot-pressed Cu-15Sn-0.3Ti alloy test bar was obtained.

[0063] A copper sheath with a diameter of 68 mm, an internal aperture of 62 mm, and a length of 100 mm was machined. A vacuum hot-pressed Cu-15Sn-0.3Ti alloy rod was placed within the sheath. A copper cap with a thickness of 10 mm was then fitted to the sheath and vacuum diffusion welded to tightly encase the rod. The rod was then softened in a nitrogen furnace at 616°C for 123 minutes. Afterwards, the rod was immediately placed in an extrusion barrel preheated to 400°C for hot extrusion. The extrusion force was maintained at no less than 4500 kN, the extrusion rate was 10 mm / s, and the extrusion ratio was 12:1. The resulting hot-extruded Cu-15Sn-0.3Ti alloy rod had a diameter of 18 mm.

[0064] The hot-extruded Cu-15Sn-0.3Ti alloy rods were solution treated in a box-type resistance furnace at 580°C for 80 hours and then water quenched to produce a fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy. The resulting Cu-15Sn-0.3Ti alloy exhibited an average grain size of 9.37 μm, a density of 98.70%, a conductivity of 4.24 MS / m, a hardness of 86.8 HB, and an elongation of 47.13%.

[0065] Example 4

[0066] The preparation method of fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy is specifically as follows:

[0067] Weigh 84.7% Cu powder, 15% Sn powder, and 0.3% Ti powder, and mix them in a ball mill mixer. Control the ball mill speed to 160r / min, the forward and reverse rotation time to 15min, and the mixing time to 20h.

[0068] Weigh 2680g of the uniformly mixed Cu powder, Sn powder, and Ti powder, and evenly fill them into the rubber bag for sealing and vacuum degassing. Place the bag in a cold isostatic press, control the pressing force to 175MPa, the pressure increase rate to 13MPa / min, the holding time to 13min, and take out the cold pressed billet after unloading.

[0069] The Cu-15Sn-0.3Ti alloy cold pressed billet was placed in a vacuum hot pressing sintering furnace and the vacuum degree in the furnace was reduced to 6.8×10 -3 Pa, first, the temperature was increased from room temperature to 550°C at a heating rate of 15.5°C / min, and the pressure was increased to 20MPa at a heating rate of 2MPa / min, and then kept at this temperature and pressure for 20min. Secondly, the temperature was increased to 705°C at a heating rate of 7.5°C / min, and the pressure was increased to 30MPa at a heating rate of 1MPa / min, and then kept at this temperature and pressure for 120min. After that, the furnace was slowly cooled. When the temperature was reduced to 400°C, the pressure was reduced at a rate of 0.2MPa / min, and finally a vacuum hot-pressed Cu-15Sn-0.3Ti alloy test bar was obtained.

[0070] A copper sheath with a diameter of 68 mm, an internal aperture of 62 mm, and a length of 100 mm was machined. A vacuum hot-pressed Cu-15Sn-0.3Ti alloy rod was placed within the sheath. A copper cap with a thickness of 10 mm was then fitted to the sheath and vacuum diffusion welded to tightly encase the rod. The rod was then softened in a nitrogen furnace at 632°C for 118 minutes. After this, the rod was immediately placed in an extrusion barrel preheated to 400°C for hot extrusion. The extrusion force was maintained at no less than 4500 kN, the extrusion rate was 20 mm / s, and the extrusion ratio was 12:1. This resulted in a hot-extruded Cu-15Sn-0.3Ti alloy rod with a diameter of 18 mm.

[0071] The hot-extruded Cu-15Sn-0.3Ti alloy rods were solution treated in a box-type resistance furnace at 575°C for 80 hours and then water quenched to produce a fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy. The resulting Cu-15Sn-0.3Ti alloy exhibited an average grain size of 8.21 μm, a density of 98.00%, a conductivity of 3.98 MS / m, a hardness of 80.4 HB, and an elongation of 51.07%.

[0072] Example 5

[0073] The preparation method of fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy is specifically as follows:

[0074] Weigh 84.7% Cu powder, 15% Sn powder, and 0.3% Ti powder, and mix them in a ball mill mixer. Control the ball mill speed to 180r / min, the forward and reverse rotation time to 18min, and the mixing time to 24h.

[0075] Weigh 2680g of the uniformly mixed Cu powder, Sn powder, and Ti powder, and evenly fill them into the rubber bag for sealing and vacuum degassing. Place the bag in a cold isostatic press, control the pressing force to 185MPa, the pressure increase rate to 17MPa / min, the holding time to 8min, and take out the cold pressed billet after unloading.

[0076] The Cu-15Sn-0.3Ti alloy cold pressed billet was placed in a vacuum hot pressing sintering furnace and the vacuum degree in the furnace was reduced to 6.8×10 -3 Pa, first, the temperature was increased from room temperature to 550°C at a heating rate of 15.5°C / min, and the pressure was increased to 20MPa at a heating rate of 2MPa / min, and then kept at this temperature and pressure for 20min. Secondly, the temperature was increased to 725°C at a heating rate of 7.5°C / min, and the pressure was increased to 30MPa at a heating rate of 1MPa / min, and then kept at this temperature and pressure for 120min. After that, the furnace was slowly cooled. When the temperature was reduced to 400°C, the pressure was reduced at a rate of 0.2MPa / min, and finally a vacuum hot-pressed Cu-15Sn-0.3Ti alloy test bar was obtained.

[0077] A copper sheath with a diameter of 68 mm, an internal aperture of 62 mm, and a length of 100 mm was machined. A vacuum hot-pressed Cu-15Sn-0.3Ti alloy rod was placed within the sheath. A copper cap with a thickness of 10 mm was then fitted to the sheath and vacuum diffusion welded to tightly encase the rod. The rod was then softened in a nitrogen furnace at 650°C for 125 minutes. Afterwards, the rod was immediately placed in an extrusion barrel preheated to 400°C for hot extrusion. The extrusion force was maintained at no less than 4500 kN, the extrusion rate was 18 mm / s, and the extrusion ratio was 12:1. This resulted in a hot-extruded Cu-15Sn-0.3Ti alloy rod with a diameter of 18 mm.

[0078] The hot-extruded Cu-15Sn-0.3Ti alloy rods were solution treated in a box-type resistance furnace at 600°C for 80 hours and then water quenched to produce a fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy. The resulting Cu-15Sn-0.3Ti alloy exhibited an average grain size of 7.38 μm, a density of 99.14%, a conductivity of 4.21 MS / m, a hardness of 91.8 HB, and an elongation of 53.67%.

[0079] Figure 1 This is a microstructure photograph of the fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy in Example 5. It can be seen that the alloy structure has fine equiaxed grains and high-density twins.

[0080] Figure 2 1 is the stress-strain curve of the Cu-15Sn-0.3Ti alloy in Examples 1-5. It can be seen that with the increase of hot extrusion pressure and speed, the strength of the Cu-15Sn-0.3Ti alloy gradually decreases and the plasticity gradually increases.

[0081] Figure 3 This is the density curve of the Cu-15Sn-0.3Ti alloy in Example 1-5. It can be seen that the density of the vacuum hot pressing sintering + hot extrusion Cu-15Sn-0.3Ti alloy is greatly improved compared with the vacuum hot pressing sintering Cu-15Sn-0.3Ti alloy. With the increase of hot extrusion pressure and speed, the density of the alloy is above 98%.

[0082] Figure 4 3. The hardness and conductivity curves of the Cu-15Sn-0.3Ti alloy in Examples 1-5 show that the hardness and conductivity of the vacuum hot pressing sintering + hot extrusion Cu-15Sn-0.3Ti alloy are higher than those of the vacuum hot pressing sintering Cu-15Sn-0.3Ti alloy. With the increase of hot extrusion pressure and speed, the hardness of the alloy is not less than 80.4HB, and the conductivity is above 3.98MS / m.

[0083] Figure 5 This is a graph of the average grain size of the Cu-15Sn-0.3Ti alloy in Examples 1-5. It can be seen that with the change of the vacuum hot pressing sintering + hot extrusion composite process, the grain size of the Cu-15Sn-0.3Ti alloy gradually decreases. The fine grain size provides higher strength and higher elongation. The minimum average grain size of the alloy is 7.38μm.

Claims

1. A method for preparing a fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy, characterized in that: Please follow the steps below to implement: Step 1: ball-mill Cu powder, Sn powder and Ti powder in proportion to obtain mixed powder; Step 2: The mixed powder is evenly filled into a rubber sleeve for sealing and vacuum degassing, and the sleeve is placed in a cold isostatic press for cold isostatic pressing to obtain a Cu-15Sn-0.3Ti alloy cold pressed billet; Step 3: placing the Cu-15Sn-0.3Ti alloy cold pressed blank into a vacuum hot pressing sintering furnace for vacuum hot pressing sintering to obtain a Cu-15Sn-0.3Ti alloy test bar; During vacuum hot pressing sintering: the vacuum degree in the furnace is reduced to 6.8×10 -3 Pa, firstly, the temperature was increased from room temperature to 550°C at a heating rate of 15.5°C / min, and at the same time, the pressure was increased to 20MPa at a heating rate of 2MPa / min, and then kept at this temperature and pressure for 20min. Secondly, the temperature was increased to 700-725°C at a heating rate of 7.5°C / min, and at the same time, the pressure was increased to 30MPa at a heating rate of 1MPa / min, and kept at this temperature and pressure for 120min. Then, the temperature was slowly cooled with the furnace. When the temperature dropped to 400°C, the pressure was reduced at a rate of 0.2MPa / min, and finally a Cu-15Sn-0.3Ti alloy test bar after vacuum hot pressing sintering was obtained. Step 4: hot extruding the Cu-15Sn-0.3Ti alloy test bar to obtain a hot-extruded Cu-15Sn-0.3Ti alloy bar; During hot extrusion treatment: control the extrusion pressure to no less than 4500KN, the extrusion rate to 10~20mm / s, and the extrusion ratio to 12:1; Step 5: The hot-extruded Cu-15Sn-0.3Ti alloy rod is solution treated and water quenched to obtain a fine-grained, high-plasticity, and high-density Cu-15Sn-0.3Ti alloy.

2. The method for preparing the fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy according to claim 1, characterized in that: In the step 1, by mass percentage, 84.7% Cu powder, 15% Sn powder, and 0.3% Ti powder are prepared, and the sum of the components is 100%.

3. The method for preparing the fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy according to claim 1, characterized in that: In step 1, during ball milling, the ball mill speed is controlled to be 120-180 r / min, the forward and reverse rotation time is 10-18 min, and the powder mixing time is 12-24 h.

4. The method for preparing the fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy according to claim 1, characterized in that: In step 2, during the cold isostatic pressing treatment, the pressing force is controlled to be 180±10 MPa, the pressure increasing rate is 10-18 MPa / min, and the holding time is 10±5 min.

5. The method for preparing the fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy according to claim 1, characterized in that: In the step 4, specifically: The Cu-15Sn-0.3Ti alloy rod after vacuum hot pressing sintering was placed in a copper sleeve, and a copper cover was matched with the copper sleeve and vacuum diffusion welding was performed to make the Cu-15Sn-0.3Ti alloy test rod tightly wrapped by the copper sleeve as a whole. The whole was placed in a nitrogen heating furnace with a holding temperature of 600-650°C for softening treatment for 120±5min. After the holding period, it was immediately placed in an extrusion barrel preheated to 400°C for hot extrusion treatment to obtain the hot-extruded Cu-15Sn-0.3Ti alloy rod.

6. The method for preparing the fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy according to claim 1, characterized in that: In step 5, the solution treatment temperature is 550-600° C., and the solution treatment time is 80 h.

7. Fine-grained, high-plasticity, high-density Cu-15Sn-0.3Ti alloy, characterized by: The method is prepared by any one of claims 1 to 6.

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