Method for promoting phase change strengthening and toughening of two-phase titanium alloy strip by using pulse current and strip

Abstract

The invention discloses a method for promoting phase change strengthening and toughening of a two-phase titanium alloy strip by using pulse current. The method comprises the following steps: tensioning a TC4 titanium alloy strip through a decoiling device, a winding device, a roller and a support roller of a rolling mill, so that the strip is in tightly elastic contact with the roller; driving the strip to transmit at the speed of 150-800mm / min through friction force by virtue of the roller; inputting the pulse current into a power-up area section of the strip through the roller, the support roller and the like, wherein the pulse current generates a joule heating effect and a non-thermal effect in the power-up area section of the strip within 12-18 seconds, so that the internal microstructure of the strip turns into a two-phase long-axis structure or a two-phase dual-state structure from an original quasi-single phase thick equiaxed structure; and then cooling by natural air at room temperature. Through adjustment of parameters of the pulse current, the TC4 strip with the two-phase long-axis structure and the two-phase dual-state structure can be quickly obtained, thus the ductility is increased; the treatment temperature is far lower than 960 DEG C of a traditional thermal treatment process; the processing process of the titanium alloy strip can be finished without a short period of time at relatively low temperature without an oxidation phenomenon; and therefore, the method is energy-saving, environmentally friendly, safe and efficient.

Description

technical field [0001] The present invention relates to pulse current phase transformation strengthening and toughening online processing technology for two-phase titanium alloy strips, in particular to a pulse current online processing technology for two-phase TC4 titanium alloy strips with good comprehensive mechanical properties, and through pulse current phase TC4 two-phase titanium alloy strips with good comprehensive mechanical properties can be obtained by the on-line treatment process of strengthening and toughening. Background technique [0002] With the global energy crisis and environmental pollution becoming more and more serious, in order to reduce energy consumption and reduce environmental pollution caused by motor machinery exhaust emissions, in the fields of aviation, aerospace and automobiles, the benefits of lightweight structures are very significant, including The mobility of the aircraft and the motor vehicle can be improved, the fuel consumption can be...

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Problems solved by technology

The traditional complete annealing heat treatment process can improve the plasticity of TC4 titanium alloy to a certain extent, but its strength will be seriously reduced due to the precipitation of a large amount of β-Ti from the titanium matrix.

In addition, due to the slow diffusion rate of solute atoms in the solid phase in titanium alloys, the complete annealing process of general titanium alloys has high heating temperature (above 960°C) and long holding time (depending on the batch size in the furnace, generally a few hours) and high energy consumption. Due to high heating temperature and long holding time, the surface of titanium alloy is easy to oxidize, especially once local surface oxidation occurs on titanium alloy plates and strips, it is difficult to remove the oxide layer in subsequent treatment, which is serious. It affects the subsequent molding process and the quality of the final product; at the same time, under the condition of long-term high temperature, the TC4 titanium alloy is prone to abnormal grain growth, which directly leads to serious uneven grain size inside the material and seriously damages the final mechanical properties of the material

Furthermore, the heating method and heating speed of the titanium alloy must be strictly controlled to prevent that once the heating method and heating speed are selected improperly, the internal temperature of the material will be uneven and local overburning will eventually lead to the internal temperature of the material after solution treatment. The consequences of uneven structure and unstable mechanical properties, so the factors affecting the traditional heat treatment process are complicated and the production cost is high

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