Monel-400 alloy is a nickel based alloy, mainly composed of nickel metal and also containing copper metal. It has excellent physical properties such as high strength and high corrosion resistance, while also exhibiting good physical and mechanical properties. Therefore, Monel-400 alloy is widely used in key components in advanced industrial fields such as petrochemical, nuclear, and defense industries. However, due to the small thermal conductivity (21.744W/mK) and linear expansion coefficient (13.86) of monel-400 alloy × 10 ⁻ * K ', therefore it is susceptible to the influence of hot cracking tendency during the welding process. Under local heating and cooling conditions, serious stress and deformation problems may occur, leading to the occurrence of weld solidification cracks in welded joints. Currently, research on the mechanical properties of monel-400 alloy at high temperatures is very limited.
test method
The high-temperature tensile test of Monel-400 alloy was carried out on the Gleeble-1500D thermal simulation testing machine. According to the test requirements, the material needs to be processed by molybdenum wire cutting to produce the following specifications: φ six × A 120mm specimen. Before conducting the experiment, it is necessary to ensure that the surface treatment of the specimen is clean and to measure its original diameter. After installing the sample onto the thermal simulator, measure the gauge size between the two clamps. The heating of the sample is achieved by placing the sample into a closed loop of the simulator. Heat the sample at a rate of 10 degrees Celsius per second to 1100 degrees Celsius and hold for 3 minutes, then lower it at a rate of 3 degrees Celsius per second to different test temperatures (600 degrees Celsius, 700 degrees Celsius, 800 degrees Celsius, 900 degrees Celsius, 1000 degrees Celsius, and 1100 degrees Celsius, respectively). At each test temperature, start stretching at a strain rate of 10 negative cubic times per second until the sample fractures. The entire experimental process was completed in a vacuum state. Finally, the fracture surface of the high-temperature tensile specimen was manually sawn off and made into a scanning electron microscope sample. The scanning of the fracture surface was completed under the scanning electron microscope.
Results
High temperature tensile performance
The stress-strain curves under tension at different temperatures can be seen in Monel-400 alloy in Figure 2. According to the graph, as the test temperature increases, the strength of Monel-400 alloy significantly weakens and the tensile strength also decreases. For example, the tensile strength of the alloy is 106.49 MPa at a temperature of 600 ℃ and 22.41 MPa at 1100 ℃, indicating that the deformation temperature has a significant impact on the deformation resistance of the alloy. The elastic deformation of the alloy is relatively small, but with the increase of temperature, the plastic deformation increases significantly. The increase from 11.22% to 20.05% at 900 ℃ and the increase in cross-sectional shrinkage from 20.47% at 700 ℃ to 60.05% at 900 ℃ indicate that plasticity becomes better and better with the increase of tensile temperature within this temperature range. As the stretching temperature continues to increase, the plasticity of the alloy shows a decreasing trend, and it basically decreases to the level at 800 ℃ when it reaches 1100 ℃. From the overall curve, it shows a trend of first increasing and then decreasing, indicating that the high-temperature plasticity of Monel-400 alloy first improves with the increase of tensile temperature and reaches a good performance at around 900 ℃. Then, with the increase of tensile temperature, the high-temperature plasticity deteriorates until it approaches the low-temperature level