With the rapid development and the improvement of the accuracy requirements in many science fields, micromechanical systems (MEMS) have developed rapidly, and the demand for miniaturization of materials is also increasing year by year [
1,
2,
3]. Because of the excellent electrical conductivity and ductility of copper and its alloys, they are widely used in micro-parts of precision instruments [
4,
5,
6]. Unfortunately, when the sheet thickness reaches the accuracy of millimeters and below, the mechanical properties often show a size effect which differs from that of conventional materials, and the phenomenon becomes more obvious with decreasing sheet thickness [
7,
8]. Moreover, as the sheet thickness decreases, the influence of the service temperature on the performance of the material might become more pronounced and cannot be ignored.
In recent years, many workers have identified the phenomenon that, when the thickness is small, the mechanical properties of copper and its alloys are contrary to those of conventional materials. It was found that, when the sheet thickness is above the millimeter scale, the relevant mechanical properties of sheets of materials such as aluminum and steel deteriorate as the thickness of the sample decreases [
9,
10,
11]. When the sheet size is on the micrometer scale, researchers found that different materials exhibit different mechanical properties compared to conventional materials. Wu et al. [
12] studied the mechanical behavior of 304 stainless steel and found that the yield strength first increased and then decreased, while the tensile strength and elongation showed opposite properties; the finite element model of rigid die bulging was established. Wan et al. [
13] applied a self-developed micro asymmetric mill to produce a CP–copper ultrathin strip, revealing that the tensile strength and hardness first increased and then decreased with the decrease of thickness. Zhang et al. [
14] carried out tensile test on a 0.1–1.0 mm copper sheet. The test results showed that the tensile strength, the maximum uniform strain, and the fracture strain decreased with the decrease in sheet thickness, while the yield strength exhibited the opposite trend. Lee [
15] and Yu et al. [
16] found that the yield strength increased with the decrease in thickness in the tensile test of 0.1–10 µm metal film. Li et al. [
17,
18] carried out microscale bending experiments on pure aluminum foil and pure copper with different thicknesses. The experimental results showed that the spring-back angle increased with the decrease in thickness, while the flow stress increased with the decrease in foil thickness. A change in temperature also has a huge impact on the mechanical properties of the material. He et al. [
19] tested the effect of heat treatment on 304 stainless steel. The test results indicated that the strength and elongation were decreased after heat treatment. Meng et al. [
20] heat-treated pure copper of different thicknesses and found that the mechanical properties of thinner samples of pure copper decreased with heat treatment, while the opposite was seen for thicker samples of pure copper. Kori et al. [
21] conducted room-temperature and high-temperature (100 °C, 200 °C, 300 °C) tensile tests on 304 stainless steel samples and found that the yield strength and elongation decreased initially and then increased within the test range, while the tensile strength value decreased. Zhang et al. [
22] performed room- and cryogenic-temperature tensile tests on pure copper samples after heat treatment, finding that the strength and ductility obtained at −196 °C were higher than for tensile samples deformed at 22 °C. At present, there have been many achievements in the research on the influence of thickness and heat treatment on the mechanical properties of thin sheets, and the influence of service temperature on material properties has gradually been elucidated. However, the related research on the joint effect of sheet thickness and service temperature on the mechanical properties of sheets is still rare.
In the present study, a thin T2 copper sheet was employed to investigate the effect of thickness and service temperature on its tensile properties. To investigate the change law of tensile properties referring to tensile strength, yield strength, and elongation, uniaxial static tensile tests were performed on T2 copper sheets of various thicknesses from 0.08 mm to 1.0 mm at different test temperatures. Moreover, variables of sheet thickness and test temperature were defined so as to establish their relationships with tensile properties.