The average grain degrees less than 0.5 μm of fine-grained W-40Cu and W-50Cu alloys are studied by tensile testing in the temperature range of 200～800 ℃. The research on its fracture mechanism and micro-structural change rules at high temperature is conducted by SEM micrograph observation. The results show that the ultimate tensile strength (UTS) of the alloys decreases sharply with the increase of temperature. The elongation of W-40Cu and W-50Cu alloys decrease slightly below 400 ℃. However, the elongation of W-40Cu and W-50Cu alloys increase sharply with the increase of temperature when the temperature is above 400 ℃. Fracture characteristics show Fine-grain W-Cu alloy fracture mainly includes W particles' inter-granular rupture and Cu phase's ductility tears in room temperature. W-Cu alloy's elongation shows change due to copper alloys "medium temperature brittle"influence at the temperature of 400 ℃. When the temperature rises to 800 ℃, W-Cu alloys shows ductile fracture characteristics mainly by the fracture mode Cu phase influence.%研究了平均晶粒度在0.5μm以下细晶W-40Cu和W-50Cu合金在200～800℃范围内的高温拉伸力学行为,并结合SEM断口形貌分析了材料在高温状态下的断裂形式及其组织变化规律.结果表明:W-Cu合金拉伸强度随温度升高而迅速降低,其延伸率在室温至400℃温度区间时变化不大;当温度大于400℃时,合金延伸率迅速上升.拉伸断口特征表明:在室温条件下,细晶W-Cu合金的断裂主要包括W晶粒的沿晶断裂与Cu相的延性撕裂:温度在400℃时,Cu相开始软化,但合金材料受铜的"中温脆性"影响而使得材料的断裂延伸率变化不大;当温度达到800℃时,材料的断裂方式主要受Cu相的影响而表现出很好的延性断裂.
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