Planetary low‐temperature high‐energy ball mill was used for preparing the mixed powders with different particle sizes by adjusting the milling time. The ultrafine grain gradient cemented carbides were prepared by sinter‐HIP treatment. The effects of milling time on the gradient formation, grain growth, and mechanical properties of ultrafine grain gradient cemented carbides were investigated. The results show that the high‐energy ball milling cannot effectively reduce the particle size of mixed powder with short milling time. In addition, the particle size of the mixed powder is significantly reduced, while the specific surface area is significantly increased when the ball milling time exceeds 25 hours. The gradient layer thickness and the grain size increase at the beginning and then decrease when the mixed powder particle size was decreased. Simultaneously, the density, hardness, and fracture toughness of the alloy increase gradually. On the contrary, the number of WC with abnormal grain growth is significantly increased. The thickness of the gradient layer reached 32 μm, and the mean WC grain size is 314 nm. Based on the analyzed results, an optimized gradient layer thickness, grain size, density, and hardness can be obtained when the ball milling time is 35 hours.

中文翻译：

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高能球磨对超细梯度硬质合金组织和性能的影响

行星式低温高能球磨机通过调节研磨时间来制备具有不同粒径的混合粉末。通过烧结HIP处理制备了超细晶粒梯度硬质合金。研究了铣削时间对超细晶粒梯度硬质合金的梯度形成，晶粒长大和力学性能的影响。结果表明，高能球磨不能在短时间内降低混合粉末的粒径。另外，当球磨时间超过25小时时，混合粉末的粒径显着减小，而比表面积显着增大。梯度层厚度和晶粒尺寸在开始时增加，然后在减小混合粉末的粒径时减小。同时，合金的密度，硬度和断裂韧性逐渐增加。相反，具有异常晶粒生长的WC的数量显着增加。梯度层的厚度达到32μm，并且WC的平均粒径为314nm。根据分析结果，当球磨时间为35小时时，可以获得最佳的梯度层厚度，晶粒尺寸，密度和硬度。