Upon deforming a metallic glass at low temperatures, shear tends to localize and this leads to a brittle behavior. However, in the high temperature, and particularly in the supercooled liquid region, homogeneous defor...Upon deforming a metallic glass at low temperatures, shear tends to localize and this leads to a brittle behavior. However, in the high temperature, and particularly in the supercooled liquid region, homogeneous deformation begins to take place. A bulk amorphous Zr 10Al 5Ti 17.9Cu 14.6Ni alloy was observed to exhibit the Newtonian behavior at low strain rates but becomes non Newtonian at high strain rates in the supercooled liquid region. Structures of the amorphous material, both before and after deformation, were examined using X ray diffraction and high resolution electron microscopy. Results showed the presence of nanocrystallites in the deformed samples. Thus, the non Newtonian behavior is attributable to the concurrent crystallization of the amorphous structure during deformation. A mechanistic model is presented to interpret the observed non Newtonian result. A phenomenological approach is also used to develop the deformation map for bulk metallic glasses in the supercooled liquid region.展开更多
New Fe-based multicomponent amorphous alloys have been developed recently based on empirical rules for large glass forming ability(GFA). In the present investigation, the master alloy ingot with the nominal compositio...New Fe-based multicomponent amorphous alloys have been developed recently based on empirical rules for large glass forming ability(GFA). In the present investigation, the master alloy ingot with the nominal composition of Fe 61Co 7Zr 10Mo 5W 2B 15(mole fraction, %) was prepared by arc-melting under Ti-gettered Ar atmosphere. The Fe-based buttons with different transverse cross sections were fabricated by arc-melting method, and the d 2.5 mm Fe-based rods were manufactured by injection technique. Characterization of the ingots and the parameters associated with the thermal stability were carried out by X-ray diffractometry(XRD) and high temperature differential scanning calorimeter(DSC), respectively. The interval of the supercooled liquid region is 39 K for the Fe-based alloy. The GFA of Fe-based alloys is relatively lower, to the buttons obtained are all crystallized. The Fe-based rod exhibites a high Vickers hardness up to HV 1 329. In addition, an amorphous-crystalline transition layers are observed in the rod. This transition zone is caused by unhomogeneous temperature distribution and relatively lower GFA for Fe-based alloys.展开更多
通过对材料动态力学性能的测试,研究了采用快速凝固/粉末冶金工艺制备的Al Fe Mo Si基复合阻尼材料Al Fe Mo Si/Zn Al和Al Fe Mo Si/Al/Zn Al的阻尼性能,并对其阻尼机制进行了讨论。结果表明:在20～250℃的温度范围内,两种材料的阻尼性...通过对材料动态力学性能的测试,研究了采用快速凝固/粉末冶金工艺制备的Al Fe Mo Si基复合阻尼材料Al Fe Mo Si/Zn Al和Al Fe Mo Si/Al/Zn Al的阻尼性能,并对其阻尼机制进行了讨论。结果表明:在20～250℃的温度范围内,两种材料的阻尼性能(Q-1)处于(0 5～3 1)×10-2之间,复合有较多Zn Al且挤压比较大的Al Fe Mo Si/Zn Al的阻尼性能要优于Al Fe Mo Si/Al/Zn Al。低温时由大挤压变形引入的高密度位错阻尼在材料内耗机制中占据主导地位,而在高温区界面阻尼的影响逐渐增加,同时由于热激活作用,位错阻尼随着温度的升高表现出不同的作用机制,二者共同决定着材料的内耗特性。展开更多
文摘Upon deforming a metallic glass at low temperatures, shear tends to localize and this leads to a brittle behavior. However, in the high temperature, and particularly in the supercooled liquid region, homogeneous deformation begins to take place. A bulk amorphous Zr 10Al 5Ti 17.9Cu 14.6Ni alloy was observed to exhibit the Newtonian behavior at low strain rates but becomes non Newtonian at high strain rates in the supercooled liquid region. Structures of the amorphous material, both before and after deformation, were examined using X ray diffraction and high resolution electron microscopy. Results showed the presence of nanocrystallites in the deformed samples. Thus, the non Newtonian behavior is attributable to the concurrent crystallization of the amorphous structure during deformation. A mechanistic model is presented to interpret the observed non Newtonian result. A phenomenological approach is also used to develop the deformation map for bulk metallic glasses in the supercooled liquid region.
文摘New Fe-based multicomponent amorphous alloys have been developed recently based on empirical rules for large glass forming ability(GFA). In the present investigation, the master alloy ingot with the nominal composition of Fe 61Co 7Zr 10Mo 5W 2B 15(mole fraction, %) was prepared by arc-melting under Ti-gettered Ar atmosphere. The Fe-based buttons with different transverse cross sections were fabricated by arc-melting method, and the d 2.5 mm Fe-based rods were manufactured by injection technique. Characterization of the ingots and the parameters associated with the thermal stability were carried out by X-ray diffractometry(XRD) and high temperature differential scanning calorimeter(DSC), respectively. The interval of the supercooled liquid region is 39 K for the Fe-based alloy. The GFA of Fe-based alloys is relatively lower, to the buttons obtained are all crystallized. The Fe-based rod exhibites a high Vickers hardness up to HV 1 329. In addition, an amorphous-crystalline transition layers are observed in the rod. This transition zone is caused by unhomogeneous temperature distribution and relatively lower GFA for Fe-based alloys.
文摘通过对材料动态力学性能的测试,研究了采用快速凝固/粉末冶金工艺制备的Al Fe Mo Si基复合阻尼材料Al Fe Mo Si/Zn Al和Al Fe Mo Si/Al/Zn Al的阻尼性能,并对其阻尼机制进行了讨论。结果表明:在20～250℃的温度范围内,两种材料的阻尼性能(Q-1)处于(0 5～3 1)×10-2之间,复合有较多Zn Al且挤压比较大的Al Fe Mo Si/Zn Al的阻尼性能要优于Al Fe Mo Si/Al/Zn Al。低温时由大挤压变形引入的高密度位错阻尼在材料内耗机制中占据主导地位,而在高温区界面阻尼的影响逐渐增加,同时由于热激活作用,位错阻尼随着温度的升高表现出不同的作用机制,二者共同决定着材料的内耗特性。
