激光粉末床熔融(laser powder bed fusion,LPBF)成形NiTi合金由于Ni元素的蒸发导致成分偏离粉末设计成分,而NiTi合金的形状记忆效应、超弹性等性能受Ni含量影响极大。因此有必要对不同Ni含量NiTi合金的LPBF成形性、显微组织以及力学性...激光粉末床熔融(laser powder bed fusion,LPBF)成形NiTi合金由于Ni元素的蒸发导致成分偏离粉末设计成分,而NiTi合金的形状记忆效应、超弹性等性能受Ni含量影响极大。因此有必要对不同Ni含量NiTi合金的LPBF成形性、显微组织以及力学性能开展研究。采用真空电极感应熔炼气雾化技术制备了Ni_(50.8)Ti、Ni_(51.0)Ti以及Ni_(51.5)Ti(原子分数,%)3种预合金粉末,研究其在不同工艺参数下的冶金缺陷、显微组织及力学性能的演化规律。结果表明,高Ni含量NiTi合金在LPBF成形过程中容易产生垂直于建造方向的裂纹,成形性较低Ni含量NiTi合金差。Ni_(51.5)Ti合金室温下的临界应力可达476 MPa,但断裂伸长率仅为2%;Ni_(50.8)Ti合金临界应力仅为122 MPa,断裂伸长率可达8%。展开更多
Creep deformation can be classified as homogeneous flow and inhomogeneous flow in bulk metallic glass(BMG).In order to understand the conversion conditions of the two types of creep deformation,the effect of loading r...Creep deformation can be classified as homogeneous flow and inhomogeneous flow in bulk metallic glass(BMG).In order to understand the conversion conditions of the two types of creep deformation,the effect of loading rate on the creep behavior of a Ti_(40)Zr_(10)Cu_(47)Sn_(3)(at.%)BMG at ambient temperature was investigated using nanoindentation and molecular dynamic simulation.Results indicate that at low loading rates,many serrations appear in loading stage,leading to inhomogeneous serrated flow in the creep stage.When the loading rate is high enough,the creep deformation tends to be homogeneous.The related mechanism responsible for the rate-dependent creep behavior is attributed to the number of pre-existing major shear bands which is influenced significantly by the loading rate.展开更多
基金supported by the National Key Research and Development Program of China(No.2016YFB1100103)the National Natural Science Foundation of China(No.51771233)+2 种基金Key Research and Development Program of Hunan Province,China(No.2016JC2003)China Postdoctoral Science Foundation(No.2018M633164)Fundamental Research Funds for the Central Universities of Central South University,China(Nos.2018ZZTS127,CX20190190,2019ZZTS134)。
文摘Creep deformation can be classified as homogeneous flow and inhomogeneous flow in bulk metallic glass(BMG).In order to understand the conversion conditions of the two types of creep deformation,the effect of loading rate on the creep behavior of a Ti_(40)Zr_(10)Cu_(47)Sn_(3)(at.%)BMG at ambient temperature was investigated using nanoindentation and molecular dynamic simulation.Results indicate that at low loading rates,many serrations appear in loading stage,leading to inhomogeneous serrated flow in the creep stage.When the loading rate is high enough,the creep deformation tends to be homogeneous.The related mechanism responsible for the rate-dependent creep behavior is attributed to the number of pre-existing major shear bands which is influenced significantly by the loading rate.
