Deformation temperature and postdeformation annealing effects on severely deformed TiNi alloy by equal channel angular extrusion

Micron TiNi alloy blocks were fabricated at high temperature by equal channel angular extrusion （ECAE） using hotforged Ti-50.3at%Ni alloy as the raw material and the effects of deformation temperature and postdeformation annealing on the severely deformed TiNi alloy by ECAE were investigated. The results show that the TiNi alloy processed by ECAE undergoes severe plastic deformation, and lowering the deformation temperature and increasing the number of extrusions contribute to grain refinement. When the annealing temperature is below 873 K, static recovery is the main restoration process; when the temperature rises to 973 K, static recrystallization occurs. It is found that fine particles are precipitated when the TiNi alloy processed by ECAE is annealed at 773 K.

等通道球形转角膨胀挤压工业纯铝的剧烈塑性变形行为

提出一种耦合强塑性应变与高静水压力于一体的新型剧烈塑性变形工艺——等通道球形转角膨胀挤压(ECAEE-SC)。采用三维有限元数值模拟分析软件DEFORM-3D研究工业纯铝在ECAEE-SC变形过程中的塑性变形行为,分析材料流动、挤压载荷、等效应变和平均应力的分布规律,并与传统ECAE工艺进行比较。开展工业纯铝室温单道次ECAEE-SC变形验证实验,探讨材料显微组织和显微硬度的演变规律。结果表明,在ECAEE-SC变形过程中,材料内部处于理想的静水压力状态,挤压变形所需载荷较传统ECAE工艺时大幅增加。经单道次变形后,坯料内部累积塑性应变量达3.51且变形均匀性良好;工业纯铝晶粒得到显著细化,内部形成亚微米级等轴超细晶组织;材料显微硬度均匀分布,硬度值由初始铸态的HV 36.61提高到HV 70.20,增幅达91.75%。

等通道球形转角膨胀挤压工业纯铝的组织与性能

采用新型等通道球形转角膨胀挤压(equal channel angular expansion extrusion with spherical cavity,ECAEE-SC)工艺,对工业纯铝进行室温1道次挤压变形。借助光学显微镜(OM)、电子背散射衍射(EBSD)研究变形过程中工业纯铝显微组织的变化规律,并进行了硬度测试和拉伸试验。结果表明:ECAEE-SC工艺具有复合成形效果和较高的挤压效率,坯料成功实现了单道次连续变形。工业纯铝经1道次ECAEE-SC变形后,在机械剪切、应变累积和静水压力的共同作用下,晶粒显著破碎和细化,内部形成了大量细小、均匀的等轴亚晶,平均晶粒尺寸约为4.6mm;材料表现出优良的综合力学性能,HV显微硬度由未变形时的366 MPa增加至702 MPa,增幅为91.8%,且分布趋于均匀;抗拉强度高达183.8 MPa,而伸长率降低至12.7%,拉伸断口表现出明显的韧性断裂特征。