ABSTRACT 7075 alloys were prepared using metals of 99.99% high purity in the vacuum atmosphere. These alloys were directionally solidified upwards under various growth velocities (8.3–166.0 μm/s) using a Bridgman-type directional solidification furnace. Dendritic spacings (λ1, λ2) and microhardness (HV) were measured from both longitudinal and transverse sections of the samples. Ultimate tensile strength (σU) and yield strength (σy) of the solidified samples at room temperature were examined. The HV increased from 75.2 to 112.8 MPa, the σU increased from 155.8 to 210.1 MPa, and the σy increased from 198.4 to 319.8 MPa with increasing growth velocity from 8.3 to 166.0 μm/s. Exponent values of the V for the λ1, λ2, HV, σU and σy were calculated as 0.27, 0.41, 0.05, 0.11 and 0.15, respectively. The results show that the hot tearing in the 7075 alloy is caused by the fracture of dendrites structures.

中文翻译：

---

生长速度对定向凝固7075合金组织和力学性能的影响

摘要 7075 合金是在真空气氛中使用 99.99% 高纯度金属制备的。这些合金使用布里奇曼型定向凝固炉在各种生长速度（8.3-166.0 μm/s）下向上定向凝固。从样品的纵向和横向截面测量枝晶间距 (λ1, λ2) 和显微硬度 (HV)。检查了室温下固化样品的极限拉伸强度 (σU) 和屈服强度 (σy)。随着生长速度从8.3增加到166.0 μm/s，HV从75.2增加到112.8 MPa，σU从155.8增加到210.1 MPa，σy从198.4增加到319.8 MPa。λ1、λ2、HV、σU 和 σy 的 V 指数值分别计算为 0.27、0.41、0.05、0.11 和 0.15。