铸造工艺对钛合金Ti5Al2.5Sn ELI铸态组织及性能的影响

Influence of Casting Process on Structure and Mechanical Properties of As-cast Ti5Al2.5Sn ELI Titanium Alloy

Ti5Al2.5Sn ELI钛合金是航空航天等领域重要的结构材料。本工作采用3种铸型同炉浇注的方法研究了铸造工艺对该合金铸态组织和室温拉伸性能的影响。结果表明,该合金石墨型铸造试样表面粗糙,陶瓷型和金属型的则较光滑;石墨型试样宏观组织为大量等轴晶和少量柱状晶,金属型的为少量等轴晶和大量柱状晶,陶瓷型的为粗大柱状晶和等轴晶;不同工艺下显微组织均由不规则边界α集束组成,其内部为片状α相,石墨型的α片宽度最小,金属型的次之,陶瓷型的最大;该合金铸态抗拉强度715~731 MPa、伸长率8%~15%,石墨型的伸长率最高,金属型的次之,陶瓷型的最低,铸造工艺对该合金塑性影响强烈,但对强度的影响较小;铸型表面形貌、导热系数、α集束大小及α片厚度的不同是上述现象产生的主要原因。

Titanium alloy Ti5 Al2.5 Sn ELI is an important structural material in the field of aerospace. In this research, the influence of casting process on the as-cast structure and tensile properties of titanium alloy Ti5 Al2.5 Sn ELI at room temperature was studied by pouring one furnace alloy with three kinds of mold. The results show that the surface of casting samples from the graphite mold is rough, while that from the ceramic and metal mold is smooth;the macrostructure of samples from graphite mold is composed of numbers of equiaxed crystals and some columnar crystals, while that from the metal mold consists of some equiaxed crystals and numbers of columnar crystals, and that from ceramic mold consists of numbers of columnar crystals and a few equiaxed crystals;the microstructure of the alloy under different processes is composed of irregular boundary α cluster, the inner part is composed of sheet α phase;the width of α sheet of sample from the graphite mold is the smallest, that from the metal mold is in the middle, and that from the ceramic mold is the largest;the tensile strength of alloy is 715~731 MPa;the elongation is 8%~15%, the elongation of samples from the graphite mold is the highest, that from the metal mold is the second, and that from the ceramic mold is the lowest. The influence of molds on the elongation is obvious, but that on the strengths is relatively not;the difference of surface morphology and thermal conductivity of the mold, and the difference of α cluster size and α sheet thickness of samples are the main reasons for the phenomena.