α板条排列方式对电子束熔丝沉积TC4钛合金组织与拉伸性能的影响

Effect of α Plate Arrangement in EBRM TC4 Titanium Alloy on Microstructure and Tensile Properties

研究了电子束熔丝沉积(EBRM)TC4钛合金堆积体横截面的低倍、高倍组织特征及不同特征位置的拉伸性能。结果表明,TC4钛合金堆积体低倍组织呈柱状晶形貌,随着堆积高度增加,柱状晶宽度逐渐增加,晶内组织有从模糊晶向清晰晶转变的趋势。高倍显微镜下模糊晶区α板条呈编织状排列,清晰晶区α板条呈平行排列并形成粗大集束。α板条的排列方式对拉伸强度影响较小,但对塑性影响较大。平行排列的α集束内易产生局部变形,导致清晰晶区拉伸塑性较低。

Macrostructure, microstructure and tensile properties of TC4 titanium alloy which produced by the electron beam rapid manufacturing method(EBRM) were investigated. The results show that the macrostructure of EBRM TC4 titanium alloy is columnar crystal. From the bottom to the top, the width of the prior β column increases and the macrostructure transites from indistinct to distinct. At high magnification, a basket-weave arrangement of α plates is in the bottom as indistinct zone whereas a parallel arrangement of α plates is in the top as distinct zone. The snow-like structure is found in the distinct zone and the zone is resulted from large α colonies with parallel α plates. It can be found that α plate arrangement has relatively limited effects on the tensile strength while it has strong influences on the tensile ductility. Lower ductility in the distinct zone is attributed to the liability of local concentrated deformation in large α colonies with parallel α plates.