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<p>A frame-shaped casting was selected to investigate the effects of three types of molds on the microstructure and properties of Ti–6Al–4V titanium alloy castings, namely a ceramic shell mold, a machined graphite mold, and a specialized sand mold. To minimize the effects of temperature variations across molds and of the pouring temperature, these three molds were integrated into a single pouring system for simultaneous casting. After hot isostatic pressing (HIP), specimens were taken from typical positions of the castings using different molds and subjected to metallographic structure examination, room-temperature tensile and fatigue performance tests. Results indicate that the graphite mold casting exhibits the smallest grain size, <i>α</i> colonies, and <i>α</i> lamellar thickness. A substantial amount of basket-weave microstructure developed as a result of the high cooling rate during casting, which was induced by the high thermal conductivity and thermal effusivity of the graphite mold. The graphite mold castings exhibited the highest average tensile strength, yield strength, and elongation—reaching 955.4&#xa0;MPa, 861.2&#xa0;MPa, and 11.7%, respectively. The median fatigue strength of graphite mold castings is significantly higher than that of other casting types, approximately 18 times greater than investment castings and 25 times greater than sand castings. The outstanding fatigue performance can be attributed to the fine <i>β</i> grain size as well as the formed basket-weave microstructure with finer intersecting <i>α</i> lamellae. The fatigue fracture surface of graphite mold casting presents border crack propagation regions and narrower final fracture regions characterized by small cleavage facets and fine fatigue striations.</p>

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Effects of Mold Type on the Microstructure and Mechanical Properties of Ti–6Al–4V Titanium Alloy Castings

  • 期刊论文

  • 发表日期：

    2026年5月26日

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  • Qiangwei Xiao,
  • Zhijun Ji,
  • Shouyin Zhang,
  • Xin Feng,
  • Jianfeng Yin,
  • Zhiwei Jia,
  • Yuanguang Zhang,
  • Deji Wang,
  • Zhifeng Xu

摘要

A frame-shaped casting was selected to investigate the effects of three types of molds on the microstructure and properties of Ti–6Al–4V titanium alloy castings, namely a ceramic shell mold, a machined graphite mold, and a specialized sand mold. To minimize the effects of temperature variations across molds and of the pouring temperature, these three molds were integrated into a single pouring system for simultaneous casting. After hot isostatic pressing (HIP), specimens were taken from typical positions of the castings using different molds and subjected to metallographic structure examination, room-temperature tensile and fatigue performance tests. Results indicate that the graphite mold casting exhibits the smallest grain size, α colonies, and α lamellar thickness. A substantial amount of basket-weave microstructure developed as a result of the high cooling rate during casting, which was induced by the high thermal conductivity and thermal effusivity of the graphite mold. The graphite mold castings exhibited the highest average tensile strength, yield strength, and elongation—reaching 955.4 MPa, 861.2 MPa, and 11.7%, respectively. The median fatigue strength of graphite mold castings is significantly higher than that of other casting types, approximately 18 times greater than investment castings and 25 times greater than sand castings. The outstanding fatigue performance can be attributed to the fine β grain size as well as the formed basket-weave microstructure with finer intersecting α lamellae. The fatigue fracture surface of graphite mold casting presents border crack propagation regions and narrower final fracture regions characterized by small cleavage facets and fine fatigue striations.