Characteristics of interfacial reactions between Ti-6Al-4V alloy and ZrO2 ceramic mold

Abstract

The interfacial reaction between Ti-6Al-4V alloy and ZrO 2 ceramic mold with zirconia sol binder was investigated by keeping the 12 g alloy melt in a vacuum induction furnace for 15 s. The microstructures, element distribution and phase constitution of the interface were identified by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results show that the whole interface reaction layer can be divided into three regions: metal penetration layer, transition layer, and hardened layer according to the structure morphology, which has the characteristics of severe metal penetration, finer lamellar, and coarse oxygen-rich α phase, respectively. The erosion of the alloy melt on the ceramic mold promotes the decomposition of zirconia, which leads to the increase of local Zr concentration, greatly increasing the activity coefficient of Ti, aggravating the occurrence of interfacial reaction. Thus, the interfacial reaction shows the characteristics of chain reaction. When the oxygen released by the dissolution of zirconia exceeds the local solid solubility, it precipitates in the form of bubbles, resulting in blowholes at the interface. The result also indicates that the zirconia mold with zirconia sol binder is not suitable for pouring heavy titanium alloy castings.

Effect of heat treatment on microstructure, mechanical and tribological properties of in-situ (TiC+TiB)/TC4 composites by casting

“…Furthermore, the β to α transformation is not complete, resulting in a small amount of transformed β distributed among the α phase, forming a basketweave structure with a uniform distribution of α and transformed β phases. This structure is beneficial for enhancing the fracture toughness and preventing fatigue crack extension of TMCs [34] . After HT1 heat treatment, the morphology of TiB remains basically unchanged, while TiC gradually granulates.…”

Problems of Materials Choice for Ceramic Molds to Obtain Titanium Alloys Shape Castings

“…Багато робіт [13][14][15][16] присвячено дослідженню взаємодії титану з керамічними формами на основі ZrO 2 , чистого або стабілізованого оксидами CaO чи Y 2 O 3 . У роботі [13] відзначається, що характер взаємодії титану і ZrO 2 залежить від типу стабілізатора та його кількості, зокрема встановлено, що додавання 5 мол.% CaO демонструє найкращі показники (порівняно з 9 та 17 мол.% CaO) завдяки формуванню тонкого шару TiO, який поводиться як дифузійний бар'єр між Ti та ZrO 2 .…”

Archives of Foundry Engineering

“…A lot of works is devoted to the study of the interaction of titanium with various materials of ceramic molds [15][16][17][18][19][20][21][22][23][24], but in most studies the conditions of experiments differ (metal melting methods, sample weight, alloy grade, atmosphere in which the pouring was performed), and therefore the results -the thickness of the reactive layer of titanium products for the same materials of ceramic molds may differ by an order of magnitude. Melting and pouring of titanium in an electron-beam foundry takes place under high vacuum conditions (≤ 1.33 Pa), which can cause thermal dissociation of mold refractory oxides and as a result affect the nature of the interaction of ceramic molds with titanium melt.…”