Internal Friction/Attenuation in a β‐Spodumene Glass‐Ceramic

Transient creep and attenuation (internal friction) of a β‐spodumene glass‐ceramic has been examined. Four‐point flexural creep tests have been performed at high tempera‐ture(T = 925°‐1000°C) and modest stress levels (σ l,max = 7‐25 MPa). The flexural creep response of the glass‐ceramic is characterized by a large decelerating transient that precedes the establishment of a steady state. The creep response is transformed via a numerical algorithm to give the attenuation spectrum. In addition, low‐stress (2.5‐30 MPa), subresonant‐frequency (10 −5 Hz ≤ f ≤ 1 Hz), com‐pression‐compression attenuation experiments have been performed. A first‐order thermodynamic analysis of the effect of effective pressure on the volume fraction of re‐sidual glass suggests that the dilatational process that is associated with the flexural deformation mode should be characterized by a single loss mechanism. The predictions that are available from the flexural creep tests, as well as those that have been directly measured in experiments, in‐dicate that attenuation behavior is insensitive to both fre‐quency and temperature and exhibits a characteristic band of absorption. The weak frequency dependence of this an‐elastic response is well‐characterized by a power law of the form Q −1 χf α , where 0.15 ≥ a ≥ 0.3, which suggests a physical mechanism that possesses a distribution of relax‐ation times. A plausible explanation exists in the fluid‐mechanics description of deformation‐induced melt migra‐tion, in which the crystalline β‐spodumene “matrix” undergoes compaction or dilatation while the residual glass phase, which forms an interpenetrative network along grain triple junctions of the matrix, flows: the evolution with time of the compacted (and/or dilated) layer thickness of the deforming matrix produces a distribution of compli‐ances.