Plastic properties and ferroelastic twinning of (CH3)2NH2Al(SO4)2.6H2O crystals

Plastic deformation of DMAAS crystals is studied over a broad temperature range. As the temperature decreases, the flow limit increases and a break occurs at 110 K in the function σ 0.2 (T). Mechanical stress in the ferroelectric phase produces ferroelastic twinning; however, slippage is absent up to deformations exceeding 15%. A model is proposed for the crystal structure of the twin that explains well the observed plastic properties of the DMAAS crystals