Plastic deformation of icosahedral Al-Pd-Mn single quasicrystals - I. Experimental results

In order to compare plastic deformation along different loading axes, icosa hedral Al-Pd-Mn single quasicrystals were deformed in uniaxial compression along twofold and fivefold axes, between the lowest temperatures where defo rmation at strain rates of 10(-5) and 10(-4) s(-1) was possible and 820 deg rees C. For the first time, experiments were performed below 680 degrees C. The strain rate and temperature sensitivity of the flow stress were studie d by stress relaxation and temperature change tests. In a range of strain o f steady state deformation following a yield drop, the flow stress and its strain rate sensitivity increase strongly with decreasing temperature. The temperature sensitivity shows a maximum at about 700 degrees C. The data ha rdly depend on the specimen orientation. Repeated relaxation tests indicate changes in the microstructure during the relaxations. Transient phenomena also occurred when the relaxation tests had not been started from steady st ate deformation, e.g. before the upper yield point, after long relaxations or after unloading. The results will be discussed in Part II of this paper.