MECHANICAL-BEHAVIOR AND MICROCRACKING OF CUBIC TERNARY ZIRCONIUM TRIALUMINIDES

Vickers microhardness, compressive properties from room temperature (RT) to 900-degrees-C, and microcracking development of cubic ternary zirconium trialuminides macroalloyed with Cu (Al-12.5Cu-25Zr), Mn (Al-9Mn-25Zr), and Cr (Al-8Cr-25Zr) (atomic percent) were investigated. It is shown that microhardness exhibits a strong dependence on load. It does not depend in any systematic way on the atomic number of macroalloying element (Cu, Mn, or Cr) but seems to be affected by the zirconium content. It is also found that the yield stress exhibits a strong positive dependence on temperature particularly in Al-9Mn-25Zr and Al-12.5Cu-25Zr. Microcracking experiments have shown that microcracks nucleate in many instances on pre-existing micropores. To a large extent, the proliferation of cracks also occurs by connecting the pores. It is observed that the work-hardening rate at room temperature is very high for cubic Al3Zr-base intermetallic alloys, being in the range 20 to 30 GPa. It decreases with increasing temperature up to 400-degrees-C to 500-degrees-C and then slightly increases up to 900-degrees-C.