Browsing by Author "Liu, X.W."

Now showing 1 - 2 of 2

Crack growth of 10M Ni-Mn-Ga material in cyclic mechanical loading
(2010) Aaltio, I.; Ge, Yanling; Pulkkinen, H.; Sjöberg, A.; Söderberg, O.; Liu, X.W.; Hannula, S.-P.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The 10M martensitic Ni–Mn–Ga single crystal materials are usually applied in the magneto-mechanical actuators. Therefore, it is important to know the possible effect of the long-term cyclic shape changes on their structure and behavior. This can be evaluated with the mechanical fatigue testing. In the present study, the single crystal 10M Ni–Mn–Ga samples of different compositions were applied to strain-controlled uniaxial mechanical cycling in the multivariant state at ambient temperature. The experiments revealed distinctive changes of the twin variant structure, especially in the mobile twin area, density of twin boundaries, and in the tendency for fatigue crack growth. Characterization of the crack surface showed that the cracks in the microscale grow in a step-wise manner on specific crystallographic planes, i.e, twin boundary planes, but that the macroscopic crack does not occur only along crystallographic directions.
The Microstructural Effects on the Mechanical and Thermal Properties of Pulsed Electric Current Sintered Cu-Al2O3 Composites
(2011) Ritasalo, R.; Liu, X.W.; Söderberg, O.; Keski-Honkola, A.; Pitkänen, V.; Hannula, S-P.
A4 Artikkeli konferenssijulkaisussa
In this work, the influences of the microstructure on the mechanical and thermal properties of pulsed electric currentsintered (PECS) Cu-Al2O3 composites are investigated. The process parameters were optimized for four different grades ofcomposite powders to obtain dense samples (98-99.6%T.D.). Higher hardness and better thermal stability were attained tothe samples compacted from commercial internally oxidized (IO) powders than to the compacts made from the chemicallysynthesised experimental powders. This difference was attributed to the distribution and size of Al2O3-particles in the twotypes of composites. The CTE values of all the compacts were between 17 and 20 x 10-6K-1 (370-770 K). The results showthat PECS can be used to produce dense high quality Cu-Al2O3 composites.