Impression creep behavior of cast Pb–Sb alloys

2010

Metall Mater Trans A

Self Cite

The effects of 0.2, 0.6, and 1.0 wt pct Zr additions on the microstructure and creep behavior of AZ91 Mg alloy were investigated by impression tests carried out under constant punching stress (r imp ) in the range 100 to 650 MPa, corresponding to the modulus-compensated stress levels of 0:007 r imp G 0:044, at temperatures in the range 425 K to 570 K (152°C to 297°C). The alloy containing 0.6 wt pct Zr showed the best creep resistance mainly due to the favorable formation of Al 3 Zr 2 and Al 2 Zr intermetallic compounds, reduction in the volume fraction of the eutectic b-Mg 17 Al 12 phase, and solid solution hardening effects of Al in the Mg matrix. Based on the obtained stress exponents of 4.2 to 6.5 and activation energies of 90.7 to 127.1 kJ/mol, it is proposed that two parallel mechanisms of lattice and pipe-diffusion-controlled dislocation climb compete. Dislocation climb controlled by dislocation pipe diffusion prevails at high stresses, whereas climb of edge dislocations is the controlling mechanism at low stresses.

Section: Methodsmentioning

confidence: 99%

Effects of Zr Additions on the Microstructure and Impression Creep Behavior of AZ91 Magnesium Alloy

Kabirian

2010

Metall Mater Trans A

Self Cite

“…The details of the testing arrangement are explained elsewhere 19,20 and will only be briefly described here. An MTS universal tensile testing machine equipped with a three-zone split furnace was used to perform constant-load impression tests.…”

Section: Impression Creep Testsmentioning

confidence: 99%

“…This has been achieved using the impression creep testing technique, which has been widely used in the creep study of various solder materials. [17][18][19][20][21] EXPERIMENTAL PROCEDURE…”

Section: Introductionmentioning

confidence: 99%

Effects of Ag and Al Additions on the Structure and Creep Properties of Sn-9Zn Solder Alloy

Geranmayeh

Noori

et al. 2008

Journal of Elec Materi

Self Cite

Creep behavior of the eutectic Sn-9Zn, Sn-9Zn-0.5Ag, and Sn-9Zn-0.5Al solder alloys was studied by impression testing under constant punching stress in the range of 60 MPa to 130 MPa and at temperatures in the range of 298 K to 370 K. Analysis of the data showed that, for all loads and temperatures, Sn-9Zn-0.5Al had the lowest creep rates and thus the highest creep resistance among all materials tested. The creep resistance of Sn-9Zn-0.5Ag was slightly lower than that of the Al-containing alloy. The enhanced creep behaviors of the ternary alloys are attributed to the presence of AgZn 3 and very fine Zn particles, which act as the main strengthening agents in the Sn-9Zn-0.5Ag and Sn-9Zn-0.5Al alloys, respectively. Assuming a power-law relationship between the impression rate and stress, average stress exponents of 6.9, 7.1, and 7.2 and activation energies of 42.1 kJ mol -1 , 42.9 kJ mol -1 , and 43.0 kJ mol -1 were obtained for Sn-9Zn, Sn-9Zn-0.5Ag and Sn-9Zn-0.5Al, respectively. These activation energies are close to 46 kJ mol -1 for dislocation climb, assisted by vacancy diffusion through dislocation cores in the Sn. This, together with the stress exponents of about 7, suggests that the operative creep mechanism is dislocation climb controlled by dislocation pipe diffusion.

“…The details of the testing arrangement are explained elsewhere [20] and will be described here only briefly. An MTS (MTS Systems Corporation, Eden Prairie, MN) universal tensile testing machine equipped with a three-zone split furnace was used to perform constant-load impression tests in the air atmosphere.…”

Section: B Impression Creep Testsmentioning

confidence: 99%

Microstructure and Impression Creep Characteristics of Cast Mg-5Sn-xBi Magnesium Alloys

Keyvani

Nayyeri

2010

Metall Mater Trans A

The microstructure and creep behavior of a cast Mg-5Sn alloy with 1, 2, and 3 wt pct Bi additions were studied by impression tests in the temperature range 423 K to 523 K (150°C to 250°C) under punching stresses in the range 125 to 475 MPa for dwell times up to 3600 seconds. The alloy containing 3 wt pct Bi showed the lowest creep rates and, thus, the highest creep resistance among all materials tested. This is attributed to the favorable formation of the more thermally stable Mg 3 Bi 2 intermetallic compound, the reduction in the volume fraction of the less stable Mg 2 Sn phase, and the dissolution of Bi in the remaining Mg 2 Sn particles. These particles strengthen both the matrix and grain boundaries during creep deformation of the investigated system. The creep behavior of the Mg-5Sn alloy can be divided into the low-and high-stress regimes, with the respective average stress exponents of 5.5 and 10.5 and activation energies of 98.3 and 163.5 kJ mol À1 . This is in contrast to the creep behavior of the Bi-containing alloys, which can be expressed by a single linear relationship over the whole stress and temperature ranges studied, yielding stress exponents in the range 7 to 8 and activation energies of 101.0 to 107.0 kJ mol À1 . Based on the obtained stress exponents and activation energies, it is proposed that the dominant creep mechanism in Mg-5Sn is pipe-diffusion controlled dislocation viscous glide the low-stress regime and dislocation climb creep with back stress in the high-stress regime. For the Mg-5Sn-xBi alloys, however, the controlling creep mechanism is dislocation climb with an additional particle strengthening effect, which is characterized by the higher stress exponent of 7 to 8.