Papers by Author: Dong Liang Lin

Abstract: The Mg96Y3Zn1 alloy processed by equal channel angular pressing has been investigated. It was found that the Mg96Y3Zn1 alloy processed by ECAP obtained ultrafine grains and exhibits excellent mechanical properties. After ECAP, the average grain size of Mg96Y3Zn1 alloy refined to about 400 nm. The highest strengths with yield strength of 381.45MPa and ultimate tensile strength of 438.33MPa were obtained after 2 passes at 623K. It was found that cracks were preferentially initiated and propagated in the interior of X-phase during the tensile test. As a result, the elongation of alloy is decreased with pass number increasing.

Abstract: The effect of second-phase particles on the grain refinement of AZ61 and AZ91 Mg-Al-Zn alloys with different volume fractions of β-Mg17Al12 phase particles during equal channel angular extrusion (ECAE) has been investigated. The microstructure were observed by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which revealed that grain refinement was enhanced by second phase particles at initial stage of ECAE. And finer grains with the high angle grain boundaries (HAGBs) and disperse second-phase particles could be obtained in AZ61 and AZ91 after 8 passes of ECAE.

Abstract: The effect of second phase on the mechanical properties of AZ61 and AZ91 Mg-Al-Zn magnesium alloy processed by equal-channel angular extrusion (ECAE) has been investigated. The results revealed that cracks initiated at and propagated through the α-Mg/β-Mg17Al12 interfaces and grain boundaries of Mg-Al-Zn alloys during tensile deformation. For AZ61, the elongation increased with the increase of ECAE pass number and the decrease of grain size. However, the elongation of AZ91 with more second phase particles decreased with the increase of ECAE pass number and the decrease of grain size.

Abstract: The elevated temperature mechanical behavior of Mg-Y-Zn alloys was investigated. It was found that the extruded Mg-Y-Zn alloy exhibited excellent mechanical properties both at ambient temperature and elevated temperature. With the increase of tensile temperature, the ultimate tensile strengths of Mg-Y-Zn alloys decreased and their elongations increased. The ultimate tensile strengths increased and elongations decreased with the increase of yttrium content. However, a gradual increase in the ultimate tensile strength and elongation both at ambient temperature and elevated temperature was obtained by increasing both yttrium and zinc contents. The fracture modes of Mg-Y-Zn alloys at different tensile temperature were also investigated.

Abstract: Single roll drive equal channel angular process (SRD-ECAP) is derived from classical equal channel angular pressing (ECAP). It overcomes the drawbacks of ECAP, which is a discontinuous process and can only process short billets with invariable square or round section. SRD-ECAP, however, can process long billets continuously. In addition, it can also process sheet or strip. Another merit is that diameter or thickness of billets processed is adjustable. The structure of SRD-ECAP is quite simple and easy to be realized. In this paper, stress analysis has also been carried out. It is believed that SRD-ECAP can be a potential severe plastic deformation (SPD) process for Industrial Application.

Abstract: Microstructure evolution and mechanical properties of AZ31 Mg alloy during equal channel angular extrusion (ECAE) at the temperature range of 453-498K was investigated. The processing temperature is an important factor to affect the microstructure and mechanical properties of the Mg alloy during ECAE. ECAE processing can be practiced at 498k or upon the temperature for as-received AZ31 alloy. A new two-step ECAEed processing was successfully used with lowing the processing temperature to 453k. The ductility increased but yield stress decreased though the grain refinement after ECAE at 498k because the recrystallization took place and large angle grain boundary formed. However both the ductility and yield stress were increased after two-step ECAE, which was ascribed to grain refinement as well as incomplete dynamic recovery and recrystallization during the processing.