The Research On The Microstructures And Mechanical Properties Of ZA60 Alloys By Solid-Liquid Mixed Casting

The ZA60 ingots were fabricated by solid-liquid mixed casting technology, the microstrctures of ZA60 alloys were researched in different fusant degree of superheat,powder addition and powder particle size, and the technological parameters of solid-liquid mixed casting of ZA60 alloys were optimized. At the same time, the microstrctures evolution regularity of ZA60 alloys was discussed in metal casting,semi-solid casting and solid-liquid mixed casting; the average grain size and the volume fraction of primaryαphase were measured by using TCL metallographical analysis software. The phases of ZA60 alloys were analyzed. The hardness,room temperature tensile-strength and high temperature tensile-strength of ZA60 alloys were studied in the last. Through these studies, results were concluded as below:1. The grain size of ZA60 alloys in metal-casting was larger than semi-solid casting and solid-liquid mixed casting, the grain size of ZA60 alloys was refined and spheroidized in a certain extent in semi-solid casting, the grain size of ZA60 alloys in solid-liquid mixed casting was refined and spheroidized best, and morphology was homogeneous. The microstructures were studied in different technological parameters (fusant degree of superheat,power patical size,powder addition) in the process of solid-liquid mixed casting, considerations in grian size and uniformity, when the fusant degree of superheat was 40℃,the power patical size was -200～+400 mesh and the powder addition was 40% , the microstructures of ZA60 alloys were better refined and spheroidized.2. The phases of ZA60 alloys included:α(aluminum rich)phase,β(Al base sosolid)phase,η(znic rich)phase andε(intermetallic compound)phase. The same phases were formed in metal-casting,semi-solid casting and solid-liquid mixed casting, but the quantity of the phases was different, in the three casting techniques, the primaryαphase quantity in semi-solid casting was more than the metal-casting, in the solid-liquid mixed casting theαphase quantity was most. In the process of solid-liquid mixed casting, different technological parameters had important effect on primaryαphase, the higher the fusant degree of superheat was, the less the primaryαphase quantity; the more th powder addition was, the more the primaryαphase quantity was; the smaller the powder size was, the more the primaryαphase quantity was. The quantity of primaryαphase was relative to the cooling velocity of the solidification, at the same time, it was relative to increase of the nonuiform nucleation partical which was supplied by added powder.3. The room-temperature tensile strength of ZA60 alloys which fabricated by solid-liquid mixed casting was highest(415Mpa), semi-solid casting was higher(360Mpa), and the metal casting was lowest(285Mpa). Elongation of ZA60 alloys which fabricated by solid-liquid mixed casting was highest(6.0%), semi-solid casting was higher(3.5%), and the metal casting was lowest(1.2%). The fracture mechanics of ZA60 alloys was brittle fracture, the cleavage feature existed in the fracture of metal casting, besides the cleavage setback existed in the fracture of semi-solid casting and solid-liquid mixed casting, there were some tearing arris in the fracture, it had the feature of quasi-cleavage.4. The high-temperature strength of the ZA60 alloys which was fabricated by metal-casting was higher than semi-solid casting and solid-liquid mixed casting. In the same rate of extension(6.67×10-5s-1), the higher the tensile temperature, the lower the tensile strength of ZA60 alloys was, in the same tensile temperature(200℃), the higher the rate of extension was, the higher the tensile strength of ZA60 alloys was. The fracture of ZA60 alloys of metal-casting was intercrystalline cracking,semi-solid casting was quasi-cleavage crack and the crack features of solid-liquid mixed casting was cleavage. They were brittle facture.