Development Of Zn-base Alloy ZA30 With High Strength & Toughness And Study On Its Wear Properties

Owing to lower melting temperature and less industrial pollution of zinc-based alloy, replacement for copper alloy helps to achieve energy saving, emission reduction and sustainable development. However, current developed zinc-based alloys at domestic and abroad has lower plasticity at room temperature, therefore, parts made of the alloy often lose effectiveness due to premature rupture, which becomes an bottleneck to wide application of zinc-based alloy. Developing zinc-based alloy with higher strength and plasticity has academic significance and application value.Through research of the effects of Al, Cu, boron-titanium composite salt modification and RE modification on the mechanical properties of zinc-based alloys, a new zinc-based alloy ZA30 with 407-418MPa tensile strength and 12.1%～17.3% elongation has been developed. It is found that when aluminum content lies between 27%～35%, tensile strength of zinc-based alloy gradually reduces while the elongation rises initially, and gradually drops with maximum around 29%～31%. This is a combined consequence of increasing strength and elongation due to a (Al) phase increment and reduction of non-equilibrium eutectics, decreasing strength and elongation from reduction in (α+η) eutectoids and micro-shrinkage increment. It is also noticed that when copper content lies between 1.5%～3.5%, tensile strength of zinc-based alloy gradually increases while the elongation rises initially, and gradually drops with maximum around 2%～2.5%. Modification of boron-titanium compound salt or Rare Earth on zinc-based alloy, could refine microstructure, and evenly and discontinuously distribute non-equilibrium eutectic, which increases tensile strength and significantly increases elongation. In terms of modification effect, boron-titanium composite salt is superior to RE.Comparative study on wear resistance of 5 sliding-bearing alloys, such as ZA30, ZA27, ZCuSn6Zn6Pb3, ZCuA110Fe3 and ZCuSn10P1 was performed under different lubrication and loads on MPX-2000 wear tester, which provides an experimental verification for ZA30 applications. The results show that under the 2# lithium grease lubrication and the load of 200N,400N respectively, ZA30 wear resistance is superior to the other four kinds of alloys. Under 46# gear oil lubrication and the load of 400N, 600N,800N,1000N respectively, ZA30 shows obviously superior wear resistance than ZA27, ZCuSn6Zn6Pb3, ZCuAL10Fe3, and slightly better than ZCuSn10P1, except that ZA30 is slightly lower than ZCuSn10P1 at 1000N. Based on the above results, more than 10 site tests have been carried out and the lab conclusions have been verified.With scanning electron microscopy and X-ray spectroscopy, wear mechanism of five kinds of alloys have been explored. The after-wearing SEM morphology shows that under the same experimental conditions, ZA30 has more shallow wear traces than that of the other four kinds of alloys, which is consistent with the results in the above friction and wear comparative tests. Wear morphology also shows that as the load increases, abrasive wear transforms to adhesive wear in five alloys. X-ray spectrum analysis confirms the existence of transfer film and chemical reaction film of ZA30 and three copper alloys on the grinding surface of steel plate.Through further analysis and induction for wear test data, it is found that abrasive wear should be sub-divided into plow-type abrasive wear and spall-type abrasive wear, and wear resistance of plow-type abrasive wear is better than that of spall-type abrasive wear. It is also found that when ZA30, ZCuSn6Zn6Pb3, ZCuA110Fe3 and ZCuSn10P1 are all in low wear condition, the order of wear resistance is ZA30> ZCuSn10P1> ZCuSn6Zn6Pb3> ZCuAL10Fe3, with change of load, sliding velocity, lubrication, etc, the wear condition would transfer from low wear to severe one, the order of transfer is ZCuSn6Zn6Pb3> ZCuSn10P1> ZA30> ZCuAL10Fe3, the order of wear resistance changes correspondingly.