Grain refinement of primary silicon in hypereutectic Al-Si alloys by different P-containing compounds

The grain refinement behavior of Si-3 P,Si-25 Mn-10 P,and Al-10 Si-2 Fe-3 P master alloys on hypereutectic Al-24 Si alloy was studied.Microstructure analysis indicates that the P-containing compounds in the three master alloys are Si P,Mn P,and Al P,respectively.The coarse flower-like primary silicon in the Al-24 Si alloy transforms into smaller,well-distributed blocks with the addition of various master alloys.When pouring at 840°C,the average grain size of the primary silicon refined by Si-25 Mn-10 P master alloy with a holding time of 30 min is about 18μm,which is significantly smaller than those refined by Si-3 P and Al-10 Si-2 Fe-3 P master alloys.The grain size shows an increasing trend when the holding time is further prolonged.Higher holding temperature has a positive effect on the grain refinement of Si-25 Mn-10 P master alloy.The grain refinement mechanism of the three master alloys was also discussed.

化解产能过剩政策对重工业城市房地产需求的影响研究

以房地产需求影响因素和产能过剩相关理论为基础,分析化解产能过剩政策影响重工业城市房地产市场需求的传导机制,并基于房地产百城数据,构建差分模型进行实证检验。结果表明,化解产能过剩政策对重工业城市房地产需求具有显著的负向影响,但这种影响具有时效性,且对住宅市场的影响更为显著。应从企业职工安置、购房金融支持、优化产业布局等方面提高居民购房能力,实现重工业城市'去产能'与'去库存'并举。